Gnn miccrozonation vol 1

Consultant in
Geophysics, Geology, & Seismic Studies
Cell: 0300-5478842 & 0342-2940921
GILGIT NOMAL AND NALTAR
MASTER PLAN 2040
MM PAKISTAN (Pvt) Ltd.
SEISMIC MICROZONATION STUDIES
Volume-1
DECEMBER 2019
PREPARED BY
SYED KAZIM MEHDI

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TABLE OF CONTENTS
Page No.
1.0 GENERAL 1
2.0 LOCATION OF GILGIT, NOMAL AND NALTAR CITY 2
3.0 GEOLOGY OF GILGIT, NOMAL AND NALTAR REGION 4
3.1 Geology of Gilgit, Nomal and Naltar City 5
4.0 SEISMOTECTONIC SETTING OF NORTHERN PAKISTAN 9
5.0 FAULT SYSTEM OF NORTHERN PAKISTAN 14
5.1 Kohistan Faults 15
5.2 Main Karakoram Thrust 15
5.3 Main Mantle Thrust 15
5.4 Main Boundary Thrust 16
6.0 SEISMOTECTONIC OF GILGIT BALTISTAN 16
6.1 Seismotectonic of Gilgit, Nomal and Naltar Region 16
7.0 DEVELOPMENT OF EARTHQUAKE DATA CATALOGUE 19
7.1 Catalogue Compilation 20
7.2 Historical Seismic Data Catalogue 21
7.3 Working File 21
7.4 Instrumental Seismic Data Catalogue 22

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8.0 ANALYSIS OF SEISMIC DATA 23
9.0 PRINCIPLES OF SEISMIC MICROZONATION 25
10.0 BUILDING CODE OF PAKISTAN 26
10.1 Soil Profile Type 26
11.0 METHODOLOGY OF PROBABILISTIC SEISMIC HAZARD ANALYSIS 27
11.1 Technical Framework 30
11.2 Recurrence Relationship and Seismicity Models 31
12.0 ATTENUATION RELATIONSHIP 32
12.1 Predictive Relationship 33
12.2 Attenuation Model 34
12.3 Implementation 36
13.0 PSHA OF GILGIT, NOMAL AND NALTAR 39
13.1 Identification and Characterization of Seismic Sources 39
13.2 Recurrence Relationship and Seismicity Models 39
14.0 SEISMIC PROVINCES AND AREA SOURCE ZONES 40

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14.1 Kohistan Seismic Zone 41
14.2 Hindukush Seismic Zone 42
14.3 Pamir Seismic Zone 43
14.4 Chitral Seismic Zone 43
14.5 Ladakh Seismic Zone 43
14.6 Main Karakoram Thrust (MKT) Seismic Zone 43
14.7 Karakoram Seismic Zone 43
14.8 Himalaya Seismic Zone 43
14.9 Nanga Parbat Haramosh Massif Seismic Zone 43
15.0 SEISMIC PARAMETERS 44
15.1 Focal Depths 44
16.0 SEISMIC MICROZONATION MASTER PLAN 2040 45
16.1 Classification of Areas for Microzonation of Gilgit, Nomal & Naltar 48
16.2 Seismic Hazard Analysis 50
16.3 Results of PSHA 51
16.4 Naltar III Hydropower Project 57
16.5 Hanzel Hydropower Project 57
16.6 Nespak Report on Seismic Zoning of Gilgit Baltistan 57
17.0 SEISMIC MICROZONES FOR MASTER PLAN 2040 59
18.0 MICRO SEISMIC MONITORING SYSTEM 69
19.0 CONCLUSIONS 70

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LIST OF FIGURES
Figure-1. Regional tectonic map showing the major fault systems in Northern Pakistan.
Figure-2. Location of Gilgit-Nomal &Naltar City.
Figure-3. Geology of Gilgit-Naltar Region.
Figure-4. Junction of Karakoram, Hindukush and Himalaya Mountain Ranges near Gilgit.
Figure-5. Blue Lake in Naltar Formed by Landsliding/Rocksliding.
Figure-6 Generalized Geological Map of Gilgit-Nomal and Naltar.
Figure-7 Indian Plate Colliding with Eurasian Plate.
Figure-8 Major tectonics in Pakistan (courtesy: Geological Survey of Pakistan).
Figure-9. The regional seismicity of Southern Asia (above magnitude 3.0)
Figure-10. Seismotectonic Fault System of Northern Pakistan.
Figure-11. Seismotectonic Model of Northern Pakistan.
Figure-12. Seismic Zoning Map of Pakistan.
Figure-13. Seismotectonic Map of Gilgit-Naltar Region and Locations of Major Earthquakes.
Figure-14. Seismicity within Gilgit-Naltar Region (300 km radial distance off Gilgit).
Figure-15. Earthquake re-occurrence function.
Figure-16. Coordinates of Seismic Zones in Gilgit, Nomal & Naltar.
Figure-17. Seismic Zones in Gilgit, Nomal and Naltar (GNN) Region.
Figure-18. Location of Duo Pani Area of Gilgit city.
Figure-19. Map Showing Different Area Connection of Gilgit City.
Figure-20. Total Hazard Curve and Uniform Spectra at Gilgit Central, Jutial, Dynor-KIU
Gilgit-KKH Road Intersection Vs30 750 m/sec, 475 Years Return Period.

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Figure-21. Total Hazard Curve and Uniform Spectra at Nomal Valley
Vs30 750 m/sec, 475 Years Return Period.
Figure-22. Total Hazard Curve and Uniform Spectra at All Six Seismic Units
‘
Figure-25. PGA Contour Map from Building Code of Pakistan (Seismic Provision 2007)
Value for Gilgit, Nomal Valley and Naltar Valley is 0.24g.
Figure-26 Seismic Microzonation of Gilgit for Return Period of 475 Years.
Figure-27. Seismic Microzonation of Gilgit for Return Period of 975 Years.
Figure-28. Seismic Microzonation of Gilgit for Return Period of 2475 Years.
Figure-29. Seismic Microzonation of Nomal for Return Period of 475 Years.
Figure-32 Seismic Microzonation of Nomal for Return Period of 475 Years.
Figure-33 Seismic Microzonation of Naltar for Return Period of 975 Years.
Figure-34 Seismic Microzonation of Naltar for Return Period of 2475 Years.

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EXECUTIVE SUMMERY
This report deals with the seismic microzoning of Gilgit, Nomal/Naltar for Master Plan 2040.
According to Building Code of Pakistan (Seismic Provision 2007), this area is placed in
seismically active Zone 3, while in its close vicinity there more active area of Seismic Zone 4.
Based on the geological reports/maps, geophysical data/reports, satellite imaginary and desktop
study of research papers, the area is divided into nine Seismic Zone. All Seismic Zones are active
with maximum earthquake potential of Mw 7.5 to Mw 8.0.
Historical earthquake data catalogue for Pakistan and composite instrumental seismic data
catalogue of Gilgit and Nomal/Naltar (GNN) Region are developed for the studies. The area of
300 km. radial distance from Gilgit is GNN Region for this report. Study of historical catalogue
indicates that Gilgit and Nomal/Naltar have experienced earthquake Intensity upto VIII, while
seismic events upto Mw 6.3 have originated from the area.
To determine the Soil Profile Types in accordance with Table 4.1 of BCP, the area is classified
into six seismic units. The most useful way of presenting the result is in terms of horizontal
hazard curves and spectra. Figures for different return periods, i.e. for 475, 975 and 2475 years,
relating estimated ground motion to annual exceedance probabilities which are the inverse of
return periods in years. In accordance with recommendations of BCP the Probabilistic Seismic
Hazard Analysis (PSHA) was carried out using single site EZ-FRISK software developed by
Fugro Engineering Consultants, USA.
Computed horizontal Peak Ground Acceleration (PGA) in terms of g through the latest state of
art FZ RISK software, along the six seismic units of Gilgit, Nomal and Naltar, are presented in
Table-2. The g value in case of Vs30 = 750 m/sec (dense soil/soft rock) is 0.24g at seismic units
of Naltar Valley and Nomal Valley while it is 0.25g at other four seismic microzones of Gilgit.
The structures can be safely constructed after accessing the condition of material present at the
desired location and according to g value given in Table-2 of this report.
For SB (dense soil/soft rock) = 750 m/sec the seismic value at Gilgit is 0.25g while at
Nomal/Naltar it is 0.24g. Available areas with such properties are best suitable for further
growth/developments. However, the areas with SD type (stiff soil) are least suitable and may be
avoided for further developments.

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It is concluded that the seismic values of g in this report are in accordance with the seismic
values adopted at Naltar Hydropower Project, Hanzel Hydropower Project and BCP.
Seismic microzones have been marked on GIS based Maps presented in Figure-26 through
Figure-34 for different return periods.
The Gilgit, Nomal and Naltar area is placed in Seismic Zone 3 and in its close vicinity is Seismic
Zone 4. Therefore it is recommended to install a Micro Seismic Monitoring System (MSMS)
with ANTELOPE Software (for data processing/analysis), for seismic safety monitoring
purposes. M/S Kinemetrics Inc. USA is the most suitable manufacturer of MSMS and
ANTELOPE Software. The company has already installed such networks in close vicinity of
Bunji, Skardu and Diamer Basha, Skardu and Chitral, for Pakistan WAPDA.

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1.0 GENERAL
Northern Pakistan is positioned along the north-west part of Indian plate which subducts beneath
Eurasian plate. The country has experiences various earthquakes in the past that resulted in high
rate of damages and killed thousands of people. Historically, the earthquakes have threatened
several areas of Northern Pakistan and left deeper impressions. Seismically active fault lines
(Figure-1) are located in this region that could make the population vulnerable to this disaster.
The Hindu Kush region generates regularly quite large earthquakes, occurring down to 300 km
depth, which are also felt in most parts of Pakistan. The direction of crustal stress in the Kashmir
is NE-SW, perpendicular to the line of plate collision and the MBT. In the Hindu Kush region,
the earthquake mechanism is generally thrust faulting occasionally normal faulting whereas in
the Kashmir, the earthquakes mainly show thrust faulting mechanism with a clear NE-SW
compression. Both the Karakoram and the Hindu Kush ranges are caused by the collision of
Indian and Eurasian plates.
Figure-1. Regional tectonic map showing the major fault systems in Northern Pakistan

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Northern and western sections of Pakistan are more sensitive to earthquake activity than the
other sections because they are surrounded by the micro plates of Afghanistan, Iran and India.
Main Central Thrust (MCT), Main Karakoram Thrust (MKT), Main Boundary Thrust (MBT)
and Main Mantle Thrust (MMT) are the major faults located in Northern Pakistan. The area also
includes two Syntaxial Bends, known as Nanga Parbat and Kashmir Hazara, where the rocks
strata are folded around this syntax and are subject to a 900 “rotation” from one side to the other
side (Figure-1). Seismic data indicates that movements along these faults and Syntaxial Bends
are the major causes of significant and destructive earthquakes.
Many of the earthquakes that occur on the MBT take place at shallower depths and are
associated with a shallow northward dipping subsurface extension of the MBT underlying the
MCT (the under-plating of the Eurasian plate). One section of the eastern Himalayan frontal
thrust was relatively quiet during the last many decades.
In the Gilgit Area of Gilgit-Baltistan (Western Himalayas), the seismic activity is associated with
the micro earthquakes and macro earthquakes of Mw ≥ 5.0, and largely coincides with the
surface trace of the Himalayan Main Central Thrust (MCT) rather than with the Himalayan Main
Boundary Thrust (MBT) which represents the structural boundary. Direction of the horizontal
compression has been deduced from the focal mechanism solutions. The mountains, notably
Hindu Kush, Pamir and Karakoram, are characterized by the deep and concentrated seismicity by
which significant seismic energy is discharged every year. The Hindu Kush and Pamir are
amongst the most active seismic regions of world. The Hindu Kush region generates regularly
quite large earthquakes, occurring down to 300 km depth, which are also felt in most of Pakistan.
The direction of crustal stress in the Kashmir is NE-SW, perpendicular to the line of plate
collision and the MBT. In the Hindu Kush region, the earthquake mechanism is generally thrust
faulting occasionally normal faulting whereas in the Kashmir, the earthquakes mainly show
thrust faulting mechanism with a clear NE-SW compression. Both the Karakoram and the Hindu
Kush ranges are caused by the Indian - Eurasian plate collision.
2.0 LOCATION OF GILGIT, NOMAL & NALTAR CITY
Gilgit, Nomal and Naltar city (Figure-2) is situated in the north-west portion of the Himalayan
Mountain System having extremely mountainous topography. The eastern portion of the area
consists of five well defined mountain ranges aligned in a north-westerly direction, slightly
curvilinear, and convex to the south which form a continuation of the general Himalaya Arc
towards Chitral. The mountain system swings to the south-west, resulting in an acute inflexion
convex to the north. The Hindu Kush and Karakoram Ranges of north Gilgit-Naltar conform to
this north-facing arcuate arrangement. The Kailas, Ladakh and Great Himalaya Ranges in the
south-west terminate along a zone approximating to the axis of same arc, where mountain trends
are poorly defined and asymmetrical.

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Figure-2 Location of Gilgit-Nomal &Naltar City
The highest peak in the region is Rakaposhi (7,788 meters) in the Kailas Range. Nanga Parbat
(8,114 meters) and Tirichmir (7,718 meters) are situated at short distance outside the region. At
high altitudes, the ranges are snow covered and glaciated. The Karakoram Range in Hunza
district is the most glaciated area in the region and contains Batura Glacier, the fourth largest in
the world. This Glacier is 59,546 meters long and terminates at 2,606 meters in the Hunza River
valley. The topography below the present snowline shows the effects of former glaciation.
Matterhorn-type peaks and sharp-crested aretes are separated by broad glacial tr6ughs, which
have a low gradient. The valley sides are characterized by cirques and minor hanging valleys.

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3.0 PRINCIPLES OF SEISMIC MICROZONATION
The practice of earthquake engineering comprises the identification and mitigation of seismic
hazards. Seismic Microzonation has typically been recognized as the most accepted tool in
seismic hazard assessment and risk evaluation and it is defined as the zonation with respect to
ground motion characteristics taking into account source and site conditions. Making
enhancements on the conventional microzonation maps and regional hazard maps, microzonation
of a region generates detailed maps that predict the hazard at much smaller scales.
Seismic microzonation is the generic name for subdividing a region into individual areas having
different potentials hazardous earthquake effects, defining their detailed seismic behavior for
engineering design and land-use planning.
The role of geological and geotechnical data is becoming very important in the seismic
microzonation in particular the planning of city urban infrastructure, which can recognize,
control and prevent geological hazards (Dai et al., 1994, 2001). The basis of seismic
microzonation is to model the rupture mechanism at the source of an earthquake, evaluate the
propagation of waves through the earth to the top of bed rock, determine the effect of local soil
profile and thus develop a hazard map indicating the vulnerability of the area to potential seismic
hazard. Seismic microzonation will also help in designing buried lifelines such as tunnels, water
and sewage lines, gas and oil lines, and power and communication lines.
The earthquake damage basically depends on three groups of factors: earthquake source and path
characteristics, local geological and geotechnical site conditions, structural design and
construction features. Seismic microzonation should address the assessment of the first two
groups of factors. In general terms, seismic microzonation is the process of estimating the
response of soil layers for earthquake excitations and thus the variation of earthquake
characteristics is represented on the ground surface. Seismic microzonation is the initial phase of
earthquake risk mitigation and requires multidisciplinary approach with major contributions from
geology, seismology and geotechnical engineering.
3.1 Scope of the study
The study of strong ground motion, earthquake hazard, and risk plays an important role in
modern seismology viz; it is of such great societal importance (e.g., Bilham et al., 2001; Bilham,
2006). Hazard analysis requires characterisation of the seismic sources that can be expected to
affect a selected place in terms of location, magnitude, and frequency of occurrence of
potentially damaging earthquakes.

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Using the hazard estimates produced by seismology, risk analysis yields deterministic or
probabilistic estimates of the expected losses of properties and lives from earthquakes, which in
turn is a convolution of the hazard estimates and vulnerabilities of structures, facilities, and
people distributed over the site. Seismic hazard also has a major impact on the earthquake-
resistant design of structures by providing justified estimates of hazard parameters, such as Peak
Ground Acceleration (PGA) or response spectrum amplitudes at different natural periods.
Traditionally, PGA has been a widely used hazard parameter, partly because it can so easily be
read from analogue accelerograms. However, PGA is often found not to be well-correlated with
the damage potential of ground motion, which has led to more frequent use of measures (such as
Peak Ground Velocity, PGV, or spectral acceleration, SA) that reflect also other wavelengths, or
frequencies. By taking into account the entire available databases on seismicity, tectonics,
geology and attenuation characteristics of the seismic waves in the area of interest, the seismic
hazard analysis is used to provide estimates of the site specific design ground motion at the site
of a structure.
The important result of present study is the preparation of seismic zoning maps for the
generalized applications. In this study historical data is used which is available only in intensity
scales for the ground motion, based on the description of observed damages. Intensity data is still
used as an important supplement to the instrumental recordings, not the least because it allows
for the use of historical observations.
3.2 Technical Approach
Design codes and construction details
The United States (U.S.) Army Corps of Engineers have issued a manual under Engineering and
Design (U.S. Army Corps of Engineers, 1999) in which several general guidelines are included.
While their approach is generally deterministic it contains key concepts that are applicable also
to the present study. The seismic assessment has several key steps:
• Establishment of earthquake design criteria. In the present case this means that the
definitions of Maximum Design Earthquake (MDE) and Operating Basis Earthquake
(OBE) are commonly understood.
• Development of ground motion corresponding to the MDE and OBE levels.
• Establishment of analysis procedures, i.e. procedures applied to reveal how the structure
responds to the specified seismic load.
• Development of structural models.
• Prediction of earthquake response of the structure.
• Interpretation and evaluation of the results.

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For the present study we will exclusively focus on the second bullet point above, except that we
refrain from using the terms MDE or OBE in the following, since these terms are relevant in
particular for sensitive structures such as Dams and Hydropower Projects. The background is
however a clear understanding of the MDE and OBE definitions:
• The Operating Basis Earthquake (OBE) is an earthquake or equivalent ground motion
that can reasonably be expected to occur within the service life of the project, that is,
with a 50% probability of exceedance during the service life. The associated
performance requirement is that the project functions with little or no damage, and
without interruption of function.
• The Maximum Design Earthquake (MDE) is the maximum earthquake or equivalent
level of ground motion for which the structure is designed or evaluated. The associated
performance requirement is that the project performs without catastrophic failure
although severe damage or loss may be tolerated.
While, in the following, ground motions for different annual exceedance probabilities are
provided, it is the responsibility of any contractor to associate the safety levels in terms of MDE
and OBE or in accordance with any other defined safety level, e.g., the national building
regulations.
As already noted, horizontal Peak Ground Acceleration (PGA) is the most commonly-used
measure of the ground motion in seismic hazard analyses for many purposes, and it is the
simplest way to characterize the damage potentials of an earthquake.
This study is entirely based on a probabilistic computation in which the expected ground motions
are evaluated for various levels of exceedance probability. Naturally, the various seismic
provisions and guidelines reflect first of all the seismicity level of the study area, where the
expectance for the future is based on the past experience. The most detailed seismic code
provisions come from regions like Japan, and the United States where strong earthquakes hit
frequently in regions with complex infrastructure. In such countries the seismic awareness is
very high due to the combination of past losses and economic strength that facilitates effective
counter measures.
The seismicity of Northern Pakistan is (as already noted) characterized by important historical
and recent major earthquakes, with a steadily increasing vulnerability of its northern and south-
western regions. Unfortunately, the seismic awareness of these regions is still low.
After the mega Kashmir-Hazara earthquake Mw = 7.6, of October 08, 2005, the Government of
Pakistan also implemented the “Building Code of Pakistan (Seismic Provision 2007). This
Building Code is in line with the International Building Codes in practice.

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Seismic design codes have the purpose of providing building guidelines for the reduction of both
property and life losses due to the seismic events. These building design codes define standards
for the seismic resistant design and construction of new building and for the retrofit of the
existing ones. Guidelines are developed based on sound theoretical and physical modeling and
on the observed damages caused by major earthquakes.
The lessons given by past earthquakes help to promote advances in the development of design
methods, the knowledge of materials performance and the enhancement of construction
practices. Basically, a seismic code contains specifications for the seismic hazard, including soil
and possible near-fault effects that should be used in seismic design of buildings in the
considered region, which in turn is based on a base shear load that the building should resist.
In Europe there has been a great effort in launching a set of Euro-codes (EC) which contains
complete guidelines for the construction industry including the seismic provisions (EC 8, 2004).
Euro-code 8 defines two goals of the anti-seismic design:
• The structure shall be designed to withstand the design seismic action without local or
general collapse.
• The structure shall be designed and constructed to withstand a seismic action (seismic
load) having a higher probability of occurrence than the design seismic action.
Modern codes, notably the 1997 Uniform Building Code (ICBO, 1997), EC-8, 2004, and the
Building Code of Pakistan (Seismic Provision 2007), are based on the specification of a base
shear that depends on the seismic hazard level of the site, site effects coming from the site
geology, near fault effects, weight, fundamental period, lateral forces, and the resisting system of
the building. In areas of high seismicity, sufficient ductile detailing to accommodate the inelastic
demand (Bachman and Bonneville, 2000) is needed.
The objective of this study is to provide the seismic actions at various annual exceedance
probability levels, in the areas of Gilgit, Naltar and Nomal. The building constructors/designers
must choose an appropriate risk level/exceedance probability level for the structure for which the
design ground motion is associated.
The selection of the appropriate risk level is essentially a question of the consequences of a
failure. The risk level is most often specified either as annual exceedance probability or as
exceedance probability during the expected lifetime of the structure (Figure-3). The discussion of
risk levels is supported through the following connection between return period TR and lifetime
T, where P is annual probability of exceedance.

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Figure 3 Relationship between return periods (inverse of annual exceedance probability),
Period of interest and desired probability of exceedance during the period of
Interest (according to Reiter, 1990).
If, for example, the expected lifetime of a structure is T = 200 years, and a 95% non exceedance
probability (5% exceedance probability, P = 0.05) is required, then this safety requirement
corresponds to a return period of TR = 3900 years, or an equivalent 3x10-4 annual exceedance
probability. The curves for various lifetime structures and the corresponding return periods are
shown in Figure-3.
4.0 METHODOLOGY OF PROBABILISTIC SEISMIC HAZARD
ANALYSIS
It is well known that uncertainties are essential in the definition of all elements that go into
seismic hazard analysis, in particular since the uncertainties often drive the results, and
increasingly so for low-exceedance probabilities. As might be anticipated this can sometimes
lead to difficult choices for decision makers. Rational solutions to dilemmas posed by
uncertainty can be based on the utilization of some form of probabilistic seismic hazard analysis.
In contrast to the typical deterministic analysis, which (in its simplest form) makes use of
discrete single-valued events or models to arrive at the required description of earthquakes
hazard, the probabilistic analysis allows the use of multivalued or continuous model parameters.

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As might be expected this can sometimes lead to difficult choices for the decision makers.
Utilization of PSHA provides us rational solutions to predicament posed by the uncertainties
involved. Contrary to the classic deterministic assessment, that (in its simplest form) uses the
discrete single-valued events or the models for arriving at the requisite description of
earthquakes hazard, the probabilistic assessment allows us to use the multi-valued or continuous
model parameters.
The use of PSHA consents to the explicit consideration of many factors such as uncertainties in
rate of recurrence, size and location of earthquakes as well as in variation of the characteristics of
ground motion with earthquake location and size while evaluating seismic hazards. PSHA offers
a frame where these just mentioned uncertainties can have their identification, quantification, and
combination in a cogent way to portray seismic hazard in a more comprehensive way.
Another advantage of PSHA is that it just estimates the likelihood regarding earthquake ground
motions or other damage measures occurring at the very site of interest. This allows us for a
more sophisticated integration of the seismic hazard and the seismic risk estimates; probabilistic
seismic hazard estimates can be extended to define the seismic risk at a certain site.
For this Project (study) PSHA of Gilgit, Nomal and Naltar is carried out.
Of most importance, the probability of different magnitude or intensity earthquakes occurring is
included in the analysis. Another advantage of probabilistic seismic hazard analysis is that it
results in an estimate of the likelihood of earthquake ground motions or other damage measures
occurring at the location of interest. This allows for a more sophisticated incorporation of
seismic hazard into seismic risk estimates; probabilistic seismic hazard estimates can be
expanded to define seismic risk.
The methodology used in most probabilistic seismic hazard analysis (PSHA) was first defined by
Cornell (1968). There are four basic steps for assessment of PSHA:
Step 1 is the definition of earthquake sources. Sources may range from small faults to
large seismotectonic provinces with uniform seismicity.
Step 2 is the definition of seismicity recurrence characteristic for the sources, where each
source is described by an earthquake probability distribution, or recurrence
relationship. A recurrence relationship indicates the chance of an earthquake of a
given size to occur anywhere inside the source during a specified period of time.
A maximum or upper bound earthquake is chosen for each source, which
represents the maximum event to be considered. Because these earthquakes are

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assumed to occur anywhere within the earthquake source, distances from all
possible location within that source to the site must be considered.
Step 3 is the estimation of the earthquake effects which is similar to the deterministic
procedure except that in the probabilistic analysis, the range of earthquake sizes
considered requires a family of earthquake attenuation or ground motion curves,
each relating to a ground motion parameter, such as peak acceleration, to distance
for an earthquake of a given size.
Step 4 is the determination of the hazard at the site, which is substantially dissimilar from
the procedure used in arriving at the deterministic hazard. In this case the effects
of all the earthquakes of different sizes occurring at different locations in different
earthquake sources at different probabilities of occurrence are integrated into one
curve that shows the probability of exceeding different levels of ground motion
level (such as peak acceleration) at the site during a specified period of time. With
some assumptions this can be written as:
where E(Z) is the expected number of exceedance of ground motion level z during
a specified time period t, αi is the mean rate of occurrence of earthquakes between
lower and upper bound magnitudes (mo. and mu), fi (m) is the probability density
distribution of magnitude within the source I, fi(r) is the probability density
distribution of epicenteral distance between the various locations within source I
and the site for which the hazard is being estimated, and P(Z>z | m,r) is the
probability that a given earthquake of magnitude m and epicenteral distance r will
exceed ground motion level z.
It is usually assumed when carrying out the probabilistic seismic hazard analysis that
earthquakes are Poisson-distributed and therefore have no memory; implying that each
earthquake occurs independently of any other earthquake. One of the most important of the
recent developments within PSHA has been in seismic source modeling. Originally, seismic
sources were crudely represented as line sources (Cornell, 1968) and later area zones, which
could be narrowed to represent the surface outcrop of faults as in McGuire’s (1976) computer
program EQRISK. An improved scheme, which included the effects of fault rupture, was
proposed by Der Kiureghian and Ang (1977), and in a modified form implemented by McGuire
(1978) in his fault modeling program FRISK, written as a supplement to his earlier and very
popular EQRISK area source program.

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While the standard practice for a long time was to present the results of seismic hazard analyses
in terms of a single best-estimate hazard curve, the growing awareness of the importance of
parametric variability and the trend to consult expert opinion in matters of scientific doubt, led
later to the formulation of Bayesian models of hazard analysis (Mortgat and Shah, 1979) which
seek to quantify uncertainty in parameter assignment in probabilistic terms.
4.1 Theoretical framework
The model for the occurrence of ground motions at a specific site in excess of a specified level is
assumed to be that of a Poisson process. This follows if the occurrence of earthquakes is a
Poisson process, and if the probability that any one event will produce site ground motions in
excess of a specified level is independent of the occurrence of other events. The probability that
a ground motion level is exceeded at a site in unit time is thus expressed as:
P (Z > z) = 1 - e − ν (Z)
Where
ν(z) is the mean number of events per unit time in which Z exceeds z.
According to the convention (McGuire, 1976) in probabilistic hazard analysis, the region around
a site is partitioned into polygons, which constitute a set of area sources. Basic differences in
seismicity and geology may exist between the zones; however, it is assumed that the seismicity
within each zone is sufficiently homogeneous to be treated uniformly in the computations. This
assumption applies even where non-seismological criteria have been used in the zone definition,
e.g., geological structures. With N seismic sources, and seismicity model parameters Sn for each
source n, the mean number of events pr. unit time in which ground motion level z is exceeded
can be written as:
where
and where λn = (Mi | Sn) is the mean number of events per unit time of magnitude Mi
(Mi ∈ [M min, M max]) in the source n with seismicity parameters Sn

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For a life time T of 50 years and a return period TR of 475 years (annual probability of
exceedance 0.211x10-2) the probability for Z exceeding z becomes 0.1, corresponding to 90%
probability that this size ground motion is not exceeded in 50 years. This is also illustrated in
Figure-3.
With several seismic sources, described through particular model parameters, the mean number
of events per unit time in which the ground motion level z is exceeded can be expressed
specifically, involving functions that model the inherent stochastic uncertainty in the frequency
and location of earthquakes, and in the attenuation of the seismic waves.
4.2 Recurrence Relationship and Seismicity Models
Earthquake recurrence may be described by the following general equation:
N (M) = f (M, t) (1)
Here, N (M) is number of earthquakes having magnitude not less than M while t is the time
period. In the simplest way, Equation (1) has been utilized as the Richter’s law and is given by
the following relation:
log N (M) = a – b M (2)
Above Equation has the assumption that all the earthquakes are spatially and temporally
independent having characteristics of Poisson’s model. Derivation of coefficients ‘a’ as well as
‘b’ can be done from seismic data and represent the characteristics of region of interest.
Coefficient ‘a’ is related to total number of earthquakes occurred in the source zone and depends
on its area, while coefficient ‘b’ represents the coefficient of proportionality between log N(M)
and the magnitude.
In seismic hazard analyses a modified and truncated version of this relation is used, involving an
engineering threshold magnitude Mim, a limiting upper bound magnitude Mmax for the source,
a slope parameter β = bxln(10) that describes the relation between the number of smaller and
larger earthquakes, and an activity rate parameter A=a(Mim) which describes the number of
events on the source with magnitude equal to or greater than Mim. See Figure-4 for two
recurrence models.

13
Figure-4 Earthquake recurrence functions. The red line indicates the truncated
cumulative Gutenberg-Richter relation, while the blue line indicates
the truncated characteristic recurrence model used in CRISIS.
The activity rate parameter is liable to vary substantially from one seismic source to another
while the b-value is expected to be regionally stable, with variations less than the uncertainty
limits. Faults, which may be separately included as seismic sources in addition to area sources,
are usually attributed their own b-values, which need to bear no immediate relation to the values
obtained from the regional recurrence statistics (Young’s and Coppersmith (1985).
5.0 BUILDING CODE OF PAKISTAN (BCP)
A building code is a set of rules that specify the standards for constructed objects such as
buildings and non-building structures. Buildings must conform to the code to obtain
planning/construction permission from concerned Authorities.
The main purpose of building codes is to protect public health, safety and general welfare as they
relate to the construction and occupancy of main buildings and structures. Seismic building
codes result in earthquake-resistant buildings, but not earthquake-proof buildings. Seismic codes
are intended to protect people inside buildings by preventing collapse and allowing for safe
evacuation. Structures built according to code should resist minor earthquakes undamaged, resist
moderate earthquakes without significant structural damage, and resist severe earthquakes
without collapse.

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After the destructive Mw = 7.6 Kashmir-Hazara earthquake an updated Building Code of
Pakistan (BOP), with Seismic Provision 2007, was implemented by the Government of Pakistan.
5.1 Soil Profile Types
Each site shall be assigned a soil profile type based on properly substantiated soil engineering
characteristics using the site categorization procedure. Building Code of Pakistan (BOP)
(Seismic Provision 2007) has defined the Soil Profile Types in following BOP Table-4.1.
6.0 ATTENUATION RELATIONSHIP
Earthquake is a natural phenomenon occurring inside the earth and then its energy travels
through earth structure in the form of seismic waves, which are reflected, refracted, diffracted,
amplified and attenuated. However, amplitude attenuation of waves is the most important
phenomenon.
Mostly peak ground acceleration (PGA) is the parameter which is referred in order to incorporate
the attenuation characteristics of a region. Earthquake resistant designing of structures and

15
facilities involves the estimation of ground shaking level which they will experience thereafter.
Since the level of shaking is most conveniently illustrated by ground motion parameters, thus the
methods to estimate the ground motion parameters are utilized.
Predictive relationships, which express a particular ground motion parameter in terms of the
quantities that affect it most strongly, are used for this purpose. Predictive relationships have a
significant role in conducting seismic hazard analyses which is used for the seismic design
(Kramer, 1996).
6.1 Predictive Relationships
Predictive relationships generally state ground motion parameters in terms of functions of
distance, magnitude and other variables (in some cases), such as,
Y=f (M,R,Pi) (3)
where
Y, M, R and Pi are ground motion parameter, magnitude of earthquake, source – site distance and
other parameters characterizing wave propagation path, local site conditions and/or earthquake
source, respectively. For example, peak values of the strong ground motion parameters exhibit
almost lognormal distribution (i.e., the logarithms of parameters are almost normally
distributed). Consequently, regression is generally carried out on logarithm of Y instead of Y
itself.
Predictive relationships have been built up by the regression analyses of the recorded or deduced
databases. Thus they keep on evolving and change/improve with time as further data become
available. Most predictive relationships are updated in the literature every three to five years or
shortly after the occurrence of large earthquakes in the well instrumented regions. Predictive
relationships are often region dependent and should be used in the region of similar conditions.
Moreover, definitions of important parameters used in these relations like M and R should be
taken into consideration while using them (Kramer, 1996).
Attenuation relationships show inverse proportionality of ground motion parameters like peak
acceleration and velocity with distance. A large number of useful attenuation relations for
different geographic and tectonic environments have been described in the literature and since
peak acceleration is considered to be the most frequently employed ground motion parameter,
most of these relationships involve peak ground acceleration.

16
All of these relationships are best suited to the conditions similar to those in the databases from
which they were developed. As additional strong motion data have become accessible,
attenuation relations have become more refined and sophisticated.
For the seismic hazard studies Northern Pakistan, different researchers have used different
attenuation relationships such as Abramson and Desolor (2008), Boor and Akison (2008),
Campbell and Bozorgnia (2008), Idriss (2008), Young (1971) and Next Generation Attenuation
Relations (NGAs) due to certain reasons by considering similar geo-tectonic and/or seismic
conditions as of the regions for which these relations were developed. These NGAs have been
developed with a vast data set and has been developed by the best researchers, who have worked
in the field of developing attenuation relationships for a long time. These relationships are
widely used by researchers these days especially in the absence of any attenuation relationship
which is region-specific. Most of the new SHA software has these relationships as in-built,
emphasizing on their usage and better understanding (EZ-RISK, Updated 2019).
The development of attenuation relationship is the area of present study which was previously
overlooked by the researchers due to many reasons. The most significant one is the scarcity or
absence of useful data.
In this study, Microseismic and Macroseismic data have mainly been collected from a number of
resources like Pakistan WAPDA Micro Seismic Monitoring System (MSMS) and International
Seismic Center (ISC),
Firstly attenuation relationship with the usage of Macroseismic data was developed as this data
was available at first instance and in relative abundance. Then the availability of acceleration
data invited to carry out regression on this data set. But as the data set was not a very strong one
especially in larger magnitude and closer distance ranges, there was still a prominent usage of
NGA and other suitable attenuation relations.
6.2 Attenuation Model
Empirical attenuation relation normally considered is of the type:
I(R) = a + bR + clogR (4)
Where, I(R) is intensity at a distance R from the epicenter of earthquake and a, b and c are
constants which are different for different region. The above relationship shows attenuation at
some distance away from the epicenter which becomes singular at R=0.
Making an assumption that at R=0, I(R) = Io, that is, at very short distances surrounding the
epicenter within the isoseismal of intensity Io, no attenuation is applied. To avoid such

17
singularity, following Chandra (1979), R is replaced by R+D where D is suitably chosen
constant. The relation thus can be written as:
I(R) – Io = bR + clog (1 +R/D) (5)
As the earthquake focus is always at some depth below the surface, the constant D is taken as
average depth of the events occurring in the region. It can safely be taken as 10 km for the entire
region.
Since in many cases it is difficult to have epicenteral Intensity Io, following Wang Suyan
methodology (Wang et al., 2000) it is converted to magnitude ‘M’ using Gutenberg and Richter
(1956) relation,
M = (2/3)Io + 1 (6)
Thus the modified relation can be written as
I(R) = 1.5(M-1) +bR +clog (1 +R/D) (7)
I(R) = -1.5 +1.5M + bR + c[log(R+D) – logD] (8)
I(R) = a +bR + c[log(R+D)] + dM (9)
or
I(R) = a +bM + cR + d[log(R+D)] (10)
Strong-motion (attenuation) models
There is evidence that the decay rate of ground motions is dependent on the magnitude of the
causative earthquake (e.g. Douglas, 2003), and the decay rate also changes systematically with
distance. Fourier spectra and response spectra moreover decay differently.
Geometrical spreading is dependent on wave type, where in general body waves spread
spherically and surface waves cylindrically, while an elastic attenuation is wavelength
(frequency) dependent. As hypocentral distance increases, the up going ray impinges at a
shallower angle on the interfaces, reflecting increasing amount of energy downwards, thereby
reducing the energy transmitted to the surface.

18
For moderate and large earthquakes the source can no longer be considered a point source and
therefore the size of the fault will mean the decay rate will be less than for smaller events, which
is essentially why, for large events, the distance to the causative fault (Joyner-Boore distance)
usually is used instead of epicenteral or hypocentral distance.
Assuming the occurrence of an event of magnitude Mi at a site-source distance of Rj, the
probability of exceedance of ground motion level Z needs to be defined. From studies of strong-
motion records, a lognormal distribution is found to be generally consistent with the data, where
the mean often have a simple form such as:
lnZ = c1 + c2 ⋅ Mi + c3 ⋅ ln Rj + c4 ⋅ Rj (11)
where
Z is the ground motion variable and c1 to c4 are empirically determined constants where c2
reflects magnitude scaling (often in itself magnitude dependent), c3 reflects geometrical
spreading and c4 reflects inelastic attenuation. Also found from the recorded data is an estimate
of the distribution variance.
One of the most important sources of uncertainty in PSHA is the variability or scatter in the
ground motion (attenuation) models, which is an aleatory uncertainty usually expressed through
a sigma (σ) value which is often of the order of 0.3 in natural logarithms, corresponding to about
0.7 in base 10 units. This uncertainty, which usually also is both magnitude and frequency
dependent, is mostly expressing a basic randomness in nature and therefore cannot be
significantly reduced with more data or knowledge. In PSHA we integrate over this uncertainty
which thereby is directly influencing (driving) the seismic hazard results.
6.3 Implementation
The earthquake criteria development performed for this study is, as explained in more detail
above, based on horizontal probabilistic seismic hazard analysis techniques designed to
incorporate uncertainties and to quantify the uncertainties in the final hazard characterizations
(confidence limits).
The procedure for identifying potential seismic sources in the Project region comprises:
• An evaluation of the tectonic history of the region in light of available geological
data and information.

19
• An evaluation of the historical and recent instrumental seismicity data in relation to
the project region, emphasizing that these data are the primary empirical basis for
conducting seismic hazard analyses. The present study is building on knowledge and
experience within the field of earthquake criteria development for numerous sites in
different tectonic environments, thereby ensuring results which are comparable on a
larger scale.
Geology
The general approach to this side of the seismic criteria development is to review relevant and
available geological information in order to locate and characterize active and potentially active
geological structures, i.e. faults and/or segments of faults which may represent a potential
seismic source that could influence the seismic hazard at the site. It should be noted however,
that the presence of a large fault is not always regarded as a potential earthquake source, since
faults are considered potentially active only if they have ruptured fairly recently (which on a
geological time scale could be as much as 10,000 years).
Seismology
A seismic hazard analysis should be based on both the geological and seismological history of
the region, including recent and historical seismicity, supplemented with paleo seismological
information if available (Kumar et al., 2006). The information called for here includes generally,
besides the usual earthquake catalogue, also information which can improve the understanding of
the geodynamics of the region, such as earthquake rupture processes, mode of faulting, stress
field, source mechanism, etc.
Seismotectonic interpretation
The geological and seismological information is used to define models for the potential
earthquake sources that could influence the hazard at the site. The main aspects of the source
characterization are:
i. modeling of area sources based on the geologic history of the region in
general and on earthquake occurrence statistics (historical and
contemporary seismicity catalogues) in particular, and

20
ii. modeling of fault-specific sources with three dimensional geometry, if
such detailed information is available. Note that fault modeling is rarely
included in regional hazard studies as the present.
The characterization of each seismic source will be as comprehensive as the data allows and will
specifically incorporate the uncertainties in each source characteristic. Maximum earthquake
magnitudes are assessed using a combination of physical methods, historical seismicity and
empirical evidence from geologically similar regions.
Strong Motion Attenuation Relationships
The present earthquake hazard study requires the availability of earthquake ground motion
models for peak ground acceleration and spectral acceleration, for the frequency range of
engineering interest. Available models include near field excitation as well as the attenuation
with distance, and the scaling with magnitude here is essentially developed for estimating the
effects of an earthquake which is not yet been observed in the region considered.
Strong-motion attenuation relationships are important in any seismic hazard model along with
seismic source characterization, and it is noteworthy here that the uncertainties in attenuation
often are among those which contribute the most to the final results. This is true for any area, and
in particular for the Himalaya region, where very few strong-motion observations exist in spite
of a high seismicity level.
Computational model
The actual seismic hazard computations for a specific site are based on integrated probabilistic
contribution to the ground motion by the fault-specific and area sources modified by the seismic
wave attenuation. The uncertainties of some of the input parameters are carried through the
computation.
Hazard results and design criteria
The relationship between a range of ground motion levels and the associated annual exceedance
probability (hazard curve) is established through median values for each frequency. An essential
element of the present earthquake hazard methodology is that seismic loading criteria may be
evaluated in terms of equal-probability (equal hazard) spectra. This means that each frequency is
evaluated independently, with its own uncertainty estimate.
The seismic loading criteria are specifically developed for bedrock outcrop (site with no soil).
Design response spectra for the required annual exceedance probabilities may then be developed

21
based on the PGA values, and in certain cases accompanied with sets of real time histories
(earthquake recordings), appropriately scaled to match the spectra. Thelatter is done only when
specific advanced design analysis is conducted.
7.0 SEISMOTECTONIC SETTING OF NORTHERN PAKISTAN
Plate tectonics has been very successful in providing a rational framework to explain large scale
geological and tectonic features, both on the boundaries between but also within the tectonic
plates. Seismicity and fault plane solutions clearly outline the fault zones and relative motion of
the tectonic plates, and new GPS measurements have opened for significant new insights into the
dynamics of plate motions. Plate tectonics theory also successfully explains the Himalayan
mountain ranges as a result of the collision of the Indian plate with the Eurasian plate, as shown
in Figure-5.
Figure-5. Indian Plate Colliding with Eurasian Plate.
The Indian subcontinent has been colliding with the Eurasian subcontinent over the last 30-40
million years (Aitchinson et al., 2007). During this period, continental lithosphere longer than
2000 km has been shortened into the massive mountain ranges and elevated plateaus of central
Asia (e.g., Molnar and Topponier, 1975; Bollinger et al., 2004). (Figure-6)

22
Figure-6. Major tectonics in Pakistan (courtesy: Geological Survey of Pakistan).
The earthquake activity as shown in an overview map in Figure-7 clearly demonstrates how the
earthquakes (seismicity) concentrate along the plate margins. Even when the details about the
map (time period, sources, magnitude type etc.) are not available it shows clearly the regional
earthquake distribution.
More detail observations indicates collision point of Indian and Eurasian plates. Nearly 50 to 55
million year ago the two continental plates collided at this junction. The tremendous amount of
pressure created caused the Earth crust to buckle, producing large horizontal and vertical

23
displacement and also producing these mountains of the Karakorum. The Indian plate is still
moving towards north into the Eurasian landmass at about five centimeters a year causing the
mountains to raise about seven millimeters annually.
Even though the Himalayan region is huge and contains large parts that are remote and sparsely
populated we still have some overview of the seismicity there for the last 500 years, even with
indications of an earthquake deficit at present (e.g., Ambraseys and Bilham, 2003; Bilham and
Ambraseys, 2005; Feldl and Bilham, 2006). As a result of the continent-to-continent collision in
the Himalayas, the highest mountains in the world have been created (Figure-5), still being
uplifted more rapidly than any other mountain chain.
Some of the greater mountain structures resulting from the collision can be summarized as
follows:
• The Himalayas have been formed in the central part.
• The Arakan-Yoma Mountains of Burma.
• The Naga Hills of Assam towards the east.
• To the west, the Baluchistan arc manifested by the Kirther and Sulaiman ranges
delineate the continent-continent collision zone.
• The rising mountain ranges of the Tien-Shan Mountains in central Asia.
• The Karakoram Mountains in Pakistan.
• The Hindu Kush Mountains formed at the junction of the Baluchistan arc.
• The Karakorum Mountains and the Pamir ranges (Desio, 1965).
Figure-7 shows the regional seismicity and the fault in the Arabian Sea which has generated
earthquakes including the 1945 earthquake which generated a tsunami.

24
Figure-7. The regional seismicity of Southern Asia (above magnitude 3.0) according to
the British Geological Survey (BGS).
According to the Figure-5, the mountains, notably Hindukush, Pamir and Karakorum, are
characterized by deep and concentrated seismicity through which significant seismic energy is
released every year. Seismically, Hindu Kush and Pamir is one of the most active regions in the
world (Figure-8). The Himalayas and the Baluchistan Arc are the southernmost frontal parts of
this collision zone which extends northward through Afghanistan and Tibet into China and
Central Asia.
The NW-SE trending mountains of Kashmir, which form the western part of the Himalaya Arc,
bend sharply to the south near Nanga Parbat (Meltzer et al., 2001) forming the western
Himalayan syntaxes (often called the Kashmir-Hazara syntaxes).

25
Figure-8. Seismotectonic Fault System of Northern Pakistan.

26
8.0 GEOLOGY OF GILGIT, NOMAL & NALTAR REGION
The rocks mostly exposed in the Gilgit, Nomal and Naltar Region (area 300 km radial distance
around Gilgit), are mainly basalts, andesite sheets, and dominant volcanic and igneous rocks and
in some places there are Meta sedimentary rocks (Figure-9).
Figure-9. Geology of Gilgit-Naltar Region (area 300 km radial distance around Gilgit).

27
The rocks are highly sheared and fractured. The region is still rapidly uplifting and being
intensely denudated (Burbank et al., 1996). Denudational processes include frost shattering
(Hewitt, 1968c; Goudie et al., 1984), chemical weathering by salt crystal growth (Goudie, 1984.,
Walley et al., 1984), glacial erosion, fluvial incision and mass movement. All these processes are
responsible to immense quantities of fine sediment, which has the potential to be deposited
within lacustrine environments.
8.1 Geology of Gilgit, Nomal & Naltar City
Gilgit, Nomal and Naltar City are home to three mountain ranges: the Himalayas, the
Karakoram, and the Hindu Kush. Most elevations in the province are at least 1,500 m above sea
level, with more than half the area above 4,500 m. Three of the world’s highest peaks, K2;
Nanga Parbat; and Rakaposhi, are located in this district (Figure-10).
Figure-10. Junction of Karakoram, Hindukush and Himalaya Mountain Ranges near Gilgit.

28
Gilgit is located at the foothills of the Karakoram Mountains, roughly at the junction between the
three mountain ranges. The average altitude of the city is 1,500 meters. The general elevation of
the city is around 1,500 meters (m) and it is a semi-arid region that receives little annual
precipitation. Gilgit is surrounded by steep mountains with little or no vegetative cover. It lies at
the intersection of the Gilgit and Hunza Rivers at a place locally known as Duo Pani. It is
surrounded by peaks that range from 1,600 m to 2,000 m on either side of the valley. The
topography effectively cuts off the entire province from Pakistan’s mainland and, therefore,
creates geographical barriers that affect economic and administrative processes in GB.
The area is deeply dissected by streams fed by melting ice and snow. The drainage has a
dendritic pattern and constitutes portion of the Indus River System. The Indus River crosses the
south-eastern section of Gilgit-Naltar district and its major tributary here is the Gilgit River
draining south from the Hindukush and Karakoram Ranges.
Figure-11. Blue Lake in Naltar Formed by Landsliding/Rocksliding.
The orientation of the Gilgit, Nomal and Naltar valley system is strongly controlled by the
tectonics of the area. Most of the lakes situated in the mountains are glacier dammed lakes, or
lakes formed from the blockage by debris flows, rock fall and by land sliding. The Trans-
Himalayan Mountains are the result of the collision of the Asian and Indian continental plates.
The region contains highest snow peaks, glaciers, lakes and rivers with highest sediment loads in
the world, i.e. the Indus, Gilgit and Hunza rivers. Many types of lakes have existed and still exist
in the high mountains of Karakoram. However, there is no tectonically formed lake (Figure-11).

29
The level of the Gilgit and Hunza Rivers at the point of' confluence is 1,387 meters and their
average gradient between 2438 meters and their junction is 11 to 12 meters per kilometer. The
larger rivers generally occupy narrow gorges. The extreme relief resulting from deep dissection
is the outstanding topographical feature. Rakaposhi, for example, is 5,959 meters higher than the
Hunza River at Maiun, situated only 14.5 kilometers distance, the mean fall being 662 meters per
kilometers. In some places where the valleys are wider, and at the junctions with major
tributaries, extensive alluvial terraces and fans are formed marginal to the rivers.
The Gilgit Formation of Khan et al. (1994) includes paragneisses and schists, commonly
interstratified at regular intervals. They are metapsammites and metapelites and trend in NWSE
direction with steep dip either towards south or north, and attain an approximate thickness of I
km. These rocks are exposed in the vicinity of Gilgit, between Jaglot and Gilgit along the
Karakoram Highway (KKH), Jutial Gah, Kar Gah and Sai Nala. Other rocks comprising the
Gilgit Formation are the amphibolite and calc-silicate rocks (Figure-12).
Figure-12. Generalized Geological Map of Gilgit-Nomal and Naltar.
Taken from Searle & Dr. Asif Khan Geological Map of North Pakistan 2014.

30
The Hindukush range is located in the west of Gilgit-Naltar district, bordering with Chitral in the
west, and Afghanistan to north. Towards south it borders with district Diamer. The Northern
Areas has got extensive inland water resources comprising rivers and glacier lakes with varying
potential for the development of inland fisheries on aquaculture in the region. The lakes in the
Hindukush range are mostly glacier lakes mainly formed as a result of the blockage of the main
river by advancing tributary glaciers. The topographic setting is at the current stage of glaciations
in the Hindukush region favorable for the formation of this dam type. Tributary glaciers with
catchments areas of over 7000 m in height descend down to low altitudes below 3000 m into the
glacier-free trunk valleys and block temporarily the main river.
The section from Gilgit-to Sor Laspur is exclusive of sediments of the Darkot Group and the
Ladakh Granodiorite between Hopar and Roshanp has been included in the Greenstone
Complexo From Gilgit to Henzal Kain the rocks are quartzite, grey schists, banded cherts with
epidotised pillow lava to Westwards, the succession shows little variation except a gradual
increase in the quantity of basic lavas. From Burbur to Hopar, basalts, tuffs, quartzite and
agglomerates, which contain rounded pieces of marble are the main rock types (Figure-12).
Along the Jacot Village the rocks observed are meta-basaltic rock. More detail observations
indicates volcanic rock (basaltic rock), which is of dark colored, fine grain igneous rock. It is
most commonly form as an intrusive and extrusive such as lava flow. At some places also
observed is pillow basalt on right side of the road. Pillow basalt was developed at the time of
extension in that area because pillow basalt erupts underwater or flows into the sea and form
pillow like structure. Here also observed are green schist facies, the green color is due to the
mineral chlorite and epidote mineral it is medium pressure and temperature facies. Greenish
color result because of very low grade of metamorphism.
Wadia (1938) has shown that volcanic rooks-referred to as “Punjal Traps" similar in lithology to
those described in his report, occur in north-west Kashmir and Hazara Districts They are
regarded as Upper Carboniferous to Upper Triassic age in some places whereas in other places
they are not recorded in systems younger than Permiano. At ChaIt lavas are found in the upper
portion of the Darkot Group and it is suggested that these volcanic rocks marked the introduction
of a period of canicity, which led to the formation of the Greenstone Complex.
Along the Thelechi area the rocks observed are Schist/Phyllite Detail. Phyllite and in some
places schist is present. Grains of this are not seen, because it was fine grain. It is basically
sedimentary rock and they metamorphose and convert to phyllite/schist. It is the part of Jaglot
group. Jaglot group have different type of meta sediment. It has turbiditic sequence like Phyllite,
Shist-Phylite. In Kohistan Island Arc sediments were deposit in Back arc and after then because
of collision they metamorphosed. In this area igneous intrusion occurs i.e. Kohistan batholith
intrudes. Here rocks are of the Thelitic formation, which is a part of Jaglot group.

31
9.0 FAULT SYSTEM OF NORTHERN PAKISTAN
It has been established that the major faults of Pakistan appear to be seismically quiet except at
the times of large earthquakes (e.g. Nakata et al., 1991). It seems that this silence (or seismic
gap) is at least true for the Himalayas. It represents a problem while conducting seismic hazard
evaluation as we can find a seismic gap in an area and it may be found inactive for larger time
periods than the monitoring record. Also, while a thrust regime clearly dominates in several
places of the study area, it is often difficult or impossible to associate specific seismic activity
with specific fault traces, and this leads to the conclusion that many faults may be blind.
In the Kashmir region the important Hazara-Kashmir Syntax (HKS) is found, which was formed
due to the change in the Himalayan thrust interface direction from NE in Kashmir to the NW
along the Indus. The Punjal thrust as well as the MBT (Main Boundary Thrust) are folded around
this syntax and are subject to a 900 “rotation” from one side to the other side (Figure-13). Active
Jhelum fault truncates the Punjal thrust, MBT and Kashmir thrust (Baig and Lawrence, 1987).
Beside other faults in the region, the Jhelum fault acts as an active left-lateral oblique reverse
fault. General seismicity pattern of the Jhelum-Ambore zone is low activity of regular
earthquakes with magnitudes ≤ 4.0. The historical and the instrumental seismic data from this
region show no earthquake with a size exceeding magnitude Mw 6.8.
Figure-13. Seismotectonic Model of Northern Pakistan

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9.1 Kohistan Faults
The boundaries of major Lithological units within the Kohistan Island Arc (KIA) area are known
to be faulted based on geological mapping. The average rupture length of potential earthquake
faults in the Kohistan province is considered to be in the range of 100 km, based on examination
of map trace lengths and field observations of features during geotectonic investigations. The
Kohistan Oceanic Arc is bounded in the north by the Main Karakoram Thrust (MKT) and in the
south by the Main Mantle Thrust (MMT) (Figure-13). Along the MKT the region is sutured to
the Asiatic mass/Asian Plate, including the Eurasian Continent and Karakoram micro-continental
blocks. The territory of Kohistan covers about 36000 km2.
The igneous rocks of this complex display several phases of tectonic deformation during which a
penetrative tectonic fabric was generated. During this tcto genesis the basic rocks were deformed
into a series of recumbent south-verging isoclinal anticlines separated by tight narrow synclines.
The sub-horizontal fold axis and the northerly dipping regional tectonic layering mostly trend
roughly east west.
9.2 The Main Karakoram Thrust (MKT)
The Main Karakoram Thrust or the northern mega shear represents the collision zone of the
southern margin of the Eurasian plate in Asia and extends into the Baltistan area through
Hashupa and Machie in the Shigar and Shyok valleys, respectively. MKT is a high angle,
seismically active thrust with a large number of earthquakes of low to medium intensity (Seismic
Risk Map of Northern Pakistan, 1988, PGS). It is considered that rupture during earthquake on
the MKT could take place over a large area and could involve a relatively long portion of the
fault system. This equates to known ruptures on smaller boundary structures elsewhere in the
Himalaya and the fact that the fault zone is comparatively straight over significant distances.
9.3 The Main Mantle Thrust (MMT)
The Main Mantle Thrust or the southern mega shear is a north-ward dipping regional thrust
which detaches the Indian plate from the Kohistan Island Arc. It spans an area of approximately
400 sq. km through the Diamer, Kohistan, Swat, Dir and Bajaur with a total length of 420 miles.
Its extension is from Khar (Bajaur Agency) in west to Narran in the east. Shortest distances from
Islamabad and Peshawar are 87 and 46 miles, respectively. The structure is inclined at a steep
angle near the surface but the dip is thought to decrease with depth, as interpreted for other
thrusts in the region. As such, it is possible that this fault may pass under the site at some depth.
A branch of this fault got activated after the Pattan earthquake (28.12.1974) and some of the
aftershocks were associated along that branch.

33
Auxiliary structures associated with MMT include several imbricate thrusts and shears sub
parallel to the main structure, including the Kamila Shear Zone (KSZ) and other features in the
hanging wall of the MMT. These structures come closer together east of Chillas, and merge
along the flanks of the Nanga Parbat-Haramosh Massif (NPHM). It is considered that rupture on
MMT would be limited to comparatively short segments of the systems of the faults, shears, and
sutures that make up this major crustal feature. This assumption is supported out by geological
field evidences and the fact that the trace of the feature is remarkably sinuous.
8.4 The Main Boundary Thrust (MBT)
The Main Boundary Thrust is a distinct and important tectonic feature along the entire
Himalayan Belt. The MBT loops around the Hazara syntaxial zone. It represents the major zone
of recent deformation and the largest earthquakes. The MBT stretches from the Afghan border,
and can be traced nearly continuously to the Assam through Eastern India. It is the single most
potent earthquake source in the Himalayas. Islamabad-Rawalpindi area is located at a close
distance south of the western limb of the MBT. MBT and MMT are mostly considered to have
different segments while calculating the associated seismic hazard (Figure-13).
A number of large to major earthquakes have occurred along the Himalayan Arc east of the
Hazara-Kashmir Syntaxis during the last two centuries, which places it amongst the most active
regions of the world. Much of the seismicity recorded during the last century is attributed to
surface and subsurface extensions of the MBT and other associated thrusts.
10.0 SEISMOTECTONIC OF GILGIT BILTISTAN
According to “Seismotectonic Map of Pakistan”, a sizeable part of Gilgit-Baltistan belongs to a
major earthquake zone with recent past earthquakes with magnitudes of M ≥ 6.5 of the Richter
scale (Pakistan WAPDA). Several fault-lines are believed to be passing through different parts of
Gilgit-Baltistan. The Main Karakorum Thrust, originating in the Himalayan Arc is believed to
extend up to the Pamir mountain range. Several off-shoots of the MKT are also passing through
different valleys and villages of Gilgit-Baltistan. The Karakoram Highway (KKH), a part of the
China– Pakistan Economic Corridor (CPEC), connects Gilgit-Baltistan with Western China. It
passes through rapidly rising mountain ranges of the Himalaya, Karakoram and Hindu Kush
forming the junction between the Indian and Eurasian plates.
10.1 Seismotectonic of Gilgit, Nomal & Naltar Region
The seismic map of Pakistan indicates that Gilgit, Nomal and Naltar Region (area within 300 km
radial distance off Gilgit) lies in a very active seismic zone and the seismic factor in this zone has
been evaluated as Zone-III (Figure-14) of noticeable seismic danger with acceleration values of
0.24 to 0.32 g. and to the immediate north and north-west lies the Zone-IV of significant seismic
danger with acceleration values of ≥ 0.32 g.

34
Figure-14. Seismic Zoning Map of Pakistan.
The root cause of most seismic events can be related to tectonic processes in the upper portions
of the earth crust. The earth crust is divided into several plates. Buildup of strain/strain within
these plates or margins is due to the deformations taking place as results of movements along or
relative to the interfaces or margins of the plates. The Northern parts of Pakistan are near to the
collisional boundaries of Eurasian and Indian plates margins and therefore seismically very
active (Figure-15).

35
Figure-15 Seismotectonic Map of Gilgit-Naltar Region and Locations of Major Earthquakes.
Along the Gilgit-Naltar Region the seismicity largely coincides with the surface trace of the
Himalayan Main Central Thrust (MCT), Main Karakoram Thrust (MKT) and Main Mantle
Thrust (MMT). The Region is characterized by fractured and weathered rock masses, diverse
lithologies (igneous, metamorphic, and sedimentary), high seismicity, deep gorges, high relief,
arid to monsoon climate and locally high rates of tectonic activity.

36
In this Region the Raikhot fault zone and associated structures exhibit remarkable neotectonic
features including over-thrusting of Nanga Parbat Haramosh Massif (NPHM) gneisses over the
MMT and Pleistocene tillites, fault scrapes and geothermal activity.
Some major earthquakes that caused loss of life and destruction in the Gilgit-Naltar Region,
during the recent past are: the 1974 Pattan earthquake of mb 6.0, the two Bunji earthquakes of
mb 5.3 and mb 6.0 in 2002, the Astor mb 6.1 earthquake of January 2003, the 2004 Batgram
earthquakes of mb 5.3 and 5.5, and the recent Kashmir-Hazara earthquake Mw = 7.6 of October
8, 2005, have caused considerable damage and loss of life in Northern Pakistan and also some
structural collapse in Gilgit-Naltar Region. The most recent New Mirpur earthquake Mw 5.8 of
September 2019, was also felt in the Region, but without any structural damage or loss of life.
It is believed that in August 1871 a shallow focused earthquake Mw = 6.3 with epicenter in
Gilgit city was felt widely (Jacob 1979). It’s computed Intensity at Gilgit city is VIII and at
Naltar valley is VII on Modified Mercalli Scale (MMS). However, later on till date, no
earthquake with Mw ≥ 6.0 has been located from Gilgit-Naltar area.
11.0 DEVELOPMENT OF EARTHQUAKE DATA CATALOGUE
Microzonation of Gilgit-Naltar Project mainly depends on the Comprehensive Seismic Data
Catalogue. Any further processing, analysis and achievement of results is done from the data
catalogue. Therefore this catalogue is developed with utmost care.
Several attempts are being made by various institutions in the world to provide the earthquake
data which is easily accessible through organized databases. The main data bases for the
earthquake information in this study were:
. For the period of instrumental recording, International Seismological Centre (ISC)
hypocenter database was generally accepted a standard source for earthquake
parameters. ISC publishes revised event epicenteral locations around 12 months
after their occurrence. Instrumental data was collected from the ISC hypocenter
database (ISC, 2019).
. The United States Geological Survey (USGS) collects, monitors and analyzes the
earthquake data which presents scientific understanding about the natural resource
issues, condition and the problems. Instrumental data was collected from the
USGS hypocenter database (USGS, 2019).

37
. ANSS composite catalogue is a worldwide earthquake catalogue which is created
by the merging of master earthquake catalogues from the contributing ANSS
institutions while removing duplicate solutions of the same seismic event. ANSS
catalogues presently consist of earthquake hypocenters, date and magnitudes.
Instrumental data was collected from the ANSS hypocenter database.
. Pakistan WAPDA MSMS is operating a network of 29 seismic stations in
Northern Pakistan. Therefore very important seismic data was also collected from
the 2019 database of Pakistan WAPDA.
. National Engineering Services Pakistan (NESPAK) has also made quite a
composite earthquake catalogue up to Year 2018.. NESPAK instrumental data
was also collected.
The data in the spatial window was selected region-wise (on the basis of latitude and longitude
ranges) and desired catalogue was collected from the data sources.
11.1 Catalogue Compilation
CompiCat software package was utilized for the compilation of the instrumental seismic data
catalogue. This software package is a C++ code which supports the Gregorian calendar (adopted
by England from September 14, 1752). CompiCat was quite useful for:
. Importing the catalogues of diverse formats and converting them into the standard one.
. Exporting the catalogues into commonly used formats. Editing and compilation of the
earthquake catalogues (including checks for errors and disorder).
. Conversion of different magnitude scales into the common one.
. Duplicate records identification and their removal from the catalogue.
. Merging of the catalogues into a single one.
. Section of the sub-catalogue.
. Comparison of the catalogues.
. Calculation and the visualization of spectrograms and histograms for a given catalogue
etc. Catalogue compilation was done in this study by carrying out the following basic
actions (Saeed, 2009):

38
11.2 Historical Seismic Data Catalogue
The information on intensity or magnitude and frequency of earthquakes is necessary for proper
assessment of the seismicity and seismic hazard of a region. For this purpose a comprehensive
and an accurate data base of the past earthquakes is required. Without this, correct determination
of return periods is difficult. A good earthquake data base is imperative for understanding the
seismotectonics of a region.
In Pakistan, the present seismic hazard estimates are based on the limited historical data as the
information on earthquake prior to 1800 C.E. (Common or Catholic Era, just as A.D.) is not
abundantly available. There may be several reasons for this insufficient information on
earthquakes in Pakistan. The most important one is that the historians have primarily focused
their attention on political and social history of the Sub-continent. Earthquakes, if they were not
devastating, rarely found a mention in the accounts of history. On the other hand, there had been
no serious attempt to scan primary sources of history for this important purpose. The task
becomes complicated because most of the sources of history are not in the modern and current
languages and scripts.
The present work mainly concentrated on the past historical record as far back in date as
possible. Primary sources of history for this period were available in the form of writings of
court historians, travelogues, old catalogues and other documents. Historical earthquake
catalogue serves both as a smart tool to understand the long-term seismic activity as well as an
unswerving input for the seismic hazard evaluation. This task was accomplished by refining the
catalogue of National Engineering Services of Pakistan (NESPAK) which was compiled for the
Building Code of Pakistan-Seismic Provisions 2007.
Quittmeyer and Jacob (1979) gave the historical account of earthquakes of Pakistan,
Afghanistan, North-western India and the South-eastern Iran. His catalogue included earthquakes
from 25 C.E. to 1972 C.E.
11.3 Working File
As the data was retrieved from the sources, a working file of the data has been generated.
The resulting historical catalogue presented in Appendix-A is the most comprehensive and
updated catalogue for Gilgit, Nomal Valley and Naltar Valley. From Appendix-A, it reflects that
northern Pakistan as a whole has remained a house of damaging earthquakes. Taxila (25 A.D.)
event is probably the most conspicuous one that changed style of building-construction out-
rightly in this region.

39
11.4 Instrumental Seismic Data Catalogue
Earthquake catalogues have been one of the vital products of seismology. Homogeneous and
complete earthquake catalogues are compiled for different purposes and specific to certain areas
of seismology such as seismic risk, earthquake physics and hazard analysis (Kagan, 2003;
Woessner and Wiemer, 2005). Catalogue accuracy is one of the most important considerations
while quantifying any earthquake catalogue because of its influence on the obtained results
(Kagan, 2003). Accurate source parameters and fatality estimates is a task which is simple in
theory but a really challenging one in practice.
Earthquake catalogues as well as reports and also the online databases are the sources to collect
the necessary information. Some catalogues offer high quality hypocenters, while others enclose
lower quality hypocenters through carefully researched damage reports etc. (Allen, 2009).
Improvements in seismic observation and catalogue reporting can be done by examining the
catalogue properties (Kagan, 2003). For earlier centuries, description of Macro-seismic effect
only was relied upon, but for Gilgit Naltar Region, the data becomes scarcer if we go a few
hundred years back in time.
For the present phase of the study a composite list of seismic events that occurred in the Project
region has been prepared. It is based upon earthquakes reported by International Seismological
Center (ISC), United States Geological Survey (USGS), and Micro Seismic Monitoring System
(MSMS) of WAPDA at Tarbela, Micro Seismic Observatory of WAPDA at Mangla, Micro
Seismic Study Program of PAEC and Pakistan Meteorological Department.
From this composite list, events bounded within an area between latitudes 34° to 36° and
longitudes 73° to 75° have been selected for the seismic studies of Peshawar BRT Project. The
area confined by those latitudes and longitudes is mentioned as Peshawar Region in this
report/studies. This composite earthquake catalogue for the Gilgit-Naltar Region is presented in
Appendix-B.
This catalogue comprises over 17000 seismic events of different magnitudes. The above
mentioned reporting agencies have reported a variety of magnitudes viz. Body-wave magnitude
(mb), Surface-wave magnitude (MS), Richter/Local magnitude (ML).
Since attenuation relationships are based on magnitude of given type, a single type must be
selected. For data to be used in seismic hazard analysis, all the magnitudes were therefore
converted to moment magnitude (MW) by the following equations. Conversion from MS and mb
to MW was achieved through latest equation suggested by Scordilis (2006):

40
MW = 0.67 MS + 2.07 for 3.0< MS < 6.1 (12)
MW = 0.99 MS + 0.08 for 6.2< MS < 8.2 (13)
MW = 0.85 mb + 1.03 for 3.5< mb < 6.2 (14)
For ML up to 5.7, the value of ML was taken equal to MW as suggested by Iris (1985) and
supported by operators of local networks in Pakistan. Conversion of ML to MW beyond
magnitude 5.7 was done by using the following equations suggested by Ambraseys and Bommer
(1990) and Ambraseys and Bilham (2003):
The compiled composite list of earthquakes in the form of instrumental seismic data catalogue of
the area was used as the database for the determination of recurrence relationship. Instead of
different magnitude values in the updated composite seismic data catalogue, a single type of
magnitude, moment magnitude (Mw) was used from the catalogue as all the magnitudes had
been converted through incorporating latest equations suggested by different researchers
(Scordilis, 2006; Idriss, 1985; Ambraseys and Bommer, 1990; Ambraseys and Bilham 2003).
12.0 ANALYSIS OF SEISMIC DATA
The seismic events of Gilgit, Nomal and Naltar (GNN) Region (area within 300 km radial
distance off Gilgit) observed during last hundred years and presented in Appendix-B is plotted
on Figure-15 through the help of Generic Management Tool (GMT) Software.
The GNN Region mostly shows E-W trending folds and faults. The deformation within this zone
is primarily the result of thrusting and of deep crustal decollement processes associated within
the collision of the plates. The map indicates that most of the seismic activity is aligned along
known faults that are controlling the seismotectonic of GNN Region. However, in the seismic
activity map, many of the located seismic events may not be associated to the surface tectonic
faults and may be attributed to features present at shallow depths.
Within some areas of the seismic activity map the observed seismicity is relatively low and do
not consist of higher magnitude events. This implies that the regional tectonic features in the
Region are seismically active at moderate to high level magnitudes, due to stresses developed as
a result of collision of the tectonic plates.

41
Figure-16. Seismicity Within Gilgit-Naltar Region (300 km radial distance off Gilgit)
From 1828 through 2018.
This map (Figure-16) shows the presence of seismic activity in east, north and south of the
Project area which could be associated with faults present in this region. The cluster of seismicity
in the north-west off Gilgit, Nomal and Naltar area (GNN), is related to the active Hindukush
Seismic Zone (HSZ) and Main Karakoram Thrust (MKT). The cluster of seismicity east of GNN
is related to earthquake activity along the Indus Kohistan Seismic Zone. This cluster of seismic
events also includes the aftershocks of mega Kashmir Hazara earthquake of October 08, 2005.

42
This plot shows the presence of seismic activity in east, north and south of the Project area which
could be associated with faults present in this region. The cluster of seismicity in the north-west
off GNN is related to the active Hindukush Seismic Zone (HSZ) and Main Karakoram Thrust
(MKT). The cluster of seismicity east of GNN is related to earthquake activity along the Indus
Kohistan Seismic Zone. This cluster of seismic events also includes the aftershocks of mega
Kashmir Hazara earthquake of October 08, 2005.
It is therefore assumed that the GNN Region is seismically active up to shallow depths. In the
south of the GNN area, the seismic activity is low to moderate and related to the seismically
active faults present in the area.
13.0 PSHA OF GILGIT, NOMAL & NALTAR (GNN)
Probabilistic Seismic Hazard Analysis (PSHA) of Gilgit, Nomal and Naltar (GNN) area has been
carried out incorporating the basic methodology presented in the preceding section and utilizing
the latest state of the art software EZ-FRISK (2019). The program calculates the earthquake
hazard at a site under certain assumptions specified by the user. These assumptions involve
identifying where earthquakes will occur, what their characteristics will be, and what will be the
ground motions generated. These capabilities allow a wide range of seismic hazard problems to
be solved, with straightforward specification of input. Its easily allows in identifying the critical
inputs and decisions affecting seismic hazard evaluations.
13.1 Identification and Characterization of Seismic Sources
This first step regarding identification as well as characterization of earthquake sources entails
that all seismic sources which can generate sufficient ground motion at a particular site are at
first instance identified as well as characterized. This source characterization contains the
definition of geometry of each source, each source zone earthquake potential etc. with certain
degrees of uncertainties.
13.2 Recurrence Relationship and Seismicity Models
Earthquake recurrence may be described by the following general equation:
N (M) = f (M, t) (15)

43
Here, N (M) is number of earthquakes having magnitude not less than M while t is the time
period. In the simplest way, Equation (7-1) has been utilized as the Richter’s law and is given by
the following relation:
Log N (M) = a – b M (16)
Above Equation has the assumption that all the earthquakes are spatially and temporally
independent having characteristics of Poisson’s model. Derivation of coefficients ‘a’ as well as
‘b’ can be done from seismic data and represent the characteristics of region of interest.
Coefficient ‘a’ is related to total number of earthquakes occurred in the source zone and depends
on its area, while coefficient ‘b’ represents the coefficient of proportionality between log N(M)
and the magnitude.
14.0 SEISMIC PROVINCES AND AREA SOURCE ZONES
For the study of seismic hazard in the Gilgit, Nomal and Naltar areas, the Region is divided into
nine seismic zones. The division of the region into these source zones is based on the seismicity,
the fault systems and the stress direction analysis. The division was also based on the data
processing of the whole catalogue regarding the seismicity, depth and the study of research
papers and including the study of geological and seismotectonic maps of the Region.
One of the basic principles for the zonation of a region is that the seismicity within a single zone
remains uniform and homogeneous, even though this principle clearly is not always fulfilled as
judged from the individual catalogues used in the study. The nine seismic zones are all having
geometric shapes (polygons) described below along with Coordinates Figure-17 and zones
Figure-18.
i. Kohistan
ii. Hindukush
iii. Chitral
iv. Main Karakorum Thrust (MKT)
v. Karakoram
vi. Nanga Parbat Massif
vii. Ladakh
viii. Pamir
ix. Himalayas

44
Figure-17. Coordinates of Seismic Zones in Gilgit, Nomal & Naltar
14.1 Kohistan Seismic Zone
Based on the Geology, Seismotectonic Maps, study of research papers and seismic data
catalogue (Figures 6, 7 & 8), the Gilgit, Nomal and Naltar Project study area, is placed in the
Kohistan Seismic Zone. Seismically it is very active seismic zone. Along its northern boarders
Main Karakoram Thrust (MKT) of Eurasian Plate, while along the southern boundaries lays the
Main Mantle Thrust (MMT) of Indian Plate. The Kohistan Seismic Zone is a 30 to 40 km thick
section consisting of metamorphic plutonic and sedimentary rocks.

45
The seismicity plot of Kohistan Seismic Zone (Figure-10) indicates that the whole of the zone is
seismically active with small to moderate seismic events. Also there are some significant clusters
of seismic events present in this active zone. Some densely populated cities of Pakistan and the
capital of Punjab were destructed in 1905 by the devastating Kangra earthquake, which is also
included in this zone.
Figure-18. Seismic Zones in Gilgit, Nomal and Naltar (GNN) Region.
14.2 Hindukush Seismic Zone
This zone entirely covers the Afghanistan region. Several earthquakes with their epicenters in or
around the Hindu Kush ranges have affected the Northern areas of Pakistan. The earthquakes in
1983, 1985 and 1991 in the Hindu Kush had magnitudes 7.4, 7.4 and 6.7, respectively, and it has
been reported that more than 300 people died as a result of these events, in the regions of
Peshawar, Chitral, Swat and Malakand (WAPDA & PMD database). A few records of large
historic earthquakes have also been found in the PMD data base. Any earthquake in Hindu Kush
with magnitude greater or equal to 6 is reported most parts of Northern Pakistan including the
Gilgit-Naltar district.

46
14.3 Pamir Seismic Zone
This is a rectangular-shaped zone covering only the Chinese territories near the Pakistani border
with China. Kongur Tagh (also referred to as Kongur or Kongur Shan) is the highest peak of the
Kunlun Mountains in China.
14.4 Chitral Seismic Zone
This is a very small zone with respect to area and seismicity. It is adjacent to the Hindukush
Seismic Zone. Chitral and Drosh of Pakistan and Asadabad of Afghanistan are the important
cities in this zone.
14.5 Ladakh Seismic Zone
This zone covers mostly the border area of Pakistan, Tajikistan and China. The city of Sost, a
very important town on the Karakoram Highway and the Kunjarab pass are both located in this
zone, as well as a small area of the province of China, Xinjiang. Tashkurgan is a Tajik town in
western Xinjiang, China.
14.6 Main Karakoram Thrust (MKT) Seismic Zone
The Harvard and ISC catalogues contain three earthquakes each having M ≥ 6.0 whereas the
PMD historic database has no significant reports from this zone.
14.7 Karakoram Seismic Zone
It is not a densely populated zone but some seismic activity is present. The seismicity is mostly
concentrated in the Northern side of this seismic zone. The historic data catalogue places some
earthquakes located from this zone. Seismically the area quite since long period of time.
14.8 Himalaya Seismic Zone
It is an important seismic zone and mostly seismicity is present along the northwestern side of
this zone.
14.9 Nanga Parbat Haramosh Massifs Seismic Zone
The Nanga Parbat Haramosh massif (NPHM) is a unique structural and topographic structure in
the northwestern corner of the Himalayan convergence zone. This is an important seismic zone
that is including the syntaxial bend, MMT and Riakot Sassi faults. Some significant earthquakes
> magnitude 5.5 have originated from this seismic zone.

47
15.0 SEISMIC PARAMETERS
“b value” module in connection with “epimap” module of SEISAN software was utilized. The
basic input for SHA is the source model, expressed through the Gutenberg-Richter activity
parameters ‘a’ and ‘b’ for all the seismic source zones. Using the catalogue these were evaluated.
These two basic parameters have been given in Table-1 for each of the nine zones.
The historical earthquakes were dealt when deciding the maximum magnitude potential (Mmax)
of a source zone or in another case, any fault. The plot of recorded earthquakes showed some
association of seismicity with various tectonic features but in most of the cases, association of
earthquake with a particular tectonic feature was quite difficult and with the experience, it has
been found that their contribution in PSHA is rather small. So it was presumed that the
earthquakes were expected to happen at random anywhere over the area.
Then the seismicity model of the study on zone basis was determined. It also carried the basic
inputs of the software EZ-FRISK, to be used later on.
Results of magnitude of completeness were very helpful along with the distribution of
cumulative number of earthquakes corresponding to various magnitude ranges to decide for
minimum magnitude parameter. The maximum magnitude (M max) for different sources was
also crucial for the hazard level, so they were determined after the careful analysis of seismicity
catalogue in combination with the seismicity map.
Distribution of earthquakes is assumed to be uniform within the seismic source zone and
independent of time. Each of these area sources was assigned a maximum magnitude based on
recorded seismicity and potential of the faults within the zone and a minimum magnitude based
on threshold magnitude observed in the magnitude-frequency curve for the zone (b Value).
15.1 Focal depths
The focal depths of earthquakes vary from the shallow to deep in the whole study area, as shown
in Fig. 5-3 for all of the nine zones defined in this study. It is found that from north to south the
depths and mechanism of earthquakes are different in different seismic zones.
Generally the seismicity of Northern Pakistan, except for Hindukush Seismic Zone, is considered
to be of shallow and intermediate depths. This great range of focal depths is a particular
challenge with respect to the choice of ground-motion models to be used in the hazard
calculations.

48
As the shallow earthquakes are of more concern to seismic hazard, the minimum depth of the
earthquakes is taken as 5-10 km for all area sources, except for Hindukush Seismic Zone (SSZ)
for which it is taken as 70 km.
Zone
No
Seismic Source
Zone
No. of
Earthquakes
above
Min.
Magnitude
Minimum
Magnitude
Mw
Activity
Rate
/Year
b
Value
a
Value
Maximum
Magnitude
Mw
1 Hindukush 796 4.0 97.192 1.177 6.796 8.0
2 Karakorum 14 3.9 2.473 1.033 4.520 7.5
3 Kohistan 499 4.0 8.754 1.090 5.532 7.5
4 Nanga Parbat 141 4.0 2.474 1.045 4.736 7.6
5 Himalayas 66 4.0 9.210 1.188 5.833 7.5
6 Ladakh 72 4.0 1.263 1.022 4.260 7.5
7 MKT 133 4.1 2.333 1.004 4.409 7.5
8 Pamir 37 4.1 3.561 1.002 4.587 7.5
9 Chitral 73 4.1 7.456 1.014 5.006 7.8
Table-1. Computed Parameters of Seismic Source Zones within Gilgit-Naltar Region.
16.0 SEISMIC MICROZONATION MASTER PLAN 2040
The study area for “Seismic Microzonation Master Plan 2040” includes Gilgit city, Nomal valley
and Naltar valley.
Gilgit is located at the foothills of the Karakoram Mountains, roughly at the junction between the
three mountain ranges. The average altitude of the city is 1500 meters (m). Gilgit is surrounded
by steep mountains with little or no vegetative cover. It lies at the intersection of the Gilgit and
Hunza Rivers at a place locally known as Duo Pani (two waters types). It is surrounded by peaks
that range from 1,600 m to 2,000 m on either side of the valley (Figure-19).

49
Figure-19. Location of Duo Pani Area of Gilgit city.
The total area covered by Gilgit city is around 38,000 km2 (Gilgit-Wikipedia). The city is spread
longitudinally along the northern and southern banks of the Gilgit River. The southern bank of
the river mainly contains the historic city center with commercial areas, administrative buildings,
an airport, bus stands, historic settlements, open recreation areas and a polo ground. The north
bank of the river is fed by the Konudas Nullah and has an administrative core called Konudas.
There is a settlement in this region called Mujahid Colony and the newly constructed Karakoram
International University (KIU) is also located on this side of the city.

50
Figure-20. Map Showing Different Area Connection of Gilgit City.
Nomal is a small valley located at a distance of 25 km north of Gilgit city in the Gilgit District,
of GB. The valley is also connected with Nalter Bala and Nalter Pain through a metaled road.
The average altitude of the city is 1582 meters (m). The valley is around 19 km in length
northeast and 4.8 km wide, making a total area of about 80 km2. The climate is intensely cold in
winter, with heavy snow fall. In spring and summer seasons when the temperature becomes high
this snow and glaciers melts and water flow towards the inhabited area. The water reservoir is in
the middle of the village and is fed by a five km long open channel (Nomal Valley-Wikipedia).
Naltar is a valley near Gilgit, Hunza and Nomal of GB. Naltar is about 54 km from Gilgit and
can be reached by jeeps. The road is at times blocked by landslides. It is a densely pine forest
region known for its dramatic mountain scenery. There are four lakes in this valley identified as
Bashkiri Lakes making the Naltar River at altitudes ranging from 3,050 m to 3,150 m. The valley
occupies an area of around 270 km2 and is adjoined by two other protected areas, Sher Quillah
Game Reserve and Pakora Game Reserve. The total computed area of all three being in excess of
500 km2 (SCO web site & Naltar Valley-Wikipedia).

51
16.1 Classification of Areas for Microzonation of Gilgit, Nomal and Naltar
After the study of Geological maps, Seismotectonic maps, Borehole Logs of various locations,
Research Papers/Reports, Previous Geophysical Resistivity Survey Reports, Population Growth
trend, Land Growth trend, Built-in trend and previous Master Plan reports, the study area has
been classified into following six seismic units.
1. Naltar Valley
2. Nomal Valley
Gilgit City Sub-Units
3. Gilgit Central City
4. Danyor (including Karakoram International University (KIU), Jalalabad and Sultanabad)
5. Sakwar (including Jutial and Minawar)
6. Gilgit Entrance (intersection of Gilgit & KKH roads)
16.1.1 Naltar Valley Seismic Unit
Naltar valley (36.16 North & 74.17 East, Elev. = 2950 meters), and about 54 km from Gilgit and
can be reached by jeeps. Naltar Bala and Naltar Pine are two villages of Naltar valley. Naltar
Pine is at a distance of around 34 km and Naltar Bala at about 40 km from Gilgit.
The geology of the area is dominantly characterized by sub aerial fore-arc basaltic andesite,
rhyolite, ignimbrite and volcanic clastic sedimentary rocks. There are also Chalt group (Abtain-
blain), rocks and related calac-alkaline andisites, high-Mg tholleiites and boninites. Rakaposhi
volcanic Formation and lower part of the Baumaharel Formation are also exposed.
16.1.2 Nomal Valley Seismic Unit
Nomal is a small valley located at a distance of 25 km north of Gilgit city (36.12 N & 74.18 E).
The valley is also connected with Nalter Bala and Nalter Pain through a metaled road. Old silk
road between Pakistan and China passes through the Nomal valley. Shina and Brushaski are
spoken by the people and all inhabitants of the valley are adherents of Islam. The Nalter River
flows through the northern end of the valley, which also supplies water to the entire valley, while
the river eventually merges with the Hunza River.
Mostly mafic rocks (basalt) are observed here. Grain size was fine and foliation is present in the
rocks. Green color patches are also observed that may be chlorine formed by metamorphism.

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