REVIEW OF RECENT EARTHQUAKES IN THE LIGHT OF PLATE TECTONICS AND SEISMIC RISK STUDY FOR BANGLADESH

WELCOME TO
OUR PRESENTATION ON
REVIEW OF RECENT EARTHQUAKES
IN THE LIGHT OF PLATE TECTONICS
AND SEISMIC RISK STUDY FOR
BANGLADESH

Presented By:
Engr. Souptik Barman Tirtha
Engr. Johana Sharmin

PLATE TECTONICS
• Plate tectonics is the process by which rock material is
moved from within the earth to its surface and, in some
cases, back to its interior and by which the lithosphere is
broken into a series of plates that move with respect to one
another.

EARTHQUAKE: WHY AND HOW?
• An earthquake is caused by a sudden slip on a fault.
• The tectonic plates are always slowly moving, but they get
stuck at their edges due to friction. When the stress on the
edge overcomes the friction, there is an earthquake that
releases energy in waves that travel through the earth's crust
and cause the shaking that we feel.

EARTHQUAKE: WHY AND HOW?
• As tectonic plates move relative to
each other, elastic strain energy
builds up along their edges in the
rocks along fault planes.
• Great amounts of energy can be
stored along the fault and
deformation occurs.
• When the shearing stresses
induced in the rocks on the fault
planes exceed the shear strength of
the rock, rupture occurs.
• Sudden movement occurs along
the fault, releasing the
accumulated energy, and the rocks
snap back to their original
undeformed shape.

SEISMIC WAVES
• Seismic waves are the vibrations or waves of energy created by rock
fracture from earthquakes that travel through the Earth.
• Seismology- the study of earthquakes and seismic waves
• Seismographs- instruments for recording seismic waves from
earthquakes; record a zigzag trace that shows the varying amplitude of
ground oscillations beneath the instrument.
• Sensitive seismographs, which greatly magnify these ground motions,
can detect strong earthquakes from sources anywhere in the world.

SEISMIC WAVES
• Recordings of seismographs are called seismograms.
• Seismograms show:
– Amplitude of seismic waves (how much rock moves or vibrates)
– Distance to the epicenter
– Earthquake direction
• Types of Seismic Waves
– Body Waves (travel through the earth’s interior – P wave and S
wave)
– Surface Waves (travel along the earth’s surface – L wave and R
wave)

SEISMIC WAVES
Type and Name Particle Motion Typical Velocity
Other
Characteristics
P wave (Primary,
Longitudinal)
Alternating
compressions
(pushes) and
dilations (pulls)
which are directed
in the same
direction as the
wave propagating
Vp~ 5-7km/s in
typical earth crust;
>8 km/s in mantle
and core; 1.5 km/s
in water; 0.3 km/s
in air
•Travels fastest in
materials
•Material returns to
its original shape
after wave passes
•First arriving
energy on a
seismogram
•Smaller and higher
frequency
•Can move through
solid rock and
fluids

SEISMIC WAVES
Other
Characteristics
S wave (Secondary,
Transverse)
Alternating
transverse motions
which are
perpendicular to
the direction of
propagation
Vs~ 3-4 km/s in
typical earth crust;
>4.5 km/s in
mantle ; ~2.5-3.0
km/s in solid inner
core
•Travels slower
than P waves
•Arrives after P
waves
•Do not travel
through fluids or in
air or in water or
magma
•Materials return to
its original shape
after wave passes

SEISMIC WAVES
Deformation
propagates
Deformation
propagates

SEISMIC WAVES
Other
Characteristics
L wave (Love
Surface Waves,
Long Waves)
Transverse
horizontal motion,
perpendicular to
the direction of
propagation
VL ~2.5-4.5 km/s in
the earth depending
on frequency of the
propagating wave
•Love wave exists
because of the
earth’s surface
•Largest at the
surface and
decrease in
amplitude with
depth
•Wave velocity is
dependent on
frequencies
•Fastest surface
wave

SEISMIC WAVES
Other
Characteristics
R wave (Rayleigh
wave, Long waves,
Ground roll)
Motion is both in
the direction of
propagation and
perpendicular
Vr~2.0-4.5 km/s in
the earth depending
on frequency of the
propagating wave
•Dispersive and
amplitudes
generally decrease
with depth
•Appearance and
particle motion are
similar to water
waves
•Most of the
shaking felt is due
to this wave, which
can be larger than
the other waves

Both P and S wave
velocities are
inversely
proportional to the
square root of
density
Material P wave velocity S wave velocity
Air 332
Water 1400-1500
Petroleum 1300-1400
Steel 6100 3500
Concrete 3600 2000
Granite 5500-5900 2800-3000
Basalt 6400 3200
Sandstone 1400-4300 700-2800
Limestone 5900-6100 2800-3000
Sand
(Unsaturated)
200-1000 80-400
Sand (Saturated) 800-2200 320-880
Clay 1000-2500 400-1000
Glacial Till
(Saturated)
1500-2500 600-1000
SEISMIC WAVE SPEED

DEPTH OF EARTHQUAKE
Shallow Intermediate Deep
Depth (from
surface)
0-70 km 70-300 km 300-700 km

EARTHQUAKE MAGNITUDE SCALE
• It is a measure of earthquake size and is determined from
logarithm of the maximum displacement or amplitude of
the earthquake signal as seen on the seismogram, with a
correction for the distance between the focus and the
seismometer.
• The scales commonly used:
– Local (or Richter) magnitude (ML)
– Surface- wave magnitude (Ms)
– Body wave magnitude (MB)
– Moment Magnitude (Mw)

• Local (Richter) Magnitude (ML)
– Richter magnitude was the first widely used instrumental magnitude
scale to be applied in the USA (Richter, 1935).
– The scale is based on the amplitude (in mm) of the largest seismogram
wave trace on a Wood- Anderson seismograph (free period 0.8s),
normalized to a standard epicentral distance of 100km.
– Richter defined his magnitude 0 earthquake as that which produced a
maximum amplitude of 0.001 mm at a distance 100 km.
– Each successively layer magnitude was defined as a 10-fold increase
in amplitude beyond the base level.
– Thus a maximum seismogram amplitude (at a distance of 100 km) of
0.01 mm represents M 1.0, 0.1 mm equals M 2.0, 1mm equals M 3.0,
and so on.
– Richter magnitude scale accurately reflects the amount of seismic
energy released by an earthquake up to about 6.5.

• Surface Wave Magnitude (MS)
– The surface wave magnitude scale was developed to solve the
saturation problem of Richter magnitude above M 6.5.
– The measurement procedure is similar to measure the Richter
magnitude, except that the peak wave amplitude is measured for
surface waves that have periods of 20 sec.
• Body Wave Magnitude (MbLf )
– The sort period body-wave magnitude is the principal magnitude
used in the tectonically stable eastern part of North America and
Canada. This magnitude is measured from peak motions
recorded at distances up to 1000 km on instruments.
• Moment Magnitude (Mw)
– This is fundamentally different from the earlier scales. Rather
than relying on measured seismogram peaks, the Mw scale is
tied to the seismic moment (Mo) of an earthquake.

HOW ARE EARTHQUAKE
MAGNITUDES MEASURED?
• Richter Scale
– Locating the epicenter
• Measuring the S-P time interval

HOW ARE EARTHQUAKE
• Richter Scale
• Determining the earthquake distance

HOW ARE EARTHQUAKE
• Richter Scale
• Finding the Epicenter on a map

HOW ARE EARTHQUAKE
• Richter Scale
– Measuring Magnitude
• Measure the distance between the
first P and S wave.
• Find the point for time interval on
the left side of the chart below and
mark that point.
• Measure the amplitude of the
strongest wave. Find amplitude on
the right side of the chart and mark
the point.
• Place the ruler on the chart between
the points you marked for the
distance to the epicenter and the
amplitude. The point where the
ruler crosses the middle line on the
chart marks the magnitude
(strength) of the earthquake.

HOW ARE EARTHQUAKE
• Richter Scale
– Measuring Magnitude
• Empirical Formula:
Where A is the maximum excursion of the Wood-Anderson
seismograph, the empirical function Ao depends only on the
epicentral distance of the station, δ. Because of the logarithmic
basis of the scale, each whole number increase in magnitude
represents a ten fold increase in measured amplitude; in terms of
energy, each whole number increase corresponds to an increase
of about 31.6 times the amount of energy released, and each
increase of 0.2 corresponds to a doubling of the energy released.

HOW ARE EARTHQUAKE
• Moment Magnitude Scale
– Unfortunately, Richter scale do not provide accurate estimates for
larger magnitude earthquakes. Today the moment magnitude scale is
preferred because it works over a wider range of earthquake sizes and
is applicable globally.
– The moment magnitude scale is based on the total moment release of
the earthquake. Moment is a product of the distance a fault moved and
force required to move it. It is derived from modeling recordings of
the earthquake at multiple stations.
– Magnitudes are based on a logarithmic scale (base 10). What this
means is that for each whole number you go up on the magnitude
scale, the amplitude of the ground motion recorded by a seismograph
goes up ten times. Using this scale, a magnitude 5 earthquake would
result in ten times the level of ground shaking as a magnitude 4
earthquake.

HOW ARE EARTHQUAKE
• Moment Magnitude Scale
– The symbol for moment magnitude scale is Mw, with the
subscript ‘w’ meaning mechanical work accomplished. The
moment magnitude is a dimensionless number defined by Hiroo
Kanamori as,
Where Mo is the seismic moment in dyne.cm (10-7N.m). The
constant values in the equation are chosen to achieve consistency
with the magnitude values produced by earlier scales.

HOW ARE EARTHQUAKE
• Mercalli Scale
– Another way to measure the strength of an earthquake is to
use the Mercalli scale. Invented by Giuseppe Mercalli in
1902, this scale uses the observations of the people who
experienced the earthquake to estimate its intensity.
– The Mercalli scale is not considered as scientific as the
Richter scale, as it is based on the record of the amount of
damage.
– Some things that affect the amount of damage that occurs
are:
• The building designs
• The distance from the epicenter
• And the type of surface material (rock or dirt) the buildings
rest on.

RELATION BETWEEN MODIFIED MERCALLI
AND RICHTER
Modified Mercalli Scale Richter Scale
Intensity Verbal
Description
Witness
Observation
s
Magnitude Acceleration
(cm/s2)
Observation
s
I Instrumental Detected
only by
seismograph
s
2.5 <1 Generally
not felt, but
recorded on
seismometer
s
II Feeble Noticed
only by
sensitive
people

AND RICHTER
Intensity Verbal
Description
Witness
Observations
(cm/s2)
Observations
III Slight Resembling
vibrations
caused by
heavy traffic
3.5 2.5 Felt by many
people
IV Moderate Felt by
people
walking;
rocking of
free standing
objects
V Rather
Strong
Sleepers
awakened
and bells ring

AND RICHTER
Intensity Verbal
Description
Witness
Observatio
ns
Magnitude Acceleratio
n (cm/s2)
Observatio
ns
VI Strong Trees sway,
some
damage
from
overturning
and falling
object
4.5 10-50 Some local
damage
may occur
VII Very Strong General
alarm,
cracking of
walls

AND RICHTER
Intensity Verbal
Description
Witness
Observation
s
n (cm/s2)
Observation
s
VIII Destructive Chimneys
fall and
there is
some
damage to
buildings
6.0 100-250 A
destructive
earthquake
IX Ruinous Ground
begins to
crack,
houses
begin to
collapse
and pipes
break

AND RICHTER
Intensity Verbal
Description
Witness
Observation
s
n (cm/s2)
Observation
s
X Disastrous Ground
badly
cracked and
many
buildings
are
destroyed
and there
are some
landslides
7.0 500 A major
earthquake

RELATION BETWEEN MODIFIED MERCALLI AND RICHTER
Intensity Verbal
Description
Witness
Observations
(cm/s2)
Observations
XI Very
Disastrous
Few buildings
remain
standing;
bridges and
railways
destroyed;
water, gas,
electricity and
telephones
out of action
8.0 and up 750-900 Great
earthquake
XII Catastrophic Total
destruction;
objects are
thrown into
the air, much
heaving,
shaking and
distortion of
the ground

PEAK GROUND ACCELERATION (PGA)
• Definition: PGA is equal to the maximum ground acceleration
that occurred during earthquake shaking at a location.
• PGA or earthquake shaking generally occurs in three
directions:
– Horizontal components of two perpendicular directions (NS and
EW)
– Vertical component of one direction (up and down)
• Horizontal PGAs are generally larger than those in the
vertical direction (except: large earthquakes).
• Peak horizontal acceleration (PHA) is the most commonly
used type of ground acceleration in engineering applications.
In an earthquake, damage to buildings and infrastructure is
related more closely to ground motion rather than the
magnitude of the earthquake itself.

• As stress waves spread out and travel from the focus
through the soil media, energy is dissipated in two ways:
– Due to material damping
– Due to radiation damping
• Analysis of the simplified models of the Earth’s crust
has yielded the following results:
– Body waves decay at the rate of 1/r
– Surface waves decay at the rate of 1/√r
where r = radial distance from the focus
– Surface waves decay at a much slower rate and can travel
a considerable distance where tremors may be felt. In the
Mexico city (1985) earthquake the surface waves travelled
approximately 400km and damaged many buildings.

Instrumental
Intensity
Acceleration
(g)
Velocity
(cm/s)
Perceived
Shaking
Potential
Damage
I < 0.0017 < 0.1 Not felt None
II-III
0.0017 -
0.014
0.1 - 1.1 Weak None
IV 0.014 - 0.039 1.1 - 3.4 Light None
V 0.039 - 0.092 3.4 - 8.1 Moderate Very light
VI 0.092 - 0.18 8.1 - 16 Strong Light
VII 0.18 - 0.34 16 - 31 Very strong Moderate
VIII 0.34 - 0.65 31 - 60 Severe
Moderate to
heavy
IX 0.65 - 1.24 60 - 116 Violent Heavy
X+ > 1.24 > 116 Extreme Very heavy

PLATE BOUNDARIES
• Divergent boundaries or constructive plate margin--
where new crust is generated as the plates pull away
from each other.
• Convergent boundaries or destructive plate margin-
- where crust is destroyed as one plate dives under
another.
• Transform boundaries or conservative plate
margin -- where crust is neither produced nor
destroyed as the plates slide horizontally past each
other.

CONVERGENT BOUNDARY- REASON OF
ARISING OF HIMALAYA AND OCCURANCE OF
EARTHQUAKES FOR ALPIDE BELT

CONVERGENT BOUNDARY- REASON OF
FORMATION OF PACIFIC RING OF FIRE
 At eastern section: Nazca
Plate and Cocos
Plate being subducted beneath
South American Plate.
 A portion of the Pacific
Plate along with the small Juan de
Fuca Plate are being subducted
beneath the North American Plate.
 At west: Pacific plate is being
subducted along the Kamchatka
Peninsula arcs on south past Japan.
 The southern portion is more
complex, with a number of smaller
tectonic plates in collision with the
Pacific plate.

DISTRIBUTION OF MAJOR EARTHQUAKES IN THE
WORLD- PROOF OF RING OF FIRE AND ALPIDE
BELT

JAPAN EARTHQUAKE - 15TH
APRIL, 2016
• Magnitude – 7.0
• Depth – 10 ± 1.9km
• Minimum Distance – 40.5km
• Region of Focus and Epicenter –
Kyushu, Japan
• Japan’s Tectonic Position:
– Japan’s stretch of the Ring of
Fire is where the North
American, Pacific, Eurasian
and Philippine plates come
together.
– Japan is situated in a
complicated plate boundary
region where three subduction
zones meet.

JAPAN EARTHQUAKE - 15TH APRIL,
2016
 To the south, the Philippine plate is
being subducted beneath the Eurasian
plate, whilst to the north, the Pacific
Plate is being subducted beneath the
North American plate.
 Northern Japan is largely on top of the
western tip of the North American plate.
Southern Japan mostly above the
Eurasian plate.
 On average, the Pacific Plate is moving
west at about 3.5 inches (8.9
centimeters) per year, and the movement
has produced major earthquakes in the
past nine earthquakes of magnitude 7 or
greater since 1973.

APRIL, 2016
Earthquake aftermath:
Rupture: The rupture during Friday's quake was almost
200 miles long, on an underwater fault that is about 220
miles long by about 60 miles wide.
Movement of plate and island: Japan's Earthquake
Research Committee said the earthquake forced the North
American plate eastward by about 66 feet. The entire
island of Honshu was moved about 8 feet east, according
to USGS scientists.
Explosive eruptions: About 950 miles south of Friday's
earthquake, the Shinmoedake cone on the Kirishima
mountain range erupted on Sunday.

APRIL, 2016
Figure: Interactive Map Figure: Intensity Map

ECUADOR EARTHQUAKE - 16TH APRIL,
2016
• Depth – 19.2 ± 3.4km
• Region of Focus and Epicenter
– Santo Domingo do Los
Colorados, Ecuador
• Ecuador’s Tectonic Position:
– It lies on the boundary of
the Nazca and South
American tectonic plates.
– The Nazca plate lies under
the section of the Pacific
Ocean just west of South
America.

2016
• Relative to a fixed South
America plate, the Nazca plate
moves slightly north of
eastwards at a rate varying
from approximately 80 mm/yr
in the south to approximately
65 mm/yr in the north.
• Instead of originating at a
single point, this earthquake
was likely caused by a rupture
along the plate boundary that
stretched over a 99 mile long
by 37 mile wide area, roughly
12 miles under the Earth's
surface.

2016

ONLY REASON OF SUCCESSIVE EARTHQUAKES
IN JAPAN AND ECUADOR – POSITION OF THEM IN
“RING OF FIRE”

MYANMAR EARTHQUAKE - 13TH APRIL,
2016
• Depth – 134.8 ± 6.1km
• Region of Focus and Epicenter –
Myanmar
• Myanmar’s Tectonic Position:
– The Sagaing Fault is a major
tectonic structure that cuts
through the centre of Myanmar
(formerly known as Burma),
broadly dividing the country into
a western half moving north with
the Indian plate, and an eastern
half attached to the Eurasian
plate.

2016
• The earthquake occurred as the result of oblique reverse faulting at an
intermediate depth, approximately 140 km beneath western Burma. The
epicenter of the earthquake is located some 500 km to the northeast of the Sunda
Trench, where lithosphere of the India plate begins subducting to the northeast
beneath Sunda and Eurasia.
• At the location of this earthquake, the India plate moves north-northeast with
respect to the Sunda and Eurasia plates, at a velocity of 44-49 mm/yr.

2016

TECTONIC FRAMEWORK OF BANGLADESH-
GEOMORPHLOGICAL CONCEPT
• In 1982, Martin and Husain prepared a tectonic scheme
for Bangladesh and adjacent areas based on historical-
genetic and plate tectonic principles whereas the previous
maps were based on only geomorphological concept. The
outlines are described below:
The Bengal Basin is subdivided into two principal units: (1)
the western and northwestern gentle sloping stable shelf on
the Indian Craton and (2) the deep basinal area- the Bengal
Foredeep- to the east and the southeast.
Through Bangladesh, the NE-SW trending Hinge Zone
with a width of 25-30 km passes through the Calcutta-
Pabna- Mymensingh gravity high and further NE across the
Dauki Fault to the Naga Hills region of Assam.

GEOMORPHOLOGICAL CONCEPT
 The Bengal Foredeep is a low
gravity feature located
between the Hinge Zone on
the west and the Barisal-
Chandpur Gravity High in the
east. It extends from south of
the Shillong Plateau to the
Bay of Bengal and two
troughs are situated in this
foredeep namely, the Sylhet
Trough on the northeast and
the Faridpur Trough on the
northwest and the Madhupur
High separates the two.

GEOMORPHOLOGICAL CONCEPT
 The Main Boundary thrust
Fault (MBT) initiated in
late Miocene or Pliocene
time is regarded as the
present thrust front of the
Himalayas and forms the
northern margin of the
Himalayan foredeep.
 The Bengal Basin is
bounded on the east by the
western fold belt of the
Indo-Burma ranges.

TECTONIC PLATE CONCEPT
 Bangladesh lies on the northeastern Indian plate, near the edge
of the Indian craton and at the junction of three tectonic plates
– the Indian plate, the Eurasian plate and the Burmese
microplate. These form two boundaries where plates converge-
the India Eurasia plate boundary to the north forming the
Himalayan arc, and the India Burma plate boundary to the east
forming the Burma arc.
 The Indian plate is moving at a rate of 6 cm per year in a
northeast direction, and subducting under the Eurasian and the
Burmese plate in the north and east, at a rate of 45mm per year
and 35mm per year, respectively.

 To the north, the collision between the Indian and Eurasian
plates has created the Himalayan Mountains. This great north
dipping thrust fault runs more than 2000km from Pakistan to
Assam and has produced many large continental earthquakes
over the past millennium. The 500km long section just 60km
north of Bangladesh, however, has not produced a great
earthquake in the past several hundred years.
 The other major tectonic belt of Bangladesh appears along the
country’s eastern side. The Arakan subduction- collision
system invloves oblique convergence of the Indian and Burma
plates.

WHAT IS FAULT?
Fault:
A fracture in rock along which there has been an
observable amount of displacement. It is customary to
describe a fault according to the relationship of the
fault-strike and bedding strike:
(a) fault strike parallel to the bedding strike = strike
slip fault
(b) fault- strike approximately at right angles to the
bedding strike = dip slip fault
(c) fault-strike making a well-defined angle with the
bedding strike = oblique slip fault.

TYPES OF FAULTS
Fig.: Strike- Slip
Fault
Fig.: Normal Fault Fig.: Reverse Fault
Fig.: Dip Slip Fault
Fig.: Oblique Slip
Fault

FAULTS IN BANGLADESH
• Normal Fault:
A fault in which the hanging wall is on the
downthrow side. Normal faults are sometimes
referred to as tension or gravity faults. In
Bangladesh Bogra fault is a normal fault which
has been active at different times and located in
the Western Foreland Shelf. The Hinge zone, a
zone of deep seated normal faults in the basement
complex is conventionally thought of as
representating the dividing line between the Indian
platform and the Bengal Foredeep. This zone is
seismically active and the focus of earthquake
possibly originating with this zone have depth
ranges from 71 to 150 km.

• Reverse Fault:
This is one in which the hanging wall moves upward
in relation to the footwall. In Bangladesh, thrust faults
are commonly associated with the anticlinal folds of
the eastern fold belts. In fact the eastern fold belt of
the Chittagong-Tripura is a fold thrust belt owing its
origin to the subduction of the Indian plate beneath the
Burmese plate.
• Strike Slip Fault:
Strike-slip Fault are those along which the
displacement is chiefly parallel to the strike of the
fault. Kaladan fault covers a distance of almost 270-
km marked the eastern boundary of the Mizoram-
Tripura-Chittagong folded belt.

• En-echelon Fault:
Sometimes gravity faults show an en echelon pattern where
individual faults strike at an angle of approximately 45 degrees to
the trend of the faulted belt as a whole. The fresh en-echelon fault
scarps along the most western edges of the Madhupur Tract bear
geomorphic characteristics of recent tectonism. The most
remarkable features of the Shillong Plateau is the E-W running
Dauki fault which marks the southern margin of the plateau. The
steep escarpment indicates vertical displacement along the Dauki
Fault Zone where the Bangladesh plains subside actively. Though
the Dauki Fault Zone is shown as a single fault line on the
geological map of Bangladesh (1990) but the images show that it is
the combination of a number of en-echelon faults trending NW-SE,
NE-SW and N-S, hence the fault scraps are zigzag rather than a
straight line.

FAULT BOUNDARIES UNDERNEATH
BANGLADESH

FAULT BOUNDARIES UNDERNEATH
BANGLADESH
• Estimated Max magnitude: 7.5Madhupur Fault
• Estimated Max magnitude: 8.0Dauki Fault
• Estimated Max magnitude: 8.5
Plate Boundary
Fault 1
Plate Boundary
Fault 2
Plate Boundary
Fault 3

ACTIVE FAULT ZONES NEAR
BANGLADESH

ACTIVE FAULT ZONES NEAR
BANGLADESH
• Number of earthquakes= 685, Mmax=
8.7Assam fault zone
• Number of earthquakes= 1330,
Mmax= 7.7Tripura fault zone
7.6
Sub-Dauki fault
zone
7.0Bogra fault zone
5.7
Coastal fault
zone

GROUND MOTION OF FAULTS IN
BANGLADESH
According to the Hazard, Vulnerability, Risk Assessment
undertaken by Bangladesh Urban Earthquake Resilience
Program (BUERP), all areas of Dhaka are subject to
potentially strong ground motion.
Madhupur fault is to the north of the city. Ground
motions generally decrease from north to south and are
amplified in areas of soft soil.
The plate boundary 2 fault is to the east of the city and
ground motions decrease going east to west.
Magnitude 6 event under Dhaka has the highest ground
motion near the arbitrary location of the fault.

GROUND MOTION OF FAULTS IN
BANGLADESH

TECTONIC FRAMEWORK OF DHAKA
Dhaka is located in the
Dhaka (semi-folded) sub
zone of the Internal Zone
of Bengal foredeep. On
the north it is bordered by
Tangail Tripura High, on
the east Chittagong
(folded) subzone, on the
west by Hinge subzone
and on the south
Patuakhali trough (1986,
New concepts on the
Tectonic Zonation of
Bengal foredeep).

There are two well-
known distinct geologic
features in Dhaka city:
The uplifted block of
the Madhupur tract
The floodplain
deposits that surround
the Madhupur tract
(deposits consist of
alluvial sand, silt and
clay and the thickness
of the deposits ranges
from 6 to 15 metres)

According to the Geological Survey of Bangladesh:
Stable areas
Kotwali
Motijheel
Syedabad
Kamlapur
Shegunbagicha
Kakrail
Dhanmondi
Gulshan
Banani
Uttara
Mirpur- 1,2,3,6,12
Unstable areas
Meradia
Shatarkul
Badda
Bhatara
Mirpur 14
Botanical garden
Kalyanpur
Mohammadpur
Pallabi
Kalapani

STABLE AND UNSTABLE AREAS OF DHAKA
ACCORDING TO GEOLOGICAL SURVEY

But from a geotectonic perspective, however, both
categories of areas are at a greater risk for
constructing high rise buildings and other structures.
Dhaka city is highly vulnerable to earthquakes
because it sees numerous active and dominant fault
lines, which are the weak points for potential
earthquake damage. These fault lines include those at
Tongi, Pagla, Balu, Baunid, Dhamrai, Kaliakair,
Turag, Shitalakhya lineament, Arial Khan lineament,
Banar, Old Brahmaputra, Buriganga, Bansi,
Modhupur, Dhaleswari and the Padma.

Dhaka has been
identified as one of the
20 most vulnerable
cities to seismic risk in
the world. The nearest
major fault line is
believed to run less
than 60km from
Dhaka, and although
there is some
uncertainty, research
suggests that an
earthquake of up to
magnitude 7.5 is
possible.

HISTORICAL EARTHQUAKE AFFECTED
BANGLADESH
Year Name Magnitude
Distance from
Capital(km)
Affected Area
1869
Cachar
Earthquake
7.5 250
Assam,
Monipur, Sylhet
1885
Bengal
Earthquake
7.0 170
Jamalpur,
Mymensing,
Bogra
1897
Great Indian
Earthquake
8.7 230
Assam, Sylhet,
Rangpur
1918
Srimangal
Earthquake
7.6 150
Whole Sylhet to
Dhaka
1930
Dubri
Earthquake
7.1 250 Rangpur
1934
Bihar-Nepal
Earthquake
8.3 510
Nepal, India,
Bangladesh
1950
Assam
Earthquake
8.5 780
Assam, Whole
Bangladesh

HISTORICAL EARTHQUAKE AFFECTED
BANGLADESH
Year
Name
Magnitude
Distance
from
Capital(km)
Affected
Area
1987
Sylhet
Earthquake
5.6 200
Northern
Bangladesh
1997
Bandarban
Earthquake
6.0 325
South-eastern
part
1999
Maheskhali
Earthquake
5.1 350 Maheskhali
2003
Barkal
Earthquake
5.1 350 Barkal
2015
Nepal
Earthquake
7.9 745
Nepal, India,
Bangladesh

ISOSEISMAL MAP OF ASSAM
EARTHQUAKE, 1950
ISOSEISMAL MAP OF BENGAL
EARTHQUAKE, 1885

ISOSEISMAL MAP OF BIHAR-NEPAL
EARTHQUAKE, 1934
ISOSEISMAL MAP OF SRIMANGAL
EARTHQUAKE, 1987

INTENSITY MAP OF NEPAL EARTHQUAKE, 2015

LARGE EARTHQUAKES IN HISTORY OF
BANGLADESH
Name Source of Area
Arakan Earthquake
(1762, M 8.5)
Arakan segment
Bengal Earthquake
(1822, M 7.1)
CTFB
Cachar Earthquake
(1869, M 8.1)
Indo-Burman
ranges
Great Assam
Earthquake (1897,
M8.0)
Dauki fault
Srimongol
Earthquake (1918,
M 7.4)
CTFB

EARTHQUAKES IMPACTING DHAKA
• Bengal earthquake, 1885,
magnitude 7
• Great Indian earthquake, 1918,
magnitude 7.6
Intensity
VIII
• Srimangal earthquake, 1918,
magnitude 7.6
Intensity
VII
• 1923, magnitude 7.1
Intensity
VI

FAULT RECURRENCE INTERVAL IN BANGLADESH
Fault
Length
(km)
Dip
(degree)
Slip rate
(mm/year)
Rupture
area (sq
km)
Recurrenc
e interval
(years)
Probabilit
y of
occurrence
within 50
years
Dauki
Fault
260 45 10 350 350-650 7.7%
Tripura
Segement
250 5 5 2000
Several
thousand
years
(assumed
2000)
5.1%
Arakan
Segment
440 16 23
700
(around)
900 13.4%
CTFB 20-60 - - - ~100 64.9%
Madhupur
Fault
50 45 2 2000
Several
thousand
years (not
assumed)
0%

WHY BANGLADESH IS IN EARTHQUAKE RISK
• Tectonic
Location and
Position of
Faults
• Huge number
of Population
• Unplanned
Buildings over
the City
• Weak
Infrastructure
• Less
Consciousness
of People
• Less Planning
of
Government
• Less Land Use
Planning

PROBABLE EFFECTS OF EARTHQUAKE- IN
GENERAL
• Ground
Shaking
• Damage to
Man-made
Structures
• Fires • Flooding
• Tsunami • Landslides • Liquefaction

REASONS OF VULNERABILITY OF
EARTHQUAKE IN BANGLADESH
Congested
cities
Population
Growth
Old Brick
Buildings
Fire
ignition
problems
from gas
stoves
Risky
Electrical
Wiring
Narrow
Lanes
Narrow
Roads
High Rise
Buildings
Irregular
Buildings
Possibility
of
Pounding

ESTIMATED BUILDING AND CONTENT
LOSSES IN BANGLADESH
0
1000
2000
3000
4000
5000
6000
7000
Madhupur
M7.5
Plate
Boundary 2
M8
M6 under
Dhaka
Building+Contentslosses
($millions)
BUERP research
CDMP results

ESTIMATED BUILDING LOSSES IN DHAKA AND
SYLHET ACCORDING TO CDMP STUDY
0
50000
100000
150000
200000
250000
300000
Dhaka Sylhet
270604
51858
238164
50879
Damaged Beyond repair

ESTIMATED LIFELINE LOSSES IN DHAKA AND
Potable Water Facilities
• Dhaka: 748
• Sylhet: 18
Gas Compression Stations
• Dhaka: 7
• Sylhet: 1
Electrical Power Facilities
• Dhaka: 54815
• Sylhet: 9057
Leaks and Breaks
• Dhaka: 1700
• Sylhet: 219

ESTIMATED LIFELINE LOSSES IN DHAKA AND
Debris
• Dhaka: 72 millions
• Sylhet: 5 millions
Fire
• Dhaka: 107 nos
• Sylhet: 13 nos

ESTIMATED HOSPITAL BEDS AVAILABLEIN DHAKA
AND SYLHET ACCORDING TO CDMP STUDY
59849
7441
Dhaka City
Corporation
Available
(Now)
Available
(Worst
Case
Scenario)
8722
17
Sylhet City
Corporation
Available
(Now)
Available
(Worst
Case
Scenario)

ESTIMATED NUMBER OF FATALITIES IN DHAKA
AND SYLHET ACCORDING TO CDMP STUDY
0
50000
100000
150000
200000
250000
300000
Dhaka Sylhet
260788
20708
183450
14276
During Night (2 AM) During Day (2 PM)

ESTIMATED ECONOMIC LOSSES IN DHAKA AND
Regions
Building Related (in
US$ millions)
Lifelines Related (in
US$ millions)
Dhaka City
Corporation
15,603 364
Sylhet City
Corporation
1105 117

MAGNITUDE AND PROBABILITY OF THE
OCCURRENCE OF EARTHQUAKE SCENARIOS FOR
DHAKA AND SYLHET
Dhaka Sylhet
Scenarios
Magnitude
(Mw)
Probability
Magnitude
(Mw)
Probability
No
Earthquake
0 0.95 0 0.611
1 7.5 0.000575 8 0.003
2 8 0.00257 8.3 0.001
3 6 0.004731 6 0.047
4 8.5 0.001035 8 0.003
5 8.5 0.0014
Others 4.5 0.038462 4.5 0.333

EARTHQUAKE REMEDIAL PLAN FOR
BANGLADESH
• Push over analysis: Safe zone identification of
existing building.
• Corner zoning: to reduce casualty in the cornered
triangular zones.
• 80 grade steel: suitable or not suitable – think.
• Increasing footing area of existing masonry building.
• Provide horizontal concrete band in existing brick
masonry construction.
• Cladding: sense of material choosing for cladding
should be taken into consideration.

EARTHQUAKE REMEDIAL PLAN FOR
BANGLADESH

REFERENCES
• United States Geological Survey (USGS)
• Document on World Bank
• Journal on ‘Seismicity in Bangladesh’ by Dr. Jamilur R. Choudhury, Professor
of Civil Engineering, BUET, Dhaka
• Report on ‘Seismicity and Seismic Hazard Assessment in Bangladesh:
Reference to Code Provisions’ by Dr. Tahmeed Malik Al-Hussaini, Associate
Professor of Civil Engineering, BUET, Dhaka
• Report on ‘Active Fault Mapping in Bangladesh: Paleo-seismological Study of
Dauki Fault and the Indian-Burman Plate Boundary Fault’ by CDMP
• Journal on ‘Earthquake Resistant Non-Engineered Building Construction for
Rural Area in Bangladesh’ by Professor and Graduates of Civil Engineering,
CUET
• Presentation on ‘High Strength Rebar for Concrete Buildings in Bangladesh’
by Dr. Khan Mahmud Amanat, Professor of Civil Engineering, BUET
• Article on ‘Earthquake: What tectonic map reveals for Bangladesh’ by Meer
Husain and Md Jasim Uddin
• Article on ‘Major Madhupur Fault quake can wreak colossal damage’ by
Anisur Rahman Khan

REVIEW OF RECENT EARTHQUAKES IN THE LIGHT OF PLATE TECTONICS AND SEISMIC RISK STUDY FOR BANGLADESH

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