The Final Seminar of the Project for Assessment of Earthquake Disaster Risk for the Kathmandu Valley in Nepal was held on 14 February 2018. The public seminar was held three times during the project. The Final Seminar, “ Understanding Disaster Risks and Moving Towards DRR and Resilience”, presented on the activities and accomplishment of the project, construction of robust and resilient society against natural disaster risk. Thank you all for your support and enthusiastic participation in this seminar. Presentation: Overview of Hazard Assessment Results

1. 1
14th February 2018
Final Public Seminar
-Understanding Disaster Risk and
Moving Towards DRR and Resilience-
Overview of Hazard Assessment Results
Lok Bijaya Adhikari (NSC/DMG)
Mukunda Bhattarai (NSC/DMG)
THE PROJECT FOR ASSESSMENT OF EARTHQUAKE DISASTER RISK
FOR THE KATHMANDU VALLEY IN NEPAL

2. 2
Contents
Procedure of Seismic Hazard Assessment
Setting of Scenario Earthquakes
Development of Ground Model
Characteristics of Gorkha Earthquake
Assessment Results

3. Bedrock layer
(3) Evaluation of
Bedrock Motion
(2) Ground
Modelling
Deposit Layer
Ground Surface
Seismic Source
Attenuation Equation
3
Response Analysis
(1) Setting of
Scenario Earthquake
(4) Site Response
Analysis
(5) Seismic Motion at Ground Surface
Schematic Image of Seismic Wave
Propagation
(6) Estimation of Liquefaction & Slope Failure

4. 4
KV
SATREPS (Tokyo Univ., DMG) provided the fault model details
M=8.6
M=7.8
M=7.8
M=7.8
M=8.3
Largest
Aftershock
M=7.3
Far-Mid Western
Nepal Scenario Eq.
Model
Western Nepal
Scenario Eq.
Model
Central Nepal
South Scenario
Eq. Model
Gorkha Eq. Model 1934 Eq. Model
Magnitude 8.6 7.8 7.8 7.8 8.3
Type Reverse Reverse Reverse Reverse Reverse
Scenario Earthquake Verification Earthquake
Scenario Earthquake Fault Model
Three Scenario Earthquakes and Two Verification Earthquakes
(set technically, for disaster management purpose)

5. Scenario Earthquakes
Four Scenario Earthquakes for disaster management purpose)

6. 6
2. Conduct Microtremor Measurements for Vs structure
a) 210 single points from Ehime University (existing),
b) 308 single points, 74 L-shape array, 39 three-points array,
c) 5 tripartite large scale array (conducted by this project)
3. Grid size: 250mx250m, 11,934 grids, max depth more than 550m
(2002 project: grid size 500mx500m, 2,826 grids, max 100m depth)
4. Geological structures based on geological cross sections,
and Vs structures based on array microtremor measurements
5. Ground Model at each grid for ground motion analysis
- layer classification, soil type, thickness, Vs, density etc.
6. Preparation of AVS30, Susceptibility maps, Tg, etc.
Development of Ground Model
1. Collect & Produce Ground Information
a) Drilling data (449), PS logging (5),
b) Geotechnical and Geophysical (Gravity Anomaly) data etc.
c) (Produced) Geomorphology map, geological cross sections

7. 1. Originally “mountainous area”
2. Gradually settled due to tectonic movement and formed basin
3. <around one million years ago>
Kathmandu Valley was turned to “Old Kathmandu Lake”
4. Lake deposits were piled as Tarebhir, Lukundol and Kalimati
Layers, etc.
5. <after around 50 thousand year ago>
lake water level changes made several terrace faces such
as Tokha, Gokarna, Thimi and Patan with each elevation level
6. <around 10 thousand years ago? to nowadays>
Lake water flown out from Chobar canyon, and
Recently rivers deposit alluvial layers (sub-surface layers)
along river, forming alluvial plain, valley plain etc.
Brief History of Kathmandu valley
7

8. Geological Cross Sections
E-Line
F-Line
G-Line
Ground Models (soil structure) for Grid System
(for around 12,000 grids of 250mx250m,
maximum depth more than 550m)
Lines1-11
A – N lines
ERAKV 4th JCC WG1 2016/09/14

9. Development of Ground Model
9
Ground Models for Grid System with 250mx250m,
and maximum depth more than 550m Predominant Period
of the ground calculated
from ground model
3 dimensional view
Sediment
Klm
Lkl
Tarebhir
WR
Pashupatinath
Kirtipur
Lalitpur Madhyapur

10. Amplification/Response of Ground
10
Ground
Softness
Predominant
Period
Amplification
at ground
Geomorphology

11. Singularity of the Gorkha Earthquake
11
PGAs observed values were
very less than calculated values
observed≪calculated in PGA
Ratios are
around from 1/5 to 1/3
(main shock),
around from 1/3 to2/3
(largest aftershock)
Correction Factors
are adopted
in the project
50
500
1/4
1/2
Observed
Calculated
PGA(gal)
100
200
2015 Gorkha earthquake
Main Shock largest
aftershock
Ex. Source regions of
1985 Chile and Mexico earthquakes

12. PGA for Scenario Earthquakes
12
The 2015 Gorkha Eq.
(Modification by x1/5)
WN model
Western Nepal Eq.
CNS-1 Model
Central Nepal South Eq.
(Modification by x1/3)
The 1934 Bihar-Nepal Eq.
(No Modification by x1/1)
CNS-2 Model
Central Nepal South Eq.
(Modification by x1/2)
CNS-3 Model
Central Nepal South Eq.
(Modification by X2/3)
200-400gals
250-400gals 250-600gals 300-800gals
Approximately 2 times
Approximately 3 times Approximately 4 times
150-200gals
Similar level
of Gorkha EQ
150-200gals
Almost same

13. 13
Liquefactionresistanceratio(τl/σ’z)or
Equivalentcyclicshearstressratio(τd/σ’z)
Corrected N-value (Na)
FL (Liquefaction Factor) = (force to liquefy)/(resist liquefaction)
FL>1 liquefaction possible
FL<1 liquefaction not possible
PL = depth weighted (1-FL)
Criteria for liquefaction possibility
(Architectural Institute of Japan)
Judgement of liquefaction possibility
PL=0 (O) No possibility
0<PL<=5 (L) Low possibility
5<PL<=15 (M) Moderate possibility
15<PL (H) High possibility
(left)
Depression at Tundhikel
(right)
Fissure in the road to Balaju
during the 1934 Bihar-Nepal
earthquake (Rana, 1935)resist liquefaction
forcetoliquefy

14. Liquefaction during past earthquakes
• 2015 Gorkha Earthquake
– 11 sites of water/mud spring
(J-RAPID)
– Mostly scarf area of KV, central
part was less
• 1934 Bihar Earthquake
– 3 sites were clarified of water/mud
springs, they are central part of KV
(Rana’s black book)
New Findings
by New Survey
New findings of
Liquefaction
2015 Eq. (new 11)
1934 Eq. (new 3)
1934 might liquefy
more severely
than 2015

15. WN model
Western Nepal Eq.
The 2015 Gorkha Eq.
(Modification by x1/5)
CNS-1 Model
Central Nepal South Eq.
(Modification by x1/3)
PGA for Scenario Earthquakes
15
The 1934 Bihar-Nepal Eq.
(No Modification by x1/1)
CNS-2 Model
Central Nepal South Eq.
(Modification by x1/2)
CNS-3 Model
Central Nepal South Eq.
(Modification by X2/3)
150-200gals 150-200gals 200-400gals
250-400gals 250-600gals 300-800gals
Similar level
of Gorkha EQ
Only a few Some
Some more More
Few
Some

16. 16After Engineering, Environmental Geology Map by DMG, 1998
Slope failure history in Kathmandu Valley

17. Concept of earthquake induced slope failure
assessment method by Tanaka et al. (1980)
Tanaka (1980)’s equation
ac = g*(C/γ*h + (cosθ*tanφ- sinθ))
Where
ac: critical acceleration including the slide (PGA)
g: acceleration of gravity
C: cohesion of soil
φ：internal friction angle of the layer
γ: unit weight of soil
θ: angle of slope
h: thickness of the sliding layer
Failure of road along Bagmati River near
Khokana
caused by the 2015 Gorkha earthquake
(after KUKL)
Soil Properties are insufficient!
PGA, Soil Properties and slope
angle are fundamental factors

18. WN model
Western Nepal Eq.
The 2015 Gorkha Eq.
(Modification by x1/5)
CNS-1 Model
Central Nepal South Eq.
(Modification by x1/3)
PGA for Scenario Earthquakes
18
The 1934 Bihar-Nepal Eq.
(No Modification by x1/1)
CNS-2 Model
Central Nepal South Eq.
(Modification by x1/2)
CNS-3 Model
Central Nepal South Eq.
(Modification by X2/3)
150-200gals 200-400gals
250-400gals 250-600gals 300-800gals
Similar level
of Gorkha EQ
FewOnly a few Some
Some Some more More

19. 1. 2015 Gorkha Earthquake Records and Damage data provided
most important information.
2. Setting Scenario Earthquakes discussed with DMG as well as
through national and international experts comments.
3. Gorkha Earthquake brought Singular facts, many experts said
“Lucky”, in low input motion and soil non-linearity
4. This Project could provide remarkable Soil Modelling data:
1) Detailed Geomorphological map development
2) Geological cross section development provided structure and distribution
of geology and soils
3) Array Microtremor measurements provided dynamic properties such as
Vs structures of geological layers
4) Detailed modelling for 250mx250m of 11,934 grids, max depth ~550m
5. These results of PGA, PGV, MMI, Sa(T), Liquefaction,
Earthquake induced Slope Failure can be used for Seismic Risk
Assessment as well as Disaster Management Planning.
Output of Seismic Hazard Assessment

20. Some observations
• This Project focused KV, but Earthquakes affect not only KV.
At the same time, western portions, Terai and other regions shall be
affected and to be taken care of.
• Magnitude of Central Nepal South Scenario earthquake might be
overestimated. According to historical experiences, PGA due to the
cases of x1/1 or sometimes x2/3 would be overestimated.
• Insufficient data often provides rough, but more vulnerable output,
from disaster management point of views. Especially for liquefaction
and slope failure assumption in the Project.
• Some remaining issues are expected to be followed and enhanced by
SATREPS.
• Damage to buildings by Gorkha earthquake were affected some from
ground/soil condition, but mainly from building condition.
• Need more historical study, basic study and more resources!
• Thank you for your cooperation