Presentation on Seismic Hazard Assessment at 1st JICA ERAKV Project Seminar

1. 1
The project for Assessment of Earthquake Disaster Risk for the
Kathmandu valley in Nepal (ERAKV)
Seismic Hazard Assessment and Results
By
Mukunda Bhattarai
Seismologist
(NSC/DMG)
&
Fumio Kaneko
JICA Project Team
First Seminar, “Towards Resilient Kathmandu Valley”
September 16, 2016

2. 2
Contents
Schedule of seismic Hazard Assessment
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. Determined after taking into account of comments from Scientific Community 4
Three Scenario Earthquakes
(1) Far-Mid Western Nepal Eq., Magnitude = 8.6
(2) Western Nepal Eq., Magnitude = 7.8
(3) Central Nepal South Eq., Magnitude = 7.8
Two Verification Earthquakes
(a) Recurrence of the 1934 Bihar-Nepal earthquake, Magnitude = 8.3
(b) Recurrence of the 2015 Gorkha earthquake, Magnitude = 7.8, 7.3
KV
Setting of Scenario Earthquakes

5. 5
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)

6. 6
Scenario Earthquake Fault Model (2002)
Three Scenario Earthquakes and One Verification Earthquakes
(different from 2015 Gorkha earthquake)

7. 7
Final-slip distribution of Gorkha earthquale
2015 Gorkha earthquake
is different from
2002 Scenario earthquakes,
Mid Nepal
Earthquake
North Bagmati
Earthquake

8. 8
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
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)
Development of Ground Model

9. 9
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.
Contd…

10. 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
10

11. Reflecting surface geology and topography
derived from sedimentary environment 11
Based on
1:15,000 aero photos
Contd…
Geomorphological Map

12. Ground softness
Map (AVS30)
Liquefaction
Susceptibility Map
Slope Failure
Susceptibility Map
12
Seismic zoning Maps Development
easy to grasp rough sketch of ground nature

13. 13
Chandragiri fault is “active” or not?
Tectonic Structure in Kathmandu Valley
If active, If generate earthquake, what will happen?
Serious condition for Kathmandu.

14. • Setting target area and grid size
• Setting depth of bedrock distribution (gravity exploration and
drilling)
• Compiling sub-surface ground layers,
• Setting their composition and structure (geomorphological
map, geological cross sections etc.)
• Surveying Vs value for sub-surface ground layers ( In this
project by microtremor measurement)
• Adjusting Vs values for each ground layers
• Setting ground model (soil column) with numerical values
• Modelling factors are Vs, density, width etc. for earthquake
response calculation 14
Ground Modelling
for Seismic Hazard Assessment

15. 15
Rock depth contour
by gravity anomaly
Rock Surface contour
Rock Depth and Rock Surface Contour
Bed rock surface shape
is originally
mountainous area?

16. Geological Cross Section Development
G-line
E-line
F-line
16
Lines1-11
A – N lines
ERAKV 4th JCC WG1 2016/09/14Produced by this project
from geological map,
drilling data etc.
for 25 sections
with interval 2km
Rock surface and layer
distribution are
not simple
Many outcrops
Kirtipur, Pashupatinath,
Swayanbu,
hidden ridge
at Lalitpur etc.

17. 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

18. 18
Array Microtremor sites for Vs structure

19. Setting Vs structure of Geological Layer
Vs structure for Sub-surface
layers are given from the
developed relations based on
the results of L-shape
Microtremor Measurement
and Geomorphological units.
19
AM01 AM02 AM03 AM04 AM05
(TU) (IoE) (Thimi) (Tundikhel) (Manohara)
0 f 0 vp 200 0 Th 200 0 vp 170 0 al
180 11 klm 15 klm
20 klm 25 klm 28 lkl
36 klm 290
300 230 45 Tarebhir
50
77 lkl 230
87 Tarebhir 370 410
94 WR 520
103 lkl
119 lkl 116 Tarebhir
128 Tarebhir 130 Tarebhir
134 WR 610
420
390 400
230
250 WR 450
500 275
520
360 WR 580
454 WR 730
Geological
Layer
Vs (m/sec)
Kalimati 250 - 320
Tarebhir 400 - 500
Weathered
Rock
600
Determined by Triangle Array Microtremor Survey results with DMG

20. 20
Predominant Period of
Single Point Microtremor Measurement
Longer periods of
predominant period of ground
for central area

21. 21
0
1
2
0 1 2 3 4 5 6
QuaterWaveleng
Observed MT 1st Peak Period (sec)
dot line 1
dot line 2
solid line
0
1
2
3
4
5
6
0 1 2 3 4 5 6
TransferFunc.1stPeakPeriod(sec)
Observed MT 1st Peak Period (sec)
Comparison of 1st Peak Period between MT (1st)
and Ground Model (1st, transfer fuction)
ERAKV 1
ERAKV 2
Kukidome
Paudyal
ERAKV1 (Array)
dot line 1
dot line 2
solid line
0
1
2
3
4
5
6
0 1 2 3 4 5 6
TransferFunc.2ndPeakPeriod(sec)
Observed MT 1st Peak Period (sec)
Comparison of Peak Period between MT (1st) and
Ground Model (2nd, transfer fuction)
ERAKV 1
ERAKV 2
Kukidome
Paudyal
ERAKV1 (Array)
dot line 1
dot line 2
solid line
0
1
2
0
QuaterWaveleng
0
1
2
0 1 2 3 4 5 6
QuaterWaveleng
Observed MT 1st Peak Period (sec)
dot line 1
dot line 2
solid line
Tg by Single-Point Microtremor corresponding to
First peak, Second peak of Transfer function
by SH wave multi-reflection theory using ground models.
Predominant Period of
Single Point Microtremor Measurement
Showing 2 groups of longer period and shorter period

22. Predominant Period by ground model
22
Tg (first peak) of
Transfer function by SH wave multi reflection theory
0
1
2
3
4
5
0 1 2 3 4 5 6
QuaterWavelengthPeakPeriodatUpperWR
Observed MT 1st Peak Period (sec)
ERAKV 1
ERAKV 2
Kukidome
Paudyal
ERAKV1 (Array)
dot line 1
dot line 2
solid line
0
1
2
3
4
5
6
0 1 2 3 4 5 6
TransferFunc.1stPeakPeriod(sec) Observed MT 1st Peak Period (sec)
Comparison of 1st Peak Period between MT (1st)
and Ground Model (1st, transfer fuction)
ERAKV 1
ERAKV 2
Kukidome
Paudyal
ERAKV1 (Array)
dot line 1
dot line 2
solid line
2-4 seconds of
predominant period of ground
for central area
corresponding to first peak by ground model

23. 0
1
2
0 1 2 3 4 5 6
QuaterWavelen
Observed MT 1st Peak Period (sec)
dot line 1
dot line 2
solid line
0
1
2
3
4
5
6
0 1 2 3 4 5 6
TransferFunc.1stPeakPeriod(sec)
Observed MT 1st Peak Period (sec)
Comparison of 1st Peak Period between MT (1st)
and Ground Model (1st, transfer fuction)
ERAKV 1
ERAKV 2
Kukidome
Paudyal
ERAKV1 (Array)
dot line 1
dot line 2
solid line
0
1
2
3
4
5
6
0 1 2 3 4 5 6
TransferFunc.2ndPeakPeriod(sec)
Observed MT 1st Peak Period (sec)
Comparison of Peak Period between MT (1st) and
Ground Model (2nd, transfer fuction)
ERAKV 1
ERAKV 2
Kukidome
Paudyal
ERAKV1 (Array)
dot line 1
dot line 2
solid line
0
1
2
0 1 2 3 4 5 6
QuaterWavelen
Observed MT 1st Peak Period (sec)
dot line 1
dot line 2
solid line
Second Dominant Period by ground model
23
Tg (second peak) of
Transfer function by SH wave multi reflection theory
1-1.5 seconds of
predominant period of ground
for central area
corresponding to second peak by ground model

24. Ground Model Confirmation
24
0.1
1
10
100
0.1 1 10
H/V
Period(sec)
H/V of Earthquake Obs. at DMG
20150425
20150426
20150512
Average
0.1
1
10
0.1 1 10
H/V
Period (sec)
H/V Microtremor at DMG
0.1
1
10
100
0.1 1 10
FourierSpectralRatio
Period (sec)
DMG/PKI Fourier of Earthquakes
201505120705
20150512073709
Average
0.1
1
10
0.1 1 10
Amplification
Period (sec)
Amplification by Response Analysis
at DMG
Records are courtesy of DMG
first peakfirst peak second peaksecond peak

25. Development of Ground Model
25
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
S edim ent
K lm
Lkl
T arebhir
W R
Pashupatinath
Kirtipur
Lalitpur Madhyapur

26. 26
Attenuation Equations
(calculation of bedrock motion)
Since in Nepal strong motion attenuation equation has not been developed,
Among the numerous Attenuation Equations in the World,
New 4 equations of NGA (New Generation Attenuation by USGS) are selected.
Because NGA equations are popularly used in the world and
NGA equations can be utilized many regions of the world
with various parameters like fault type, ground condition etc.
Therefore, they can be applied to Nepal.
1) Abrahamson N. and W. Silva (2008)
2) Boore D. M. and G. M. Atkinson (2008)
3) Campbell K. W. and Y. Bozorgnia (2008)
4) Chiou B. S.-J. and R. R. Youngs (2008)

27. Recent 4 NGAAttenuation Relations
27

28. 28
Ground Model for Response Analysis for surface layers

29. Input motion at rock surface
(Kirtipur: main shock)
29
Ground surface
Rock surface

30. Amplification/Response of Ground
30
AVS30 (Average Vs)
Small Input
(amplification moderate)
Predominant Period
Large Input
(amplification singular)

31. Singularity of the Gorkha Earthquake
31
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

32. (Modification by x1/5) (Modification by x1/2)
The 2015 Gorkha Eq.
(No Modification by x1/1)
The largest aftershock of the
2015 Gorkha Eq.
(No Modification by x1/1)
The 1934 Bihar-Nepal Eq.
(No Modification by x1/1)
PGA for Verification Earthquakes (1)
32
Need no correction
Adjust to observed

33. 33
The 1934 Bihar-Nepal Eq.
(Modification by x1/2)
The 1934 Bihar-Nepal Eq.
(No Modification)
The 1934 Bihar-Nepal Eq.
(2002 project)
Year
Total
Buildings
Population Remarks
1833 7.3-7.7 3,565 29% 296 0.59% 12,500 50,000 Masonry
1934 8.4 55,739 71% 4,296 1.36% 78,750 315,000 Masonry
2015 7.8 91,150 15% 1,713 0.07% 614,777 2,517,023 RC+Masonry
2015 7.8 72,920 39% 1,370 0.18% 188,750 755,000 Masonry
Damage to
Buildings
Deaths
(references: Oldham(1883), Rana(1935), UNDP(1994), Bilham(1995, Web), NPC(2015),
Ohsumi(2015) , Sapkota(2016) and Bollinger(2016))
PGA for Verification Earthquakes (2)
Need no correction compared with actual Damage at the time
Tried x1/2 factor, but
Smaller than
actual damage level
due to 1934 EQ

34. PGA for Scenario Earthquakes
34
Far-Mid Western Nepal Eq.
No Modification by x1/1
Western Nepal Eq.
No Modification by x1/1
Central Nepal South Eq.
Case 1 : Modification by
x1/3
Central Nepal South Eq.
Case 2 : Modification by
x1/2
Central Nepal South Eq.
Case 3 : Modification by
X2/3
Central Nepal South Eq.
Case 4 : No Modification by
x1/1
Similar level of Gorkha EQ
PGA will be overestimated

35. Comparison of historical earthquake damage
in the Kathmandu Valley
35
1934 > 2015~1833 > 2015 largest aftershock
2015 Gorkha (M7.8) 50,984 (8.3%) 40,166 (6.5%) 1,713 (0.1%) 9,024 (0.4%) 614,777 2,517,023
Mid Nepal (M8.0) 53,465 (20.9%) 74,941 (29.3%) 17,695 (1.3%) 146,874 (10.6%)
North Bagmati (M6.0) 17,796 (6.9%) 28,345 (11.1%) 2,616 (0.2%) 21,913 (1.6%)
KV local (M5.7) 46,596 (18.2%) 68,820 (26.9%) 14,333 (1.0%) 119,066 (8.6%)
1934 Bihar (M8.4) 58,701 (22.9%) 77,773 (30.4%) 19,523 (1.4%) 162,041 (11.7%)
Damage of 2015 Gorkha earthquake Current
Scenario earthquakes and damage assessment of 2002 project At the time ot 2002
256,203 1,387,826
Earthquakes
Damage of Buildings Casualty No. of
Buildings
Population
Heavily Partly Death Injured
After JICA, 2002
Year
Total
Buildings
Population Remarks
1833 7.3-7.7 3,565 29% 296 0.59% 12,500 50,000 Masonry
1934 8.4 55,739 71% 4,296 1.36% 78,750 315,000 Masonry
2015 7.8 91,150 15% 1,713 0.07% 614,777 2,517,023 RC+Masonry
2015 7.8 72,920 39% 1,370 0.18% 188,750 755,000 Masonry
Damage to
Buildings
Deaths
(references: Oldham(1883), Rana(1935), UNDP(1994), Bilham(1995, Web), NPC(2015),
Ohsumi(2015) , Sapkota(2016) and Bollinger(2016))

36. Liquefaction history in the Kathmandu Valley
during 1934 and 2015 earthquakes
36
Liquefaction sites are locating in
Geomorphological units of al, vp, fr, nl
For 2015 EQ.
11 locations are
identified by
J-RAPID, but
are small scale
and most area
Not-liquefied.

37. 37
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

38. Liquefaction assumption result for
verification earthquakes (rainy season)
2015Gorkha EQ Largest Aftershock
of 2015Gorkha EQ
1934 Bihar-Nepal EQ
1 Bagmati River drainage (South of Chobar) Distance from River Dry Season Rainy Season
2 lower than 1290m (Valley central) a. within 250m 1m 0m
3 1290-1295m (Valley central) b. 250m - 500m 3m 2m
4 1295-1305m (Valley central) c. More than 500m 5m 4m
5 1305-1325m (Valley central)
6 higher than 1325m (Valley central)
al Alluvial Low land (O)
fr Former River Course (L)
nl Natural Levee (M)
vp Valley Plain (H)
Area Division Ground Water Level
High possibility
Geomorphology Judgment of Liquefaction Possibility
No possibility
Low possibility
Moderate possibility
38
Soil Properties are insufficient and they are assumed!
Only a few
None
Some

39. Far-Mid Western Nepal Scenario EQ Western Nepal Scenario EQ Central Nepal South Scenario EQ
(x1/3)
Central Nepal South Scenario EQ
(x1/2)
Central Nepal South Scenario EQ
(x2/3)
Central Nepal South Scenario EQ
(x1/1)
Liquefaction assumption result
for Scenario earthquakes (rainy season)
39
Soil Properties are insufficient and they are assumed!
Only a fewNone Some
Some more More Much
Similar level of Gorkha EQ

40. 40After Engineering, Environmental Geology Map by DMG, 1998
Slope failure history in Kathmandu Valley

41. 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

42. Earthquake induced slope failure assumption
result for verification earthquakes
Gorkha EQ
Largest aftershock
of Gorkha EQ
1934 Bihar-Nepal EQ
42
Soil Properties are insufficient and they are assumed!
Only a few None
Some

43. Far-Mid Western Nepal
Scenario EQ
Western Nepal
Scenario EQ
Central Nepal South
Scenario EQ (x1/3)
Central Nepal South
Scenario EQ (x1/2)
Central Nepal South
Scenario EQ (x2/3)
Central Nepal South
Scenario EQ (x1/1)
Earthquake induced slope failure assessment result for scenario earthquakes
43
Soil Properties are insufficient and they are assumed!
Only a fewNone Some
Some more More Much
Similar level of Gorkha EQ

44. 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

45. 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 would 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