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Ground response analysis of Kathmandu valley
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SOIL/SITE RESPONSE IN KATHMANDU VALLEY
Dipendra Gautam
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OUTLINESIntroductionGeology of NepalGeology of Kathmandu ValleySeismicityResearch ObjectivesMethodologyResultsDiscussionsConclusionResearch HorizonAcknowledgements
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INTRODUCTION
Effects of Earthquakes:
Ground Shaking
Structural Hazards
Liquefaction
Landslides
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INTRODUCTION
Ground Shaking
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Source: www.google.com
INTRODUCTION
Structural hazard
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Source: www.google.com
INTRODUCTION
Liquefaction
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Source: www.google.com
INTRODUCTION
Landslide
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Source: www.google.com
INTRODUCTION
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Site Effects
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Amplitude r(t)= source signal e(t)* distance from source p(t)* local site effects s(t)
INTRODUCTION
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Seismic Hazard Map of Nepal ( After DMG)
Kathmandu
INTRODUCTION
Site Effects are important
1985 Mexico City earthquake (Mw=8.1) 1989 Loma Prieta earthquake (Mw=7.1)
NEPAL: An earthquake prone area…!
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GEOLOGY OF NEPAL
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Kathmandu
After Uprety and Le Fort, 1999
GEOLOGY OF KATHMANDU VALLEY
04/28/2023 12After DMG
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GEOLOGICAL CROSS SECTION OF KATHMANDU VALLEY
04/28/2023 13After Sakai, 2001
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SEISMICITY
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Rupture zones of large Himalayan earthquakes since 1800 (After Bilham et. al., 2001, modified by Feldl, 2005)
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SEISMICITY
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Intense micro-seismicity monitored between 1994 and 2005 ( after DMG, 2006)
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RESEARCH OBJECTIVES
Work out equivalent linear site response
analyses of soft sediment deposit of Kathmandu
valley
Comparison of computed parameters with the
damage pattern of 1934 Bihar-Nepal earthquake
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METHODOLOGY
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BOREHOLE LOCATIONS
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INPUT MOTION
(Uttarkashi earthquake) Time History
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Response spectra
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DATA ANALYSIS
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Boreholes: 53
Spatial variation
Depth of boring : 20 m to 30 m
Sediment deposit sites of
Kathmandu, Lalitpur and
Bhaktapur
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RESULTS
PEAK HORIZONTAL ACCELERATION
PEAK SPECTRAL ACCELERATION
AMPLIFICATION FACTOR
PREDOMINANT PERIOD
PEAK SPECTRAL VELOCITY
AVERAGE SHEAR WAVE VELOCITY
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RESPONSE OF SOIL
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Filling materials
Sandy silt
Medium to stiff clayey silt of low plasticity
30 m
Input motion: 6.9 Magnitude earthquake with epicentral distance of 34 km, PHA = 0.32 g
Surface: Amplified 7.788 times
Peak Horizontal Acceleration (g)
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BKTPATAN
THAMEL
Peak Spectral Acceleration (g)
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BKT
THAMEL
PATAN
Amplification factor
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Predominant period (s)
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THAMEL
BKTPATAN
Peak Spectral Velocity (cm/s)
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THAMEL
BKTPATAN
Avg. Shear Wave Velocity (m/s)
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DISCUSSION
Consistent results with the damage
pattern of 1934 Bihar-Nepal earthquake,
and the hazard map of JICA
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CONCLUSIONS
Results are consistent with the damage patterns of 1934 Bihar-Nepal earthquake
Higher amplification, higher peak spectral acceleration: Gokarna, and Kalimati Formation
Lower the shear wave velocity, lower is the amplification
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RESEARCH HORIZON
Development of Vs-N relationship for Kathmandu
valley
Assessment of signal attenuated at local site
Development of site specific design spectra using
‘NONLIN’
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04/28/2023 32
ACKNOWLEDGEMENTS
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04/28/2023 33
Thank you for your kind presence !!!
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