A study of local amplification effect of soil layers on ground motion in the Kathmandu Valley using microtremor analysis

Past researchers have anticipated the occurrence of a great earthquake in the central Himalayas in the near future.This may cause serious damage in the Kathmandu Valley,which sits on an ancient lake bed zone,with lacustrine sediments of more than 500 m depth.In this study,the predominant frequency o...

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Bibliographic Details
Published in:Earthquake Engineering and Engineering Vibration 2012-06, Vol.11 (2), p.257-268
Main Authors: Paudyal, Youb Raj, Yatabe, R., Bhandary, N. P., Dahal, R. K.
Format: Article
Language:English
Subjects:
Civil Engineering
Control
Dynamical Systems
Earth and Environmental Science
Earth Sciences
Earthquakes
frequency
resonance
Kathmandu
Freshwater
Geotechnical Engineering & Applied Earth Sciences
Ground motion
Lake beds
microtremor
predominant
Resonance
Seismic activity
Seismic engineering
Soil mechanics
Valley
Vibration
Vibration analysis
Water depth
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Summary:Past researchers have anticipated the occurrence of a great earthquake in the central Himalayas in the near future.This may cause serious damage in the Kathmandu Valley,which sits on an ancient lake bed zone,with lacustrine sediments of more than 500 m depth.In this study,the predominant frequency of ground motion is evaluated using the Horizontal-to-Vertical(H/V) spectral ratio technique and recordings of ambient noise.The results of the H/V ratio show two peaks in about 20 percent of the locations,which are distributed mainly in and around the center and northern part of the Kathmandu Valley.The predominant frequencies vary from 0.5 Hz to 8.9 Hz in the study area,whereas the second resonance frequency varies from 4 Hz to 6 Hz in the center and northern part of the valley.This indicates that the center and northern part of the valley have a wide range of resonance frequency due to two levels of impedance contrast one may be from the surface layer and the other may be from the layer underneath.These two levels of resonance indicate the importance of considering the effects of surface and lower layers during the planning and designing of infrastructures in the Kathmandu Valley.
ISSN:1671-3664
1993-503X
DOI:10.1007/s11803-012-0115-3