Abstract
The assessment of local site effects on seismic ground motions is of great
importance in earthquake engineering practice. Several destructive earthquakes in the past
have demonstrated that the amplification of ground motion and associated damage to
structures due to local site conditions is a significant consideration in earthquake hazard
analysis. A recent paper published in this journal highlights the hazard posed by earthquakes
in the megacity of Kolkata in India due to its seismic and geological settings. The
seismic hazard assessment study speculates that the deep alluvial deposit in the city may
increase the seismic hazard probably due to the amplification of the seismic energies. This
paper focuses on the seismic response studies of the various soil strata (i.e. for local
subsurface conditions) obtained from various construction sites in the city for predicted
earthquake. It is very well recognized that site response studies (a part of seismic
microhazard zonation for urban areas) are the first step towards performance-based
foundation design or seismic risk analysis and mitigation strategy. One of the problems for
carrying out site-specific study in Kolkata is the lack of recorded strong motion data in the
city. Hence, this paper outlines a methodology to carry out site-specific study, where no
strong motion data or seismic data are available. The methodology uses wavelet-based
spectrum compatibility approach to generate synthetic earthquake motions and equivalent
linear method for seismic site response analysis. The Mega City of Kolkata has been
considered to explain the methodology. Seismic hazard zonation map by the Bureau of
Indian Standards classifies the City of Kolkata as moderate seismic zone (Zone III) with a
zone factor 0.16. On the other hand, GSHAP(Global Seismic Hazard Assessment Program)
map which is based on 10% probability of exceedance in 50 years specifies a maximum
peak ground acceleration (PGA) of 1.6 m/s2 (0.163 g) for this region. In the present study,
the seismic response has been carried out based on GSHAP. The results of the analysis indicate the amplification of ground motion in the range of 4.46–4.82 with the fundamental
period ranging from 0.81 to 1.17 s. Furthermore, the maximum spectral accelerations vary
in the range of 0.78–0.95 g.
Translated title of the contribution | Site-specific earthquake response study for hazard assessment in Kolkata city, India |
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Original language | English |
Number of pages | 23 |
Journal | Natural Hazards |
DOIs | |
Publication status | Published - 2011 |