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Ground-motion scaling in the Kachchh Basin, India, deduced from aftershocks of the 2001 M (sub w) 7.6 Bhuj earthquake

Paul Bodin, Luca Malagnini and Aybige Akinci
Ground-motion scaling in the Kachchh Basin, India, deduced from aftershocks of the 2001 M (sub w) 7.6 Bhuj earthquake
Bulletin of the Seismological Society of America (October 2004) 94 (5): 1658-1669

Abstract

We studied the excitation, propagation, and site effects in the Kachchh basin of India by using ground-motion recordings from a temporary seismograph network deployed to study aftershocks of the M (sub w) 7.6 Bhuj earthquake of 26 January 2001. The Kachchh basin has been proposed as a useful analog region for studying hazard in other earthquake-prone but slowly deforming regions, such as the central United States. The earthquakes we studied ranged in size from about M 2 to M 5.2, and travel paths ranged from a few kilometers to about a hundred kilometers. There was a broad range of focal depths among the aftershocks, so the data were divided into two overlapping subsets to test the sensitivity of the derived propagation and source parameters to focal depth. Parameters we constrained include the source excitation terms (related to stress drop), a frequency-dependent attenuation operator, a geometric spreading function, and an operator to account for site effects. Our results indicate that seismic-wave attenuation in Kachchh crust is very low, similar to other continental intraplate areas such as central and eastern North America. We also estimated seismic moments and stress drops for the earthquakes by fitting single-corner-frequency source-model spectra to the observed spectra, corrected for propagation by using our derived parameters. Stress drops were found to scale with seismic moment and to be rather high overall. By using a stochastic point-source model to estimate mainshock ground motions, we found that the distance decay of expected peak ground motions, assuming a stress drop of 15-20 MPa, compare well with the scant observations for the Bhuj earthquake. Ground-motion predictions for Kachchh, based on Bhuj aftershock data, support the idea that the region may have similar hazard to proposed analog areas in North America.


ISSN: 0037-1106
EISSN: 1943-3573
Coden: BSSAAP
Serial Title: Bulletin of the Seismological Society of America
Serial Volume: 94
Serial Issue: 5
Title: Ground-motion scaling in the Kachchh Basin, India, deduced from aftershocks of the 2001 M (sub w) 7.6 Bhuj earthquake
Affiliation: University of Memphis, Center for Earthquake Research and Information, Memphis, TN, United States
Pages: 1658-1669
Published: 200410
Text Language: English
Publisher: Seismological Society of America, Berkeley, CA, United States
References: 31
Accession Number: 2005-011391
Categories: Seismology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables, sketch maps
N23°30'00" - N24°00'00", E70°00'00" - E71°00'00"
Secondary Affiliation: Istituto Nazionale di Geofisica e Vulcanologia, ITA, Italy
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute.
Update Code: 200505
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