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Seasonal modulation of seismicity in the Himalaya of Nepal

Bollinger, L. and Perrier, F. and Avouac, J.-P. and Sapkota, S. and Gautam, U. and Tiwari, D. R. (2007) Seasonal modulation of seismicity in the Himalaya of Nepal. Geophysical Research Letters, 34 (8). Art. No. L08304. ISSN 0094-8276.

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For the period 1995–2000, the Nepal seismic network recorded 37 ± 8% fewer earthquakes in the summer than in the winter; for local magnitudes ML > 2 to ML > 4 the percentage increases from 31% to 63% respectively. We show the probability of observing this by chance is less than 1%. We find that most surface loading phenomena are either too small, or have the wrong polarity to enhance winter seismicity. We consider enhanced Coulomb failure caused by a pore-pressure increase at seismogenic depths as a possible mechanism. For this to enhance winter seismicity, however, we find that fluid diffusion following surface hydraulic loading would need to be associated with a six-month phase lag, which we consider to be possible, though unlikely. We favor instead the suppression of summer seismicity caused by stress-loading accompanying monsoon rains in the Ganges and northern India, a mechanism that is discussed in a companion article.

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Additional Information:© 2007 American Geophysical Union. Received 22 December 2006; revised 26 February 2007; accepted 19 March 2007; published 26 April 2007. We are most grateful to R. Bilham for his comments and suggestions which greatly helped improving the scientific content and presentation of this manuscript. K. Heki also provided very useful criticisms and suggestions. We thank the teams of DMG and DASE who have contributed to the installation and maintenance of the stations and routine processing of the seismic data. This is IPGP contribution number 2222. This study benefited from support and thoughtful discussions with P. Tapponnier, G. King and M. R. Pandey.
Group:Caltech Tectonics Observatory, Caltech Tectonics Observatory. Indo-Asian Collision Zone, Seismological Laboratory
Subject Keywords:earthquakes; Himalaya; hydroseismicity
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Caltech Tectonics Observatory142
Record Number:CaltechAUTHORS:20101115-115352564
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Official Citation:Bollinger, L., F. Perrier, J.-P. Avouac, S. Sapkota, U. Gautam, and D. R. Tiwari (2007), Seasonal modulation of seismicity in the Himalaya of Nepal, Geophys. Res. Lett., 34, L08304, doi:10.1029/2006GL029192
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:20811
Deposited By: Tony Diaz
Deposited On:15 Nov 2010 22:54
Last Modified:11 Jun 2015 13:57

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