Seasonal modulation of seismicity in the Himalaya of Nepal

Laurent Bollinger, F. Perrier, J. P. Avouac, S. Sapkota, U. Gautam, D. R. Tiwari

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Abstract

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.

Original languageEnglish
Article numberL08304
JournalGeophysical Research Letters
Volume34
Issue number8
DOIs
Publication statusPublished - 28 Apr 2007

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    Bollinger, L., Perrier, F., Avouac, J. P., Sapkota, S., Gautam, U., & Tiwari, D. R. (2007). Seasonal modulation of seismicity in the Himalaya of Nepal. Geophysical Research Letters, 34(8), [L08304]. https://doi.org/10.1029/2006GL029192