HR: 14:15h
AN: T33F-03    [Abstracts]
TI: Seasonal variations of seismicity and geodetic strain in the Himalaya induced by surface hydrology as revealed from GPS monitoring, seismic monitoring and GRACE measurements
AU: Bettinelli, P
EM: pierre.bettinelli@cea.fr
AF: Laboratoire de Detection et de Geophysique, CEA, BP 12, Bruyeres-le-Chatel, 91680, France
AU: * Avouac, J
EM: avouac@gps.caltech.edu
AF: California Institute of Technology - Tectonics Observatory, 1200 E. California Blvd. MC 100- 23, Pasadena, CA 91125, United States
AU: Flouzat, M
EM: mireille.flouzat@cea.fr
AF: Laboratoire de Detection et de Geophysique, CEA, BP 12, Bruyeres-le-Chatel, 91680, France
AU: Bollinger, L
EM: laurent.bollinger@cea.fr
AF: Laboratoire de Detection et de Geophysique, CEA, BP 12, Bruyeres-le-Chatel, 91680, France
AU: Ramillien, G
EM: Ramillie@notos.cst.cnes.fr
AF: LEGOS, UMR 5566 CNRS/CNES/IRD/SHOM/UPS, 14, Avenue Edouard Beli, Toulouse, 31400, France
AU: Rajaure, S
EM: sudhir@seismonepal.gov.np
AF: National Seismological Centre, Department of Mines and Geology, Lainchaur, Kathmandu, Nepal
AU: Sapkota, S
EM: nscdmg@mos.com.np
AF: National Seismological Centre, Department of Mines and Geology, Lainchaur, Kathmandu, Nepal
AB: GPS measurements across the Nepal Himalaya of central Nepal show that long term secular shortening across the range is modulated by seasonal strain variations. Comparison with GRACE measurements of surface load variations and Topex-Poseidon measurements of free surface water elevation of major rivers in the Gangetic plain suggests that the strain variations are probably induced by seasonal variations of surface water storage. Comparison with local seismicity shows that geodetic strain variations also correlate with seasonal variations of seismicity: the seismicity rate is indeed twice as high in the winter as in the summer, and correlates with stress rate variations determined from the modeling of the GPS measurements. This observation provides a way to gauge secular stress build up. We infer ~10-20kPa/yr interseismic stress buildup within the seismicity cluster along the high Himalaya front. Given that Earth tides exert little influence on Himalayan seismicity, the correlated seasonal variation of stress and seismicity indicates that the duration of earthquake nucleation in the Himalaya is of the order of days to month, placing constraints on faults friction laws. The unusual sensitivity of seismicity to small stress changes in the Himalaya might be due to high pore pressure at seismogenic depth.
DE: 1217 Time variable gravity (7223, 7230)
DE: 1242 Seismic cycle related deformations (6924, 7209, 7223, 7230)
DE: 8123 Dynamics: seismotectonics
SC: Tectonophysics [T]
MN: 2007 Fall Meeting