Rupture process of the 2015 Mw7.9 Nepal earthquake from the joint inversion

Abstract:

The 25 April 2015 earthquake (Mw7.9) struck Nepal near the middle segment of Himalaya. Large earthquakes occurred around this region frequently in history. The rupture process could help us to investigate the characters of the disaster earthquakes. For this event many kinds of observation data could be used to constrain the rupture process. Data of some 1Hz GPS stations of the China Crustal Movement Observation Network were processed by the software GAMIT and we obtained the waveforms of this earthquake. The waveforms of several 5Hz GPS stations near the epicenter were provided by the Jet Propulsion Laboratory (JPL) (http://aria-share.jpl.nasa.gov/events/20150425-Nepal_EQ/GPS/). The ALOS-2 satellite, operated by the Japanese Space Agency, collected a useful of L-band InSAR data and Lindsey et al. determined the coseismic displacement of the line-of-sight (http://topex.ucsd.edu/nepal/). We resampled the coseismic displacement of Lindsey et al. to constrain the rupture process. In addition teleseismic broadband body waves, long period surface waves, waveforms of one regional broadband station and one local strong motion station were combined in the joint inversion. The epicenter of United States Geological Survey (USGS) and the mechanism of Global Centroid Moment Tensor (GCMT) were applied. The Mw 7.9 earthquake ruptured a thrust fault orienting 293^o and dipping 7^o to the NE, locating near the middle segment of Himalaya. This earthquake was a unilateral event and the rupture of asperity mainly propagates to the southeast, spanning a depth range from 8 km to 18 km. The inverted slip distribution is dominated by a rectangle shape slip patch with the length of ~120km. The weighted rupture velocity is about 2.1 km/s and the total seismic moment is about 8.6x10²⁰ Nm. The imaged fault slip correlates well with the aftershock distribution.