Kinematic and dynamic rupture process of the 2015 Nepal Mw 7.8 earthquake

Abstract:

On April 25 2015 a devastating Mw 7.8 earthquake occurred in Nepal and killed about 9000 people. This event is a typical low dip angle thrust event due to the collision and convergence between the Indian and Eurasian plate in the Himalayan arc since the last 1934 Mw 8.1 event. With the help of modern geophysical instrumental observation, such as seismic wave recordings, GPS and InSAR, the rupture process of this event can be well investigated. We use compressive sensing (CS) method to invert the coseismic radiation of this event in different frequency bands. Our CS results indicate an east-southeastward unilateral rupture process with frequency-dependent properties similar to that in oceanic subduction zone. This frequency-dependence and the seimogenic mechanism of this event are derived from the down-dip varied frictional properties in the Main Himalayan thrust (MHT). In the meanwhile, various observations indicate that the rupture of this event does not reach the ground surface and the shallow stick-slip portion of MHT is still locked, this is different from the 2008 Wenchuan event. To investigate why the rupture stops and does not reach the ground surface, we use numerical method to simulate the influence of high ground topography and fault geometry on the propagation of the rupture. Through combining the results from geophysical observation and numerical simulation, we can better understand the regional tectonic and estimate the potential seismic hazard in the active Himalayan arc.