Characterizing the Effect of Topography on Ground Shaking and Coseismic Landslides During the 25 April 2015 M7.8 Gorkha Earthquake in Nepal Through Full Wavefield Simulations

Session: Numerical Modeling of Rupture Dynamics, Earthquake Ground Motion and Seismic Noise
Type: Oral
Date: 4/29/2020
Time: 09:15 AM
Room: 230 + 235
Description: 

The Mw 7.8 2015 Gorkha earthquake occurred in Nepal on April 25, ~80km NW of the capital city of Kathmandu along the Main Himalaya Thrust (MHT). This event caused ~9000 fatalities, ~23,000 injuries and over a billion US dollars in damage directly from the earthquake and associated geohazards. Coseismic landslides, as well as flooding from landslide and glacial dammed lakes, are a major hazard for earthquakes that occur in regions of high elevation and high topographic relief such as the Himalaya. Directly after the earthquake, international efforts to characterize landslides and regions with high landslide potential were carried out in the form of field and satellite mapping of landslide source and deposition. Due to the lack of strong ground motion instrumentation in the region, this study seeks to simulate the seismic wavefield and combine this information with the high-quality landslide dataset to investigate relationships between various ground shaking parameters and the distribution of landslides in the Himalaya. We use SPECFEM3D to solve for the seismic wavefield of the Gorkha earthquake using an approximation of a finite fault model as the kinematic source in hexahedral meshes with both 1km resolution topography and smoothed topography. By relating the ground motion from the two simulations using an amplification factor, we isolate the effects of topography on the wavefield and compare this with the mapped landslide distribution, showing that ~70% of landslides occurred in a region with amplified shaking due to topography. The spatial relationships between simulated ground shaking and the distribution/intensity of landslides from the 2015 Gorkha earthquake will inform hazard evaluation for future events in this region.

Presenting Author: Audrey Dunham

Authors