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Linking Strong Ground Motions and Coseismic Landsliding Associated With the 25 April 2015 Mw 7.8 Gorkha Earthquake

Session: Physics-Based Earthquake Rupture Modeling and Strong Motion Simulations II

Type: Oral

Date: 4/23/2021

Presentation Time: 02:15 PM Pacific

Description: 

The Mw 7.8 Gorkha earthquake occurred on April 25, 2015 ~80km NW of Kathmandu, Nepal. The rupture was unilateral towards the southeast, unzipping the downdip edge of the locked zone of the Main Himalaya Thrust. Much of the damage and loss of life associated with this event was caused by coseismic landslides and related flooding events. Directly after the Gorkha 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. 25,000 individual landslides were mapped, many of which failed at ridge tops presumably due to a combination of steep topography and seismic wave amplification. Yet, a lack of seismic instrumentation in the rugged terrain of this region has made it difficult to establish relationships between the characteristics of ground shaking and the distribution of landslides. In this study, we investigate these relationships using seismic wavefield simulations of the Mw 7.8 Gorkha earthquake with a focus on understanding the influence of topography on ground shaking. Using the SPECFEM3D software package, kinematic models of the Gorkha earthquake are simulated within meshes that include a topographically complex and a smoothed Earth surface. The comparison from these two models allows us to isolate the effects of topography on the seismic wavefield, with preliminary results showing that ridgetop amplification of seismic ground shaking plays an important role on the occurrence of landsliding throughout the rupture area. 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

Student Presenter: Yes

Authors