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Structural Control of 2015 Mw 7.8 Gorkha Rupture

Session: Exploring Rupture Dynamics and Seismic Wave Propagation Along Complex Fault Systems I

Type: Oral

Date: 4/19/2021

Presentation Time: 10:30 AM Pacific

Description: 

Rupture of Mw 7.8 Gorkha earthquakes is thought to be unilateral and relatively simple. Starting at the hypocenter, it propagates unilaterally eastward to unzip about 150 km alongstrike the Main Himalayan Thrust (MHT). We use four global seismic arrays and a local temporary dense seismic network to reveal the rupture dynamics and structural details of the rupture area. Our study shows that it is a relatively complex rupture controlled by intricate fault structures along MHT. Rupture started with unilateral ESE-ward propagation but bifurcated into two branches near the end. This is likely due to presence of a strong fault patch that eventually is broken after two weeks of the mainshock to produce the largest aftershock in this sequence – Mw 7.3 Kodari earthquake. Aftershock distribution obtained by the dense local NAMASTE network reveals a duplex structure that is responsible for generating the majority of the aftershocks to the east [Mendoza et al., 2019]. The western part is relatively quiet in terms of aftershock activity and appears to be structurally simple. Seismic tomography also shows lateral variations consistent with this interpretation. The rupture is arrested abruptly at its eastern end by well-defined structures that may mark alongstrike segment boundary in this area.

Presenting Author: Abhijit Ghosh

Student Presenter: No

Authors