Seismotectonics and seismogenesis of Mw7.8 Gorkha earthquake and its aftershocks

Arora, B. R. ; Bansal, B. K. ; Prajapati, Sanjay K. ; Sutar, Anup K. ; Nayak, Shailesh (2017) Seismotectonics and seismogenesis of Mw7.8 Gorkha earthquake and its aftershocks Journal of Asian Earth Sciences, 133 . pp. 2-11. ISSN 1367-9120

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The April 25, 2015, Mw7.8 Gorkha earthquake in central Nepal was followed by intense aftershock activity, including Mw6.7 shock on April 26, 2015 and Mw7.3 shock on May 12, 2015. Synthesis of the focal mechanisms, space-time distribution of seismic activity in relation to previously imaged crustal velocity and resistivity structures reveals focusing of the Mw7.8 Gorkha earthquake near the upper surface of the thin fluid-filled low velocity and high conducting layer immediately above the plane of the detachment. On the geophysical sections, the detachment is identified as a sharp positive velocity interface. Modulation of frictional coupling and mechanical weakening by high-pore pressure fluids counteract the arc-normal stresses creating conditions for failure and nucleation of the Gorkha earthquakes on a plane sub-parallel with the detachment. Spatio-temporal patterns in aftershock activity indicate rapid alteration of main shock-induced stress fields, triggering a strong aftershock of Mw6.7. Large stress drop and increased energy released by the Mw6.7 event facilitates upward injection of high pore-pressure fluid fluxes into the hidden out-of-sequence thrust. It is suggested that decrease in shear strength along the hidden thrust plane due to the diffusion of high pore pressure fluids created conditions favorable to trigger Mw7.3 aftershock.

Item Type:Article
Source:Copyright of this article belongs to Elsevier Science.
Keywords:Gorkha Earthquake; Himalayan Seismicity; Detachment; Fluid Dynamics; Transient Stress Transfer; Triggered Aftershocks
ID Code:103601
Deposited On:01 Feb 2018 11:27
Last Modified:01 Feb 2018 11:27

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