Dynamic Triggering and fault geometry in the Central Himalaya Seismic Gap

Manuel M. Mendoza, Abhijit Ghosh, & S S. Rai

Submitted August 15, 2016, SCEC Contribution #6968, 2016 SCEC Annual Meeting Poster #248

The devastating Mw 7.8 Gorkha earthquake in Nepal on 25 April 2015, reawakened attention to the high earthquake risk along the Himalayan arc. As a result of the Gorkha event, it is important to identify where stresses are building up along and near the Main Frontal Thrust that could produce the next devastating earthquake in this area. The “central Himalaya seismic gap” is located in Uttarakhand, India, west of the Gorkha rupture area, where a large (> Mw 7.0) earthquake has not occurred for over the last 200 years [Rajendran, C.P., & Rajendran, K., 2005]. This 500 - 800 km long along-strike unruptured segment of Himalaya is poorly studied mainly due to the lack of modern and dense instrumentations. Here, we analyze a rich seismic dataset from a dense seismic network consisting of 50 broadband stations, that operated between 2005 and 2012. We develop a robust earthquake catalog of ~ 4,000 local events containing precise locations, and magnitudes. By refining those locations in HypoDD to form a tighter cluster of events using relative relocation, we illustrate the fault geometry in this region with high resolution. Furthermore, we observe periods of dramatic increases in local micro-seismicity dynamically triggered by remote, large teleseismic events. Generating a complete and consistent earthquake catalog not only sheds new light on the physical processes controlling the earthquake cycle in this locked segment of Himalaya, it also illustrates how stress is transferred along and between faults, whether via a static or dynamic mechanism. From this catalog, we aim to reveal fault structure, study seismicity patterns, and assess the potential seismic hazard in the central Himalaya seismic gap, and the surrounding region.

Mendoza, M. M., Ghosh, A., & Rai, S. S. (2016, 08). Dynamic Triggering and fault geometry in the Central Himalaya Seismic Gap. Poster Presentation at 2016 SCEC Annual Meeting.

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