Dynamic Rupture Models of the 2015 Mw7.8 Nepal Earthquake

Yongfei Wang, Steven M. Day, & Marine A. Denolle

Submitted August 14, 2017, SCEC Contribution #7675, 2017 SCEC Annual Meeting Poster #171 (PDF)

The April 15th, 2015 Mw 7.8 Gorkha earthquake in Nepal occurred on a very shallowly dipping Main Himalayan Thrust (MHT) fault, where local fault geometry and proximity of the free surface will introduce asymmetry of stress and strain fields across the fault. Dynamic rupture simulations of the Gorka earthquake yield earthquake parameters comparable to those deduced from kinematic inversions, including seismic moment, static stress drop and rupture velocity. Pulse-like rupture characteristics have been inferred in some source inversion studies, and the dynamic rupture simulations reproduce this behavior, predicting pulse widths in agreement with observations, and supporting an interpretation in which this pulse-like rupture is principally controlled by fault geometry. This is further supported by near field high-rate GPS station (KKN4) recordings. The unfiltered recorded GPS time series are remarkably similar to the synthetic ground velocity predicted by our rupture dynamic model, including its pulse width, amplitude and pulse shape. That record also constrains the updip extent of rupture and limits the admissible range of parameters governing co-seismic inelastic deformation adjacent to the rupture. Dynamic simulations also suggest that multistage processes indicated by some back-projection imaging may be related to a hypocentral location on a steep ramp lying downdip from the main, shallow-dipping rupture surface. The simulations also reveal the role of reflected seismic waves from the free surface in generating time-dependent normal stresses on the fault, with potentially significant effects on both rupture propagation and slip.

Citation
Wang, Y., Day, S. M., & Denolle, M. A. (2017, 08). Dynamic Rupture Models of the 2015 Mw7.8 Nepal Earthquake. Poster Presentation at 2017 SCEC Annual Meeting.


Related Projects & Working Groups
Fault and Rupture Mechanics (FARM)