2:45 PM - 3:00 PM
[SSS25-17] Simulation of long-period ground motions in the Kathmandu basin during the 2015 Gorkha, Nepal, earthquake
Keywords:Long-period ground motions, The 2015 Gorkha earthquake, The Kathmandu basin, Waveform simulation
The source process of the 2015 Gorkha earthquake was estimated by the fully Bayesian multiple-time-window source inversion (Kubo et al. 2016) with jointly using near-field waveforms, teleseismic waveforms, and geodetic data. The estimated seismic moment and maximum slip are 7.5×1020 Nm (Mw 7.9) and 7.3 m, respectively. The total source duration is approximately 50 s. The derived source model has a unilateral rupture towards east and a large slip area north of Kathmandu with the maximum slip.
The 1D deep subsurface velocity structure beneath KATNP was constructed by a trial-and-error process to reproduce the peak period on the long-period side of the horizontal-to-vertical spectral ratios of coda waves from eight aftershock recordings. The available geological and geophysical information were also utilized in this process. In this basin structure model, the thickness of low-velocity (Vs < 500 m/s) layers is approximately 460 m.
Using the derived source model of the 2015 Gorkha earthquake and the structure model of the Kathmandu basin, we carried out the simulation of the long-period ground motions during the 2015 Gorkha earthquake. The simulation demonstrated that the major features of the observed waveforms can be reproduced by our source and basin structure models.
[Acknowledgments] The high-rate GPS data provided by the Department of Mines and Geology, Tribhuvan University, and California Institute of Technology, and the strong motion data observed by the USGS were used in this study.