Verification of Sub-Faults Division in the Numerical Evaluation Precision of Near-Fault Seismic Ground Motions Accompanied by Surface Rupture

Date: 4/26/2019

Time: 06:00 PM

Room: Fifth Avenue

Numerical evaluation of near-fault ground motions is of great interest to many earthquake engineers, because the pulse-like ground motions and accompanied surface ruptures are responsible to structure damages in many historic earthquakes. However, in order to estimate amplitudes and spatial variation of near-fault pulse-like ground motions with high precision, the calibration of numerical evaluation methods is indispensable. In this study, as a case study, we applied the seismic fault model of the main shock of the 2016 Kumamoto, Japan, earthquake, to investigate the influence of sub-fault division in the fault plane to evaluat the near-fault strong ground motions. During the 2016 Kumamoto earthquake, surface ruptures along the seismic fault and large-amplitude pulse-like waves with predominant period of 1 second were observed in the vicinity of the seismic fault. These near-fault pulse-like ground motions resulted in devastating damages to wooden houses. For the numerical simulation of ground motions near the seismic fault accompanied by surface ruptures, evaluation of the Green's function is crucial as well as the subsurface structure. We performed a theoretical simulation of the near-fault seismic ground motions, which considered a fine division of the fault plane into several sub faults. Numerical convergence of the spatial integration is examined using the Thin Layer Method, which is addressed as a numerically effective tool for ground motions simulation for the seismic fault with surface ruptures. We found that the permanent displacement and dynamic velocity converge can be well produced using an integration spacing of approximately half of the source distance based on the comparison with results of the rigorous methods. We applied the seismic fault model to the main shock of the 2016 Kumamoto earthquake to investigate the influence of differently divided sub-faults in the fault plane on the evaluation of strong ground motions in the vicinity of the seismic fault.

Presenting Author: Masayuki Nagano

Authors