Numerical Simulation of Pulse-Like Ground Motions During the 2011 Tohoku Earthquake

Session: What Can We Infer About the Earthquake Source Through Analyses of Strong Ground Motion? [Poster]
Type: Poster
Date: 4/29/2020
Time: 08:00 AM
Room: Ballroom
Description: 

One of the important characteristics of the strong ground motions during the 2011 Tohoku earthquake (Mw9.0) was that pulse-like strong ground motions with a time width of approximately 1 - 2 s were observed in the near-fault regions, especially in Miyagi Prefecture (Nozu, 2012; Nozu et al., 2012; Irikura and Kurahashi, 2013). The short time constants associated with these pulses indicate that those pulses were generated, not from so-called SMGAs with dimensions of several tens of kilometers but from SPGAs (Nozu et al., 2012) with dimensions of several kilometers. The author already developed a source model that can explain the ground motions including those pulses (Nozu, 2012; Nozu et al., 2012). By the way, the 2011 earthquake was not the first case in which pulse-like ground motions were observed during a large subduction earthquake. For example, during the 1978 Miyagi-ken-oki earthquake (Mw7.6), pulse-like ground motions were observed. Two source models were independently developed to explain those pulses by Matsushima and Kawase (2006) and Nozu et al. (2006); the former used numerical Green’s functions for a layered half space and the latter used corrected empirical Green’s functions (Kowada et al., 1998; Nozu et al., 2006). The two models were fairly consistent with each other in spite of the difference of the Green’s functions. On the other hand, in the author’s modelling of the 2011 earthquake, the corrected empirical Green’s function method was solely used. If another study aiming at modelling the pulse-like ground motions based on numerical Green’s functions is available for the 2011 earthquake, it could be more compelling to the users of numerical schemes. Therefore, in this study, a numerical modelling of the pulse-like ground motions during the 2011 Tohoku earthquake was conducted and the resultant source model was compared to the source model based on the corrected empirical Green’s function method. In conclusion, the pulse-like ground motions can be reproduced in a numerical scheme with a source model that involves a strong SPGA off Miyagi prefecture.

Presenting Author: Atsushi Nozu

Authors