Seismic noise based ground motion: strong shaking predicted in Tokyo for the next M7+ earthquake on the Itoigawa-Shizuoka tectonic line.

Marine A. Denolle, Pierre Boué, Gregory C. Beroza, & Naoshi Hirata

Submitted August 14, 2017, SCEC Contribution #7601, 2017 SCEC Annual Meeting Poster #269

The Itoigawa-Shizuoka Tectonic Line (ISTL) is a major oblique left-lateral crustal fault able to host M7+ earthquake and that is at a mature stage of its cycle. Its proximity to the Kanto sedimentary basin poses a threat to metropolitan Tokyo. This study constructs scenario earthquakes on the ISTL by predicting ground motions using the Virtual Earthquake Approach (Denolle et al, 2013, 2014), which uses the ambient seismic field to calculate the elastodynamic Green tensor between Hi-net stations, located above the ISTL that act as virtual sources, and MeSO-net stations, located in the Kanto Basin that act as receivers. By this approach we estimate ground motions from a suite of 270 kinematic sources and find that ground motions are high enough that unmodelled non-linear effects are likely. We also find that the shape of the sedimentary basin strongly affects the shaking by amplifying long period seismic waves, and that the vertical ground motions are more impacted than the horizontal ground motions as seismic waves are refracted by the basin edge. We quantify ground motion variability due to source uncertainty, surmise that ground motions are log-normally distributed with regard to source uncertainties, and suggest that this variability is overprinted (either enhanced or reduced) by the basin shape. Finally, we investigate the impact of source directivity in ground motions and find that instead of unilateral ruptures, certain epicentral location that generate bilateral ruptures produce twice as much shaking as other scenario earthquakes.

Key Words
seismic noise, ground motion, tokyo, dense arrays

Citation
Denolle, M. A., Boué, P., Beroza, G. C., & Hirata, N. (2017, 08). Seismic noise based ground motion: strong shaking predicted in Tokyo for the next M7+ earthquake on the Itoigawa-Shizuoka tectonic line.. Poster Presentation at 2017 SCEC Annual Meeting.


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