Wedge Inelasticity and Fully Coupled Models of Dynamic Rupture, Ocean Acoustic Waves, and Tsunami in the Japan Trench: 1. The 2011 Tohoku-Oki Earthquake

Yue Du, & Shuo Ma

Published September 8, 2024, SCEC Contribution #13652, 2024 SCEC Annual Meeting Poster #119

Along-strike variation of sediment thickness and inelastic wedge deformation can significantly affect the along-strike variation of near-trench slip, seismic radiation, and tsunamigenesis in the Japan Trench. We present fully coupled models of dynamic rupture, ocean acoustic waves, and tsunami for large tsunamigenic earthquakes in this subduction zone, to investigate the full physics of tsunami generation. In part 1, we focus on the 2011 Mw 9.1 Tohoku-Oki earthquake. Part 2 addresses the 1896 Sanriku earthquake. We extend a dynamic rupture model of the 2011 Tohoku-Oki earthquake (Ma, 2023) by including a compressible ocean. The fully coupled models produce tsunami in good agreement with those from a dispersive shallow-water model, confirming the validity of both models. We show strong radiation of ocean acoustic and seismic waves caused by the fast rupture velocity and large near-trench slip south of 39°N, dominated by elastic wedge response. However, in the northern Japan Trench (north of 39°N) where sediment thickens, the inelastic wedge deformation excites tsunami efficiently with diminishing near-trench slip (<20 m, consistent with the differential bathymetry observations) and slow rupture velocity (~850 m/s), which causes significantly weaker radiation of ocean acoustic and seismic waves. These results highlight the importance of physics of tsunami generation in tsunami hazard assessment revealed by weak radiation and may pose the challenge of potential use of ocean acoustic waves for tsunami early warning.

Key Words
Tsunami Generation

Citation
Du, Y., & Ma, S. (2024, 09). Wedge Inelasticity and Fully Coupled Models of Dynamic Rupture, Ocean Acoustic Waves, and Tsunami in the Japan Trench: 1. The 2011 Tohoku-Oki Earthquake. Poster Presentation at 2024 SCEC Annual Meeting.

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