Fully Coupled Modeling of Dynamic Rupture, Wedge Plasticity, and Tsunami for Great Earthquakes in the Japan Trench

San Diego State University Foundation, San Diego CA

Investigators

Abstract

The 2011 magnitude 9 Tohoku Japan earthquake is probably the world's best observed great earthquake, but in spite of this we still do not fully understand how it generated such a large and deadly tsunami. Dr. Ma and his student will use sophisticated computer models to test the idea that thick deposits of sand and clay on the seafloor can deform more in an earthquake than solid rock, leading to more change in elevation of the seafloor and a bigger tsunami. This could explain the huge tsunami wave along the Sanriku coast, north of where most of the Tohoku earthquake's energy was unleashed. The computer model will be tested using data from past tsunami-producing earthquakes in Japan, and will also be used to understand sound waves that are generated in the ocean when a tsunami begins. Sound waves travel through the ocean much faster than the tsunami wave itself, and can be used to improve the accuracy of tsunami warnings. Dr. Ma and his student will test a hypothesis that the large 2011 tsunami along the Sanriku coast was caused by inelastic wedge deformation north of 38.5°N in the Japan Trench due to presence of thick sediments, by developing a fully-coupled model of dynamic rupture, wedge plasticity, and tsunami for the 2011 Tohoku earthquake. The fully-coupled model ensures the most accurate excitations of ocean acoustic waves and tsunami. This three-year project will include the following activities: (i) developing a self-consistent dynamic rupture model of the 2011 Tohoku earthquake that can explain important geodetic, seismic, tsunami, and differential bathymetry observations. (ii) simulating the 1896 and 1933 Sanriku earthquakes by fully coupling dynamic rupture and tsunami and investigating the sensitivities of ocean acoustic waves and tsunami to shallow slip and wedge plasticity in these three earthquakes. (iii) identifying ocean acoustic waves that can be used for next-generation tsunami early warning systems due to megathrust and outer-rise normal-faulting earthquakes in the Japan Trench and worldwide. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.