It has been ten years since the Tohoku-oki earthquake occurred. Although this earthquake has caused a huge disaster to the entire country, the lessons learned from the earthquake have taught us what a scientific community needs to do to prepare for the next big earthquake. Various observations and data analyses immediately after the earthquake revealed that the cause of the giant tsunami was the huge fault slip of 50 m in the shallow part of the Japan Trench. Marine geophysical and geological studies on the Tohoku-oki earthquake over the past about ten years have provided new insights into the slip behavior of plate boundary faults and unresolved problems as follows: 1) is large shallow trench slip ubiquitously occurring spatially and temporally across the entire Japan Trench? 2) what are the factors that determine giant fault sliding? 3) what is a source process to generate a huge tsunami? 4) what are the effects of the large shallow megathrust earthquake on earthquake activity in the outer trench-slope? 5)what does fault slip behavior indicate before and after the earthquake? An essential approach to solving the problems raised by the Tohoku-oki earthquake is to capture an entire process before, during, and after a large earthquake. We believe the Nankai Trough is one of the most appropriate sites for addressing the unsolved questions above because the probability of the next M8-class earthquake there is remarkably high. Therefore, we are conducting a project in the Nankai Trough to model the behavior of fault slip by a realistic seismogenic zone model and continuously monitoring seafloor deformation with before, during, and after the earthquake. In this webinar, I will talk about the nature of large shallow plate boundary slip, unresolved issues of the Tohoku-oki earthquake revealed by the 10-year marine geophysical and geological studies, and the projects currently underway in the Nankai Trough based on the lessons learned from the earthquake.

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SZ4D presents International Webinars, a series where the working groups invite international scientists to present on different topics relevant to their research and region. SZ4D values international voices and invites you to learn from these folks.