NEES
Poster
Marine Geophysical Survey of Tohoku Quake Rapture Zone
The 2011 Tohoku-oki earthquake is characterized by a huge tsunami which is proposed to be caused by a fault rupture that propagated to a shallow part of the subduction zone at the Japan Trench, on the basis of seismic wave, tsunami and …
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| Abstract |
The 2011 Tohoku-oki earthquake is characterized by a huge tsunami which is proposed to be caused by a fault rupture that propagated to a shallow part of the subduction zone at the Japan Trench, on the basis of seismic wave, tsunami and geodetic data. Those observations may indicate a possibility to rewrite a widely-accepted conceptual model of a subduction seismogenic zone which shows a shallow part of subduction zone is aseismic slip zone. However, as it was unclear how and where a co-seismic fault rupture extends near the trench by this earthquake, we still do not know if a plate boundary interface was slipped to the trench axis or a co-seismic slip propagated along a steeply dipping fault branching from the plate boundary at a landward slip near the trench. Here, we show a seismic image showing a co-seismic fault rapture extending all the way to the seafloor at the trench axis by comparing the seismic images acquired before and after the earthquake. This result provides a conclusive evidence showing that a shallow plate interface to the trench axis can be a seismic slip zone and that the slip to the trench along the plate boundary is a cause of a tsunami earthquake. |
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