| Abstract |
Subduction earthquakes along plate-boundary megathrusts inflict a great natural hazard to humans by ground shaking and tsunamis. Seismological and geodetic observations made in the twenty-first century have revealed that slow earthquakes, an intermediate type of fault slip between fast rupture of regular earthquakes and stable sliding, frequently occurred at the updip and downdip ends of locked seismogenic zone. Repetition of slow earthquakes may cause an increased probability of subduction earthquakes and tsunamis. Despite the importance for understanding of subduction and slow earthquakes, actual conditions, dynamics, and underlying deformation mechanisms responsible for these earthquakes remained unknown, mainly caused by lack of geological observations, inaccessible for earthquake sources, and limited spatial resolution of geophysical information. However, the fault rocks exhumed from source depths of subduction and slow earthquakes, laboratory experiments using fault materials, and deep sea drilling have provided a window to examine seismogenic processes during subduction and slow earthquakes. In this seminar, I will show major progresses obtained by these geological approaches. In particular, I will focus on identification of past seismic slips from fault rocks, coseismic deformation and physical mechanisms, geological and rheological conditions of slow earthquakes, and estimation of earthquake source parameters (e.g., coseismic fault strength) through geological studies. |
