変動地形からみた相模トラフにおけるプレート間地震サイクル

概要

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A tectonic geomorphological study is one of the best methods of evaluating the timing and the crustal deformation of pre-historic earthquake. To reveal the cycle of interplate earthquakes along the Sagami Trough, I investigatedthe emergedshoreline topography andthe fossilizedsessile assemblages in the Miura Peninsula andthe Boso Peninsula. The distribution pattern of coseismic vertical displacement during the 1703 Genroku Kanto Earthquake inferredfrom the height distribution of the paleo-shoreline suggests that the fault source model consists of a dual fault system of the Fault A andB. Fault A is also the source of the 1923 Taisho Kanto Earthquake. The geometry and ages of the emerged shoreline topography divided into several levels indicate that the characteristic earthquake generatedfrom Fault A has occurredabout every 400 years. One of several events, it is accompaniedwith a slip of Fault B, which has a recurrence interval of 2000-2700 years.