Recurrence Time Intervals of Great Earthquakes in the Sagami Trough Region, Japan, as Deduced from Vertical Crustal Movement

Abstract

In the previous paper (SENO, 1977), the method of calculation of the recurrence time interval of great earthquakes in the Nankai and the Sagami trough regions was improved and refined. The recurrence time interval T and the value d (so-called recovery ratio) were estimated at the several sites on the seismic crustal movement areas along these troughs.
In the present paper, the vertical crustal movement observed by precise levellings and the defomation of the Holocene terraces in the south Kanto district are reexamined because the deformation of the coastal terraces have some complicated relations with the seismic crustal deformations in this region.
In the Shonan district, the deformation of the Holocene terraces is attributed to the crustal deformation associated with the 1923 Taisho type earthquakes and the recurrence time T of 180-400 years and the value d of 0.25-0.50 are obtained. In the southern Boso peninsula, the deformation of the Holocene terraces is divided into two: the crustal deformation associated with 1923 type earthquakes and that caused by the fault off the Boso peninsula which moved at the time of the 1703 Genroku earthquake. The recurrence time T and the value d for this fault off the Boso peninsula are estimated to be 950-2500 years and 0.20-0.54, respectively.