Suruga-Bay and Fujikawa Faults Probably Related to a Future“Tokai Earthquake”

Abstract

A new view on the mechanism of the occurrence of a future Tokai Earthquake is presented in this paper. Conventional hypothesis concerning the problem regards the Suruga Trough in the Tokai district of Central Japan as a subduction zone that juxtaposes the Phillippine Sea and Eurasian Plates. But the hypothesis does not appear to be sustained by full substantial evidence. Careful examination of submarine topography, seismic reflection profiles and magnetic data suggests that the Suruga-Bay fault along the Suruga Trough is not a plate boundary fault, but a great left-lateral strike-slip fault. Recently, an important fault named the Fujikawa fault was discovered in the land area. The fault strikes north and corresponds to the northern extension of the Suruga-Bay fault. The Fujikawa fault is the most active fault in Japan and has an average left-lateral slip of 3.3cm/y. From historical documents we can conceive that a great earthquake (M=8.4) occurred in 1854 as a result of a displacement of both the Suruga-Bay and Fujikawa faults. Recent crustal activity shows that strain accumulation is steadily going on around the two faults. In the near future, the crustal strain will provoke a left-lateral slip of these faults and result in a Tokai Earthquake.