Gravity Changes on Izu Peninsula

Abstract

The 1974 Izu Hanto-oki earthquake occurred with a right-lateral strike-slip motion of Irozaki fault inducing vertical and horizontal displacements of the peninsular crust. As compared the postseismic gravimetric results with the 1970 ones, gravity increase up to 4060 μgals was detected on the southeastern coast of Izu Peninsula by assuming no gravity change at BM 9402 on the northwestern coast. Possible causes of the gravity changes are presumed on the basis of geodetic results including the faulting motion. It is concluded that the gravimetric results reflect the earthquake-induced density increase plus the gradual peninsula-wide crustal deformation independent of the earthquake induction.