Source-Rupture Process of the 2007 Noto Hanto, Japan, Earthquake Estimated by the Joint Inversion of Strong Motion and GPS Data

Abstract

The source-rupture process during the 2007 Noto Hanto earthquake, which was a reverse-faulting event located near the western coast of the Noto peninsula in central Japan, was estimated by the kinematic linear waveform inversion method. The waveform inversion was conducted by jointly using velocity waveforms recorded at 12 near-source strong-motion stations and static horizontal displacements recorded at 19 Global Positioning System (GPS) stations. In order to implement reliable Green’s functions into the inversion, a one-dimensional underground velocity structure for each individual strong-motion station was modeled through waveform modeling of an aftershock. The waveform inversion result showed the following image of the source-rupture process. The larger slip concentrated in the vicinity of the hypocenter, and it extended to the shallow portion of the source fault with a maximum slip of 5.1 m. The whole source process was characterized by the total seismic moment of 1.57×10[19] N · m (Mw 6.7) with the rupture duration of approximately 9 s. The obtained source model explained observed strong ground motions and GPS-measured static horizontal displacements well. The slip distribution correlated well with the spatiotemporal aftershock distribution, and the northeast end of the rupture was blocked by the resistive structure in the crust. From these facts, the 2007 Noto Hanto earthquake could be concluded as reactivation of preexisting seafloor active faults, F14 and F15, which were reported by the previous geophysical and geological surveys off the shore of the Noto peninsula.