Strong-motion modeling of the 1980 Izu-Hanto-Toho-Oki earthquake by inversion method ( Japan).

Near-field strong-motion records (DELTA <60km) are modeled to estimate the spatial distribution of seismic moment for the 1980 Izu-Hanto-Toho-Oki earthquake (M_JMA 6.7). An inversion method involving a Mellman's error function is used to interpret the strong-motion waveforms in the period range of 3 to 20 sec. The earthquake source is approximated by point dislocations distributed uniformly and densely over the fault plane. The fault plane is discretized into subfaults each having constant seismic moment. The seismic moments of the subfaults are taken as free parameters in the inversion. By comparison of our solutions with the seismicity before and after the mainshock, it is found that the rupture front could not go across the swarm area near the hypocenter during the mainshock. -from Author