Complicated repeating earthquakes on the convergent plate boundary: Rupture

Source rupture processes of the 1978 and 2005 Miyagi-ken Oki earthquakes are revealed using waveform inversion. Though the hypocenters are almost the same and both rupture from the hypocenter to the deep part, our results show that these two earthquakes did not repeat the same rupture. In the case of the 2005 earthquake, several small asperities are all confined in the southern part, where it probably ruptured with a similar value of slip in 1978. The coupling factor of the subducting slab with the continental plate in the southern part is about 0.5. Main rupture of the 1978 earthquake, however, occurred in the northern part, where no slip is identified for the latest one. The seismic moment of the 1978 earthquake is four times of that of the 2005 earthquake. The Miyagi-ken Oki earthquake repeats in a very complex pattern. It may rupture only on those small asperities like the 2005 earthquake, or propagate to the northern large asperities like the 1978 one, or even develop to a vast earthquake rupturing to the shallow part and generate a large tsunami like the 1793 one