Earth Planets Space, Vol. 59 (No. 11), pp. 1155-1171, 2007
Wataru Suzuki and Tomotaka Iwata
Disaster Prevention Research Institute, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan
(Received April 1, 2007; Revised September 30, 2007; Accepted October 23, 2007; Online published November 30, 2007)
We estimate the source model of the 2005 Miyagi-Oki earthquake, which consists of two source patches called "strong motion generation areas (SMGAs)", to explain the broadband strong motions. The location of the first SMGA is determined from the arrival time differences between the first motion and the first pulse in the P-wave portion. Based on the broadband waveform modeling obtained using the empirical Green's function method, we estimate the parameters of the two SMGAs. The estimated location of the two SMGAs coincides with the two major large slip areas inferred from the inversion of strong-motion and teleseismic waveforms, which implies that the broadband strong motion of the 2005 Miyagi-Oki earthquake mainly radiates from the asperities. The deeper SMGA has a larger stress drop (34.1 MPa) than the shallower one (17.6 MPa). Comparison of the locations of SMGAs between the 2005 and 1978 Miyagi-Oki earthquakes suggests that they do not overlap with each other. The interplate earthquakes, including this event, were found to have smaller SMGAs than those predicted from the relationship of crustal earthquakes for a given seismic moment. This implies that the stress drop of the SMGAs for interplate earthquakes is larger than that for crustal earthquakes.
Key words: 2005 Miyagi-Oki earthquake, empirical Green's function method, broadband strong motion, source model, interplate earthquake.