An intermediate deep earthquake rupturing on a dip‐bending fault: Waveform analysis of the 2003 Miyagi‐ken Oki earthquake

[1] Using waveform analysis, we propose a dip-bending fault model for the 2003 Miyagi-ken Oki earthquake. Dip angle of the upper fault plane is estimated as 87° on the basis of focal mechanism from P-wave first motions. S-wave polarization analysis leads to a dip angle of 60° for the lower portion of the fault plane. Inversion results show that the rupture started on the southern fault plane. In the beginning 5 seconds, slip was mainly confined in the hypocenter area on the southern fault. From 5 seconds on rupture propagated to the northern part, where the largest slip (3 m) occurred in the northern deep part. The complex stress field in the slab and compositional difference in the upper and the other portion of the slab account for such a bending fault even at intermediate depth.