2006年大分県中部の地震の震源特性

概要

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A moderate size intraslab earthquake occurred on 12 June, 2006 at the depth of about 145 km in the Philippine Sea Plate beneath central Oita. Focal mechanism solution determined by F-net shows that this event has a down-dip extension focal mechanism and aftershock activity of this event is very low. Observed displacement waveforms indicate rupture propagates on the east-dipping nodal plane. To investigate source process of this event, inversion of strong motion waveforms is carried out. Result shows complex rupture propagation during this earthquake. Largest slip area is located near the hypocenter. Snapshots show rupture propagates to the right upper direction on the fault plane at first and change to the left upper direction after few seconds. Based on inversion result, the characterized source models of 2006 event are constructed. In this study source models with one and two asperities are proposed. Simulations using the empirical Green's function method suggest that the source model with two asperities is preferable but detail rupture process of this event is much more complex.
2010-03-19