Source Process of the October 2016 Tottori-Chubu Earthquake(<i>M</i>j 6.6) and Relation with Near Source Strong Motions

Abstract

A source process inversion for an Mj 6.6 earthquake which occurred on October 21, 2016 in central Tottori Prefecture, was performed using near-field strong motion waveforms. The results showed that a left-lateral strike-slip component was dominant on the fault plane, the strike of which was in a NNW-SSE direction and the dip almost vertical. The moment magnitude was estimated as 6.2. A large slip area (asperity) was determined around the hypocenter, including its northern shallow part, in which the maximum slip was nearly 1.2 m. Another small asperity was estimated also near the northern edge of the fault plane. These two asperities corresponded to the two distinct wave packets observed at the stations near the source region. Furthermore, the results suggested that a discrepancy in frequency characteristics between these asperities existed, by comparing them with waveforms obtained just above the source region. We also estimated the stress drop on the fault plane by the final slip distribution, and the maximum value was about 16 MPa. This result meant that the strong ground motion excitation of this earthquake was of an average level compared to past crustal earthquakes in Japan.