Coseismic displacement field and slip model derived from near-source strong motion records of M_W7.0 Kumamoto, Japan, earthquake

Near-source coseismic displacement field of the 16 April 2016 M_W7.0 Kumamoto, Japan, earthquake is estimated from 94 digital strong motion records after correction for their baseline errors using an improved empirical method SMBLOG, and compared with that from 57 GPS observations published by Geospatial Information Authority of Japan (GSI). Furthermore, three slip models of the earthquake are inverted from the displacement data of the GPS, strong motion and their combination, suggesting the results are in good agreement. The three models all show that the earthquake is dominated by the right-lateral strike-slip mechanism (also a few normal-fault dislocations). The maximum horizontal and vertical coseismic displacements reached 104.5 cm and 58.0 cm, and occurred at the stations KMMH162 and KMM005, respectively. The fault slips are mainly distributed around the second event (about 20 km northeastward from epicenter) and in an area of about 40 km along the strike and 20 km along the dip. The moment magnitude is estimated to be M_W7.1, and the peak slip is about 5.10 m for strong motion data and 5.87 m for GPS. The surface rupture should be obvious. Moreover, the comparison of the three-component coseismic displacements derived from 12 GPS-strong motion station-pairs with interval less than 3 km also indicates that the lower limit is about 2 cm for earthquakes of magnitude about 7 when SMBLOC method is used.