5:15 PM - 6:30 PM
[MIS34-P29] Co- and post-seismic displacements due to the 2016 Kumamoto earthquake observed by GEONET
Keywords:The 2016 Kumamoto earthquake, GEONET, crustal deformation, Kinematic GNSS analysis
The GEONET data are processed with three kinds of routine analyses: F3 (24-hour session), R3 (24-hour session), and Q3 (6-hour session). Since two foreshocks on April 14 occurred consecutively within three hours, the coseismic displacements could not be detected from the routine analyses separately. Therefore, an emergency analysis (S3) for static solutions with arbitrary session length, and GEONET real-time analysis (REGARD), which offers 1 Hz kinematic solutions, were also used to detect the coseismic deformations.
Clear coseismic displacements due to the Kumamoto earthquake were observed: NE displacement of 20 cm and subsidence of 3 cm was found at site 1071 near the Hinagu fault during the two foreshocks. NE displacement of 75 cm and subsidence of 20 cm, and SW displacement of 97 cm and uplift of 28 cm were detected just after the mainshock at sites 0465 and 0701, which are located near the Futagawa fault, respectively (Figure). Postseismic deformation up to 3 cm also has been observed, showing a roughly similar deformation pattern to those associated with the mainshock.
The results implicate that the two foreshocks occurred at the Hinagu fault, and the mainshock occurred at Futagawa fault. Especially, the observed displacements indicate that the mainshock ruptured from the epicenter to east with a lower dip angle compared to the foresocks. We plan to investigate the fault slips for the sequence of the earthquakes and continue to monitor the postseismic deformation.