Crustal Deformation Caused by the 2016 Kumamoto Earthquake Revealed by GEONET

Abstract

GNSS observation over the area of the 2016 Kumamoto Earthquake (April 14-16, 2016) reveals coseismic deformations of over 10 centimeters caused by the two large foreshocks and of approximately 1 meter caused by the mainshock as well as a postseismic deformation of up to a few centimeters. Large displacements are concentrated around Futagawa-Hinagu fault zone which is a known active fault in Kyushu Island. Kinematic positioning results imply the two large foreshocks initiated a rupture on the northern part of the Hinagu fault segment, then a rupture neighboring the southern part of the segment. The postseismic deformations that followed seem to be similar to the pattern of coseismic deformation, however, they are widely distributed. The sequence of earthquakes caused significant distortion in the Japanese geodetic datum around the focal area, but GEONET observation enabled a rapid response. Furthermore, it is believed the observation data provided by GEONET will make a significant contribution to understand the fault property along the active fault zone.