Damage Islands in Mashiki Town from the 2016 Kumamoto Earthquakes

We investigated the distribution of the collapsed buildings due to the 2016 Kumamoto earthquakes in the area along the Akitsu river. A Mj6.5 foreshock and Mj7.3 mainshock occurred within 28 hours. The spatial pattern of collapsed buildings from the foreshock and mainshock were similar and the isolated areas resemble islands. Since the surface rupture occurred only during the mainshock, it is unlikely that the presence of the surface rupture generated the similar damage patterns for the foreshock and mainshock in Mashiki. The most severely damaged areas are located in the lowest river terrace. The isolated islands correspond to the locations of built areas constructed during the Meiji era. The cause of the damage islands is likely to be a combination of the subsurface soil structure and age of buildings.