Surface cracks appeared in a residential area, Minamiaso Village, at the time of the 2016 Kumamoto Earthquake

Numerous surface cracks appeared with displacements on the gentle slope in a residential area at the western foot of Takano-obane volcano in the western part of Aso caldera, central Kyushu, Japan, due to the 2016 Kumamoto Earthquake. The surface of the slope is composed of thick loam layer of approximately 10 m in thickness. The ground in the residential area has been arti-ficially modified for cultivated land, an ice-skating rink, and housing in the last three decades. Both horizontal and vertical displacements are recognized along most of the cracks. The former are several to thirty centimeters ; the latter are one meter or less. They are mainly E-W to ENE-WSW in strike, and a remarkable one extends more than 150 m long with northward sinking in the central portion of the area. Cracks with vertical displacements tend to appear in the northward zone of this major crack. The zone almost coincides with the outer periphery of the previous skate rink, so it is highly likely that sliding of embankment mate-rials along the cut slope of the rink occurred at the time of construction of the residential area. Therefore, such cracks might have been formed as settlement or displacement due to earthquake vibration.