ESTIMATION OF SUBSURFACE STRUCTURES AND GROUND MOTION CHARACTERISTICS IN THE AREAS DAMAGED IN THE 2016 CENTRAL TOTTORI PREFECTURE EARTHQUAKE IN JAPAN

Abstract

On 21 October 2016, an earthquake with a magnitude of 6.6 (determined using the Japan Meteorological Agency’s [JMA] seismic network) occurred in the center of Japan’s Tottori Prefecture. In the city of Kurayoshi and in the towns of Yurihama and Hokuei, JMA seismic intensities of lower 6.0 were observed, and structural damage to housing was concentrated in a limited number of areas. This research conducted microtremor observations around damaged areas and used previous studies to estimate subsurface structures and ground motion characteristics. Low-velocity layers with an S-wave velocity of between 80 and 200 m/s were estimated at all observation sites and a tendency is present for the thickness to increase towards the coastal plains and decrease inland. In an evaluation of the relationship between ground motion characteristics and earthquake damage, researchers found that the occurrence of damage correlated to significant changes in layer thickness. Researchers believed that the damage correlates to the 2-D or 3-D effects of subsurface structures