THE RELATIONSHIP BETWEEN HOUSING DAMAGES AND GROUND MOTION CHARACTERISTICS DUE TO THE 2016 CENTRAL TOTTORI PREFECTURE EARTHQUAKE, JAPAN

Abstract

 On October 21, 2016, an earthquake with M_JMA 6.6 occurred in the central part of Tottori Prefecture, Japan. Observed JMA seismic intensities were 6 lower at Kurayoshi city, Yurihama and Hokuei towns. Housing damages due to the earthquake were concentrated in limited areas. In this study, we carried out microtremor observations around damaged areas, and estimated velocity structures and ground motion characteristics including previously conducted studies. We confirmed relationship between ground motion characteristics and damages due to the earthquake. Low-velocity layers with S-wave velocity less than 200 m/s were estimated at all observation sites and the layers tend to be thicker to coastal plain and thinner to inland areas. Thicknesses to deeper layers with S-wave velocity more than 700 m/s were different in west and east of Hokuei town from earthquake ground motion data. However, estimated ground responses with one-dimensional velocity structures do not match well with the observed damages in the target area. The damages mainly occurred in the area where sedimentary layer thickness changes drastically, and it is suggested that two-dimensional or three-dimensional irregularity of subsurface structure affects much on the damages.