DEEP SUBSURFACE S-WAVE VELOCITY STRUCTURE IN THE AMAMI ISLANDS, TOKARA ISLANDS, AND YAKUSHIMA ISLAND, JAPAN

In this study, the deep subsurface S-wave velocity (Vs) structure was estimated using microtremor array data on the Amami and Tokara Islands, and Yakushima Island in Japan. The depth of the top of the seismic basement was about 2.0 km, with the largest depth located at Kikaishima Island in the Amami Island Group; the depths at the other islands ranged from 0.2 to 0.6 km. The mean Vs values for each layer and the layer boundary depths at each location under a four-layer model were 0.69, 1.02, 2.18, and 3.49 km/s. These mean values were close to those of the Yaeyama, Miyako, and Okinawa Islands. These results can be used to improve the structural Vs model of the Nansei Islands.