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| | Abstract | | The 2016 Kumamoto earthquake caused heavy damage to Aso area. One of the disasters is the dormant of some hot springs in Uchinomaki area in the northwest of the Aso caldera. Some surveys were conducted after the earthquake. For example, satellite data and borehole data demonstrated that. Horizontal slide occurred along the geological formation at ~50 m depth. However, geological formation and structures in the hot spring area have not been revealed. In this study, we performed microtremors array measurements at 48 sites in Uchinomaki area from 11th to 17th of June, 2017. We applied Spatial Auto Correlation (SPAC) method for observed microtremor data to estimate surface-wave dispersion curves. S-wave velocity profiles were then obtained by inversion of the observed dispersion curves. In the spatial distribution of the inverted S-wave velocities, we can see horizontally layered structure beneath the hot spring area and another structure with fast S-wave velocity at the central part of hot spring area and along the somma. |
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