| 講演要旨(和文) | | 超臨界貯留層の地震学的イメジング手法のフィージビリティ研究の一環として，2018年に九州指宿地熱地帯にあるメディポリス地熱発電所にて試験観測を実施した．観測井内に光ファイバーを設置し，深度1000 mまでのDAS（分布型振動センサ）による地震波観測とDTS（分布型温度センサ）による温度測定を行った．最高温度は深度914 mで264度であった．DASと地表に設置した地震計で，4日半の連続観測を行い，周辺地域で発生した7つの自然地震を観測した．南方100 kmで起きたM5.2の地震は震源の深さ123 kmで，観測井の977 mから地表までのすべてで観測された．高温領域での地震波の減衰はほとんど見られず，P波速度は約4 km/sであった．すべての地震のセンブランス解析により，観測井におけるP波速度構造を推定した． |
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| | 講演要旨(英文) | | We conducted a feasibility study in 2018 in a geothermal field, Kyushu, Japan. We installed a fiber-optic cable down to 977 m in the borehole and measured the temperature and acquired seismic data in the borehole by distributed temperature sensor (DTS) and distributed acoustic sensor (DAS) modes, respectively. The measured highest temperature was 264 degC at the 914 m depth. We obtained 4.5 days of the continuous seismic monitoring via DAS and surface seismometers. The seismic system observed seven natural earthquakes occurring in surrounding region. One of the earthquakes with M5.2 at 100 km south of the DAS system occurred at 123 km depth and were observed by a whole depth of 977 m to 0 m. It is identified that less or no attenuation of seismic amplitudes at high temperature zone and Vp is approximately 4 km/s at this zone. By semblance analysis of all earthquakes, we obtained Vp profile in the borehole. |
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