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Title: |
Seismic Exploration at the TP-2 Geothermal Borehole in Takigami Geothermal Field in Japan Using the DFOS (Distributed Fiber Optic Sensing) System |
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Authors: |
Junzo KASAHARA, Yoko HASADA, Shigetsugu FURUYA, Masahiro HIMAZAKIi Hitoshi MIKADA, Hiroshi OHNUMA and Yasuhiro FUJISE |
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Key Words: |
DFOS, DAS, deep seismic reflectors, DTS, Vertical fault |
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Conference: |
Stanford Geothermal Workshop |
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Year: |
2025 |
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Session: |
Geophysics |
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Language: |
English |
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Paper Number: |
Kasahara |
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File Size: |
2938 KB |
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View File: |
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In 2022, we carried out a DFOS seismic study in the Takigami geothermal field in Kyushu, Japan. We installed an optical fiber cable to 2,000 m into depth the TP-2 geothermal borehole. We operated 12 seismic sources around the Takigami plant. The DTS temperature was 205ºC at 2,000 m depth. Based on the DAS data and calculated synthetic seismic waveforms, the E-W Vp depth profile shows a distinct vertical fault with an N-S strike concordant with the regional geology. Migrated reflection phases were obtained by F-K filtering for a better reflection image of the deeper part. The S-to-P converted phases were fortuitously observed by surface geophones when natural earthquakes occurred during the survey. We estimated the S to P conversions depths at around 1 km and 2.5 km depth.
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