2000年野島断層注水試験に伴う微少地震活動の観測

概要

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After the 1995 Hyogo-ken Nanbu earthquake, a scientific drilling program called the Nojima Fault Zone Probe was carried out on the Nojima fault which ruptured during the 1995 earthquake. In 1997, a water injection experiment was carried as part of the program. A second water injection experiment was conducted from January to March 2000 (1/11: failed, 1/22-26: 3MPa, 1/31-2/5: 4MPa, 3/3-3/11: 4.5 MPa). We monitored changes of earthquake activity before and after the water injections. We deployed a temporary seismic network around the water injection site consisting of four telemetered seismic stations, six borehole seismometers, and five off-line seismographs. The 800-m-deep borehole seismometer detected 711 events with an S-P time of less than 1.0 s from December 1, 1999 to May 18, 2000. Clustered seismicity occurred several times during the period. Among the detected microearthquakes, 329 events were located with locational errors of less than 1 km. Most of these are distributed in three regions at depths of less than 5 km.
東京大学の論文