Temporal change in permeability of the Nojima fault zone by repeated water injection experiments

Extreme hydrothermal conditions at an active plate-bounding fault

“…1). Borehole injection experiments, earthquake aftershock studies, and laboratory experiments on fault zone materials reveal that the earthquake process perturbs the fault zone, which then heals during the post-seismic period [22][23][24][25][26] .…”

Changes in permeability of the Nojima fault damage zone inferred from repeated water injection experiments

“…Water pressure in the 800-m borehole was not successfully measured in 2009 because of a problem with the measurement system. Therefore, for this study we recomputed the results of the experiments conducted from 1997 until 2003, which differ from the permeabilities reported in Kitagawa et al (2007), and added the results obtained during the 2004 and 2006 experiments; then, using the combined results, we investigated temporal changes in permeability of the fractured zone near the Nojima branch fault.…”

“…The water head in the 800-m borehole is higher than the surface; thus, the borehole is an artesian well. Until August 2000, the top of the borehole was open, so the discharge rate from the borehole was measured (Kitagawa et al 2007). In August 2000, the borehole was sealed, so after that the water pressure was measured in the borehole with a pressure gauge.…”

“…The objective of the Nojima fault zone probe project is to study the properties and recovery processes of the fault zone (Ando 2001). Kitagawa et al (2007) showed by groundwater observations that from 1997 to 2003 the permeability of the fractured zone near the fault decreased, and observations of crustal strain (Mukai and Fujimori 2007) and self-potential (Murakami et al 2007) during the same period supported their findings.…”

宮城県沖大地震の前兆を捉えるための深層地下水変動研究：2004年6月～2007年12月の観測結果

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