Geological and geophysical studies of the Nojima Fault from drilling: An outline of the Nojima Fault Zone Probe

Authors
Citation
M. Ando, Geological and geophysical studies of the Nojima Fault from drilling: An outline of the Nojima Fault Zone Probe, ISL ARC, 10(3-4), 2001, pp. 206-214
Citations number
24
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Earth Sciences
Journal title
ISLAND ARC
ISSN journal
1038-4871 → ACNP
Volume
10
Issue
3-4
Year of publication
2001
Pages
206 - 214
Database
ISI
SICI code
1038-4871(200109/12)10:3-4<206:GAGSOT>2.0.ZU;2-B
Abstract
The Nojima Fault Zone Probe was designed to study the properties and recove ry processes of the Nojima Fault, which moved during the Hyogo-ken Nanbu ea rthquake (M(JMA)7.2) of 1995. Three holes, 500 m, 800 m and 1800 m deep, we re drilled into or near the fault zone by the Disaster Prevention Research Institute, Kyoto University. The 500 m and 800 m holes were drilled in Nove mber 1995, and in December 1996 the last hole reached its final depth of 17 60 m. The significant results are: (i) Geological and geophysical reconstru ction of the structure and evolution of the Nojima Fault was obtained; (ii) the maximum compression axis was found to be perpendicular to the fault, a pproximately 45 degrees to the regional compression stress axis; (iii) micr o-earthquakes (m = -2 to +1) were induced by water injections 1-3 km from t he injection points in the 1800 m hole; (iv) the fault zone was measured to be 30 m wide from microscopic studies of core samples. Instruments such as three-component seismometers, crustal deformation instruments, and thermom eters were installed in the holes.