HR: 0800h
AN: S21B-0568    [Abstracts]
TI: High magnetic susceptibility produced in high velocity frictional tests and heating tests on core samples from the Chelungpu fault in Taiwan
AU: * Tanikawa, W
EM: tanikawa@jamstec.go.jp
AF: Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology, 200 Monobe-otsu, Nankoku, Nankoku, 783-8502, Japan
AU: Mishima, T
EM: mishima@people.kobe-u.ac.jp
AF: Research Center for Inland Seas, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe, 657- 8501 Japan, Kobe, 657-8501, Japan
AU: Shimamoto, T
EM: shima007@hiroshima-u.ac.jp
AF: Department of Earth and Planetary Systems Science, Graduate School of Science, Hiroshima University, Higashi-Hiroshima, Higashi-Hiroshima, 739-8526, Japan
AU: Lin, W
EM: lin@jamstec.go.jp
AF: Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology, 200 Monobe-otsu, Nankoku, Nankoku, 783-8502, Japan
AU: Soh, W
EM: soh@jamstec.go.jp
AF: Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology, 200 Monobe-otsu, Nankoku, Nankoku, 783-8502, Japan
AB: We carried out high-velocity frictional tests and simple heating tests on crushed fault gouge from core samples from Hole B of the Taiwan Chelungpu-fault Drilling Project to investigate the cause of high magnetic susceptibilities in the fault core. Black ultracataclasite resembling that observed in Hole B formed during the experiments, even under low axial stress of 0.5 to 1.5 MPa. The bulk magnetic susceptibility of the tested samples was proportional to the frictional work applied and increased as slip increased. Thermomagnetic analysis of the samples before frictional testing revealed that magnetization increased at temperatures above 400°C, probably because of thermal decomposition of paramagnetic minerals. The decomposition of siderite and pyrite that changes to magnetite can explain high magnetic susceptibility and observed thermomagnetic curves. Simple heating also increased magnetic susceptibility though the change is much smaller compared to that by frictional tests. Both the thermally and mechanically induced formation of ferrimagnetic minerals by high velocity friction might have caused a magnetic susceptibility anomaly. Our experimental results support the assumption that heat generation of short duration, even if it is below the melting point, can increase magnetic susceptibility.
DE: 7209 Earthquake dynamics (1242)
DE: 8118 Dynamics and mechanics of faulting (8004)
DE: 8130 Heat generation and transport
DE: 8163 Rheology and friction of fault zones (8034)
SC: Seismology [S]
MN: 2007 Fall Meeting