Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Web of Science (5) Citing Articles via Google Scholar Google Scholar Articles by Han, R. Articles by Ree, J.-H. Search for Related Content GeoRef GeoRef Citation

Seismic slip record in carbonate-bearing fault zones: An insight from high-velocity friction experiments on siderite gouge

Raehee Han^*,1, Toshihiko Shimamoto^,2, Jun-ichi Ando³ and Jin-Han Ree⁴

¹ Department of Earth and Environmental Sciences, Korea University, Seoul 136-701, Republic of Korea
² Division of Earth and Planetary Sciences, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
³ Department of Earth and Planetary Systems Science, Hiroshima University, Higashi-Hiroshima 739-8526, Japan
⁴ Department of Earth and Environmental Sciences, Korea University, Seoul 136-701, Republic of Korea

Pseudotachylyte formed by frictional melting has been the only unequivocal evidence of past seismogenic fault slip. We report from high-velocity friction experiments on siderite-bearing gouge that mineral decomposition due to frictional heating also can leave evidence of paleoseismic events along shallow crustal faults other than pseudotachylyte. Experiments were conducted room dry on simulated gouge composed of siderite or mixture of siderite, calcite, and quartz, initially at room temperature, under normal stresses of 0.6–1.3 MPa and at seismic slip rates of 1.3–2.0 m/s. In all cases, gouge exhibited dramatic slip weakening and siderite was decomposed into nanocrystalline magnetite and CO₂ gas, as confirmed by CO₂ measurement, X-ray diffraction analyses, and transmission electron microscopy. The weakening was caused by the low frictional strength of ultrafine decomposition products at seismic slip rates. Magnetite formation during shearing changed gouge color to black and increased magnetic susceptibility by a few orders of magnitude. Those changes can be recognized in natural fault zones, and black gouge in the Chelungpu fault zone in Taiwan is perhaps such an example. Thus our results suggest that thermal decomposition in shallow crustal faults can be an important co-seismic process not only for dynamic fault weakening, but also for leaving seismic slip records.

Key Words: seismic fault slip • thermal decomposition • black gouge • siderite • magnetite • dynamic fault weakening