JpGU-AGU Joint Meeting 2017

Presentation information

[JJ] Oral

S (Solid Earth Sciences) » S-SS Seismology

[S-SS17] [JJ] Fault Rheology and Earthquake Physics

Sat. May 20, 2017 10:45 AM - 12:15 PM A09 (Tokyo Bay Makuhari Hall)

convener:Takanori Matsuzawa(National Research Institute for Earth Science and Disaster Resilience), Takeshi Iinuma(National Research and Development Agency Japan Agency for Marine-Earth Science and Technology), Wataru Tanikawa(Japan Agency for Marine-Earth Science and Technology, Kochi Instutute for Core Sample Research), Hideki Mukoyoshi(Department of Geoscience Interdisciplinary Graduate School of Science and Engineering, Shimane University), Chairperson:Hideki Mukoyoshi(Department of Geoscience Interdisciplinary Graduate School of Science and Engineering, Shimane University), Chairperson:Jun Kameda(Earth and Planetary System Science Department of Natural History Sciences, Graduate School of Science, Hokkaido University)

12:00 PM - 12:15 PM

[SSS17-06] Detection of increased heating and estimation of coseismic shear stress from Raman spectra of carbonaceous material in pseudotachylytes

*Keisuke Ito1, Kohtaro Ujiie2, Hiroyuki Kagi3 (1.University of Tsukuba, 2.Graduate School of Life and Environmental Sciences, University of Tsukuba, 3.Geochemical Research Center, Graduate School of Science, The University of Tokyo)

Keywords:carbonaceous material, Raman spectra, pseudotachylyte, frictional heating, coseismic shear stress

Frictional heat generated during earthquakes provides insight into the coseismic fault strength. To detect increased heating associated with faulting at seismic slip rates, we analyzed the Raman spectra of carbonaceous material in natural and experimental pseudotachylytes derived from argillite. The results indicate that the increased carbonization in pseudotachylytes relative to the host rocks could be detected when the ambient temperature is lower than 280 °C. This increased carbonization can occur in ~4–16 s and is preserved even after alteration of pseudotachylytes. The comparison between experiment and Raman data demonstrated that there is a correlation between the average shear stress and the Raman spectra in pseudotachylytes. The average coseismic shear stress estimated from the correlation was 1.8 MPa. The resulting apparent friction coefficient under hydrostatic conditions at depths of 4–6 km was ~0.03–0.05. Raman analysis of carbonaceous material-bearing pseudotachylytes will be useful for estimation of coseismic fault strength.

Ito, K., K. Ujiie, and H. Kagi (2017), Detection of increased heating and estimation of coseismic shear stress from Raman spectra of carbonaceous material in pseudotachylytes, Geophys. Res. Lett., in press.