Scientific Result of material analyses of the Taiwan Chelungpu fault Drilling Project (TCDP)

概要

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The Chelungpu fault that had displaced in the Chi-Chi, Taiwan, earthquake in 1999, shows difference in behavior of earthquake slip between the northern and middle-to-southern fault segments in the earthquake fault. The reason why such difference was taken place is likely to cause reduction of the coseismic frictional strength in the earthquake fault. To examine it from the ground truth, the Taiwan Chelungpu fault Drilling Project (TCDP) was conducted, then target for the borehole logging and core sample analyses had been successfully achieved as the International Continental Drilling Program (ICDP). This paper overviewed the TCDP scientific results particularly on the mechanism to cause the coseismic reduction of friction strength of the earthquake fault from the view points of 1) temperature increase, caused by the shear heating, to be estimated by the flux of rare earth element and 2) expansion of the fault material deduced from the porosity change. Here two models; the elastohydrodynamic lubrication and the thermal pressurization to be proposed (Ma et al., 2003), were examined, consequently the author assumed that the fault materials behaved as non-Newtonian particle-powder-water mixture during the earthquake then that the latter model is much appropriate in observation result and rheologic characteristics for this case is proposed.
独立行政法人海洋研究開発機構の論文