To establish reliable methods for determining the thermal conductivity of drilled core and cuttings samples, we measured thermal conductivity for a series of sliced specimens of sandstone from India and compressed kaolin powder. The results showed that specimen size required for precise measurement is more than 100 mm in length, 40 mm in width, and 20 mm in thickness for most rocks and sediments collected from drilling in which a box-type probe is used. In addition, a positive correlation was recognized between the bulk density of compressed kaolin powder and its thermal conductivity value. We believe that it is possible to determine thermal conductivity of disaggregated geomaterials and cuttings recovered during drilling by using a needle-type probe and a small sample holder in which the cutting sample is placed and pressed to remove pore space.

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To evaluate the porosity profile within the Chelungpu Fault, which slipped during the 1999 Taiwan Chi-Chi Earthquake, we performed X-ray computed tomography imaging of core samples from Hole B of the Taiwan Chelungpu Fault Drilling Project. We established the relationship between the degree of X-ray attenuation and wet bulk density and obtained a porosity profile through the major fault zone at 1,136 m depth. The shear zones within the fault zone generally showed high porosity, and the porosity of the shear in the black gouge zone, which previous research suggests was the slip plane for the 1999 earthquake, was deduced to be 33.0%. This high porosity might indicate dilative shear deformation during the earthquake.

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Extremobiosphere Research Center (XBR) have been challenging to discover not only basic studies for Marine Microbiology, Biology and Ecosystems, but also their application studies for contributing to develop our society and economy. Then we have obtained many creative scientific results, and useful biomaterials cooperation with the industrial companies. In this article, the research topics of three programs, Extremophiles Research Program, Cooperative Research Project for Extremophiles and Deep Subsurface Extremophiles Research Program, were introduced and their summaries were described. The detailed report of those three programs results was published separately with this report, in the book “Research Report of Extremobiosphere Research Center (March, 2009, JAMSTEC)”. By the way, the report of another program of XBR, Marine Biology and Ecology Research Program, was published in JAMSTEC-R Vol. 9, number 1.

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The Institute for Research on Earth Evolution (IFREE) consists of five programs. During this five-year period, each program has pursued its own research targets, but at the same time each has made a considerable effort to work with other programs on subjects otherwise not easily approached. By selecting eight such subjects, we review our work in the 2004-2008 period.

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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.

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