: 1) a bedding-parallel thrust fault with a 30-degree dip; 2) the lowest resistivity; 3) low density, V p and V s ; 4) high V p /V s ratio and Poisson's ratio; 5) low energy and velocity anisotropy, and low permeability or fluid mobility within the homogeneous gouge zone; 6) increasing gas (CO 2 and CH 4 ) emissions; and 7) being rich in smectite within the primary slip zone.Formation physical properties hold consistent relationships with either depth or lithology. Anisotropy of shear-wave velocity shows that the dominant fast shear polarization direction is in good agreement with an overall azimuth of the maximum horizontal stress axis, particularly within the strong anisotropic Kueichulin Formation. A drastic change in orientation of fast shear polarization across the Sanyi thrust fault at a depth of 1710 m reflects changes in stratigraphy, physical properties and structural geometry.

Stratigraphy, sedimentary fades, and deformation characteristics of drill cores from Fengyuan and Noutou wells reveal important attributes for the westmost portion of active Chelungpu thrust fault and contrasting deformation mechanisms between the north and south ends. Stratigraphy of the Fengyuan well (including BH-1 and BH-lA boreholes) is composed of three major units, including the upper Miocene to Pliocene Kueichulin Formation (455.4-224.7 m), the Pliocene Chinshui Shale (224.7-3.9 m) and recent terrace deposits (3.9-0 m). The Kueichulin Formation comprises three upward coarsening, tide-dominated delta parasequences with sandstone and sandstone-Shale alternations. The Chinshui Shale is dominated by shallow marine fades with siltstone, mud stone and fine-grained sandstone. Shallow marine fades are occasionally intercalated with tide-dominated delta deposits. Terrace deposits are char acterized by paleosol, yellowish mud, mottled leaching soil and thin pebble layers. The Chi-Chi earthquake slip zone is lo cated at a transgressive deposit, which is also the sequence boundary between the Kueichulin Formation and the Chinshui Shale. Other two major brecciated shear zones are also the parasequence boundaries within the Kueichulin Formation. Stratigraphic sequence of the Nanton well (CLF-2) is composed of the Pleistocene Toukoshan Formation (211.9-177 m) in the footwall, and the Chinshui Shale (177-8.7 m) and terrace deposits (8.7-0 m) in the hanging wall. The Toukoshan Formation is characterized by alternation of conglom erates and yellowish fine-grained deposits with drifted pebbles, an indica tion of braided fluvial deposits. The Chinshui Shale comprises alternating shallow marine and tidal deposits. The shallow marine face is dominated

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