Characteristics of the Lithology, Fault-Related Rocks and Fault Zone Structures in TCDP Hole-A

Song, Sheng-Rong; Kuo, Li Wei; Yeh, En Chao; Wang, Chien Ying; Hung, Jung Chou; Fong, Kuo

doi:10.3319/tao.2007.18.2.243(tcdp)

Cited by 53 publications

(42 citation statements)

References 24 publications

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“…The low resistivity is a result of infiltration of mud into highly fractured breccia based on core examination, and the low density, V p and V s , along with high V p /V s and Poisson's ratio in the gouge zone are attributable to large amounts of clay and/or fluid. Mineralogical analyses also show relatively high amounts of smectite and smectite/illite ration in FZ1111 compared to other fault zones (Kuo et al 2005;Song et al 2007). Because smectite, upon heating, easily transforms into illite or smectite/illite mixed layers (Ho et al 1999), the abundant smectite provides further evidence that FZ1111 was the slip zone during the Chi-Chi earthquake.…”

Section: Discussionmentioning

confidence: 96%

Subsurface Structure, Physical Properties, and Fault Zone Characteristics in the Scientific Drill Holes of Taiwan Chelungpu-Fault Drilling Project

Hung¹,

Wu²,

Yeh³

et al. 2007

Terr. Atmos. Ocean. Sci.

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: 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.

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Section: Discussionmentioning

confidence: 96%

Subsurface Structure, Physical Properties, and Fault Zone Characteristics in the Scientific Drill Holes of Taiwan Chelungpu-Fault Drilling Project

Hung¹,

Wu²,

Yeh³

et al. 2007

Terr. Atmos. Ocean. Sci.

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“…Multiple fault strands surrounded by damage zones, individually up to several meters thick, are documented to be localized within single lithologies (less than approximately 4 km depth) at the San Andreas Fault (Zoback et al 2010), Wenchuan Fault (Li et al 2013), Chelungpu Fault Depth, fracture total number distribution, fracture density (number of fractures per 1 m), neutron porosity, resistivity, density, P-wave velocity, natural gamma ray values, and Archie's cementation exponent m for the intact zones, surrounding damage zones, and the brecciated zones in the footwall are presented. (Song et al 2007), and the Nojima Fault (Tanaka et al 2007). These strike-slip and reverse faults occur within sedimentary lithologies and exhibit fault zone thicknesses ranging from several to approximately 135-m-thick damage zones.…”

Section: Implications Of the Relationship Between Fracture Density Anmentioning

confidence: 99%

Multiple damage zone structure of an exhumed seismogenic megasplay fault in a subduction zone - a study from the Nobeoka Thrust Drilling Project

et al. 2015

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To investigate the mechanical properties and deformation patterns of megathrusts in subduction zones, we studied damage zone structures of the Nobeoka Thrust, an exhumed megasplay fault in the Kyushu Shimanto Belt, using drill cores and geophysical logging data obtained during the Nobeoka Thrust Drilling Project. The hanging wall, composed of a turbiditic sequence of phyllitic shales and sandstones, and the footwall, consisting of a mélange of a shale matrix with sandstone and basaltic blocks, exhibit damage zones that include multiple sets of 'brecciated zones' intensively broken in the mudstone-rich intervals, sandwiched by 'surrounding damage zones' in the sandstone-rich intervals with cohesive faults and mineral veins. The fracture zones are thinner (2.7 to 5.5 m) in the sandstone-rich intervals and thicker in the shale-dominant intervals (2.3 to 18.6 m), which indicates a preference of coseismic slip and velocity-weakening in the former, and aseismic deformation in the latter. However, the surrounding damage zones observed in the current study are associated with an increase in resistivity, P-wave velocity, and density and a decrease in porosity, inferring densification and strain-hardening in the sandstone-rich intervals and strain-weakening in the mudstone-rich intervals. These observations indicate that the sandstone-rich damage zones may weaken in the short term but may strengthen in the geologically long term, contributing to a later stage of fault activity. In contrast, the mudstone-rich damage zones may strengthen in the short term but develop weak structures through longer time periods. The observed shear zone thickness in the hanging wall is thinner (2.3 to 18.6 m) compared to the footwall damage zones (12 to 39.9 m), possibly because faults in the hanging wall were concentrated and partitioned between the preexisting turbiditic sequence of alternating shale/ sandstone-dominant intervals, whereas in the footwall, faults were more sporadically distributed throughout the sandstone block-in-matrix cataclasites. A splay fault may evolve and be characterized by physical property contrasts, the lithology dependence of deformation, and the variability of damage zone thickness due to a heterogeneous lithology distribution in the hanging wall and footwall. The deformation patterns observed in the Nobeoka Thrust provide insights to the strain-hardening/weakening behaviors of sediments along megathrusts over geological timescales.

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“…As a consequence of this gap was that several international fault zone drilling projects have started to address fundamental questions about physical and chemical processes controlling faulting and earthquake generation (e.g. Hickman et al, 2004;Song et al, 2007;Zoback et al, 2007Zoback et al, , 2010Boullier, 2011). This paper is structured around a combined analysis of core samples from two drilling projects (San Andreas Fault Observatory at Depth/SAFOD; Taiwan Chelungpu-fault Drilling project/TCDP).…”

Section: Introductionmentioning

confidence: 99%

Faulting processes in active faults – Evidences from TCDP and SAFOD drill core samples

Janssen

Wirth

Wenk

et al. 2014

Journal of Structural Geology

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a b s t r a c tThe microstructures, mineralogy and chemistry of representative samples collected from the cores of the San Andreas Fault drill hole (SAFOD) and the Taiwan Chelungpu-Fault Drilling project (TCDP) have been studied using optical microscopy, TEM, SEM, XRD and XRF analyses. SAFOD samples provide a transect across undeformed host rock, the fault damage zone and currently active deforming zones of the San Andreas Fault. TCDP samples are retrieved from the principal slip zone (PSZ) and from the surrounding damage zone of the Chelungpu Fault. Substantial differences exist in the clay mineralogy of SAFOD and TCDP fault gouge samples. Amorphous material has been observed in SAFOD as well as TCDP samples. In line with previous publications, we propose that melt, observed in TCDP black gouge samples, was produced by seismic slip (melt origin) whereas amorphous material in SAFOD samples was formed by comminution of grains (crush origin) rather than by melting. Dauphiné twins in quartz grains of SAFOD and TCDP samples may indicate high seismic stress. The differences in the crystallographic preferred orientation of calcite between SAFOD and TCDP samples are significant. Microstructures resulting from dissolutioneprecipitation processes were observed in both faults but are more frequently found in SAFOD samples than in TCDP fault rocks. As already described for many other fault zones clay-gouge fabrics are quite weak in SAFOD and TCDP samples. Clay-clast aggregates (CCAs), proposed to indicate frictional heating and thermal pressurization, occur in material taken from the PSZ of the Chelungpu Fault, as well as within and outside of the SAFOD deforming zones, indicating that these microstructures were formed over a wide range of slip rates.

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Characteristics of the Lithology, Fault-Related Rocks and Fault Zone Structures in TCDP Hole-A

Abstract: ABSTRACT1 Department of Geosciences, National Taiwan University, Taipei, Taiwan, ROC

Cited by 53 publications

References 24 publications

Subsurface Structure, Physical Properties, and Fault Zone Characteristics in the Scientific Drill Holes of Taiwan Chelungpu-Fault Drilling Project

Subsurface Structure, Physical Properties, and Fault Zone Characteristics in the Scientific Drill Holes of Taiwan Chelungpu-Fault Drilling Project

Multiple damage zone structure of an exhumed seismogenic megasplay fault in a subduction zone - a study from the Nobeoka Thrust Drilling Project

Faulting processes in active faults – Evidences from TCDP and SAFOD drill core samples

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