Mesoscopic Structural Observations of Cores from the Chelungpu Fault System, Taiwan Chelungpu-Fault Drilling Project Hole-A, Taiwan

Sone, H.; Yeh, En Chao; Nakaya, T.; Hung, Jung Chou; Fong, Kuo; Wang, Chien Ying; Song, Sheng-Rong; Shimamoto, Toshihiko

doi:10.3319/tao.2007.18.2.359(tcdp)

Cited by 29 publications

(31 citation statements)

References 12 publications

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“…Moore and Rymer, 2012;Holdsworth et al, 2011;Bradbury et al, 2011;Mittempergher et al, 2011;TCDP: Ye et al, 2007;Sone et al, 2007;Ishikawa et al, 2008;Boullier et al, 2009). Here we describe selected SAFOD and TCDP samples to illustrate similarities and differences in fault rock composition.…”

Section: Fault Rock Compositionmentioning

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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Section: Fault Rock Compositionmentioning

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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“…FZ1241 is a normal fault; the remaining three thrust faults can be categorized as part of the Chelungpu fault system. A detailed architecture of above fault zones was discussed in Sone et al (2007). The 6 zones below this point are within the Kueichulin Formation and can be grouped as the Sanyi fault system.…”

Section: Subsurface Structure and Fault Zone Characteristicsmentioning

confidence: 99%

“…Both microscopic observations of thin-sections and XRD analyses show that major mineral compositions are similar in both fault and host rocks (Isaacs et al 2007). FZ 1111 is beddingparallel consisting of fault breccia and fault gouge 1109 to 1112 m. The degree of fracturing increases from the top of the damage zone towards the gouge zone in which the fabrics changed from massive to foliate between 1110.25 and 1111.35 m. The Chi-Chi major slip zone (MSZ, about 2 cm thick) is contained within the 12-cm thick primary slip zone (PSZ), which is located near the bottom of this broad gouge zone Sone et al 2007). FZ1710 is a major Sanyi fault zone that also contains about 1-m clayey gouge and a thrust fault type with nearly consistent bedding attitude in both the hanging-and footwalls (see Fig.…”

Section: Subsurface Structure and Fault Zone Characteristicsmentioning

confidence: 99%

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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“…At the TCDP drillsite, a fault zone at ~1111 m depth is interpreted as the 1999 slip surface (for example, Hung and Ma 2006;Hung et al 2007;Sone et al 2005Sone et al , 2007). This fault zone contains <1 m of light gray, wet, massive clay that grades into ~10 -15 cm of foliated fault gouge.…”

Section: Taiwan Chelungpu-fault Drilling Project (Tcdp): Taichungmentioning

confidence: 99%

Structural, Mineralogical, and Geochemical Characterization of the Chelungpu Thrust Fault, Taiwan

Isaacs¹,

Evans²,

Song³

et al. 2007

Terr. Atmos. Ocean. Sci.

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The Chelungpu fault, Taiwan, produced a northward propagating rupture on 21 September 1999 resulting in a M w 7.6 earthquake with a ~90 km long N-S trending fault scarp. The mineralogic and physical character of the fault-related rocks within the Chelungpu fault zone, as measured at 9 sites along 70 km of the 1999 rupture trace, changes significantly along strike and with depth. The northern section of the Chelungpu fault has a 10 -30 m-wide primary damage zone that is characterized by increased fracture density and alteration, but little microstructural damage to within 1 m from the main fault. The southern section of the Chelungpu fault has a 25 -70 m wide primary damage zone that is characterized by increased fracture density and alteration, the presence of intensely sheared rock, and numerous secondary faults and gouge zones as far as 240 m from the main fault. The complexity of the damage zone, geochemistry, and clay mineralogy of the southern fault zone may reflect its relative maturity (~1 Ma) compared to the northern fault zone (~46 -100 Ka). The major down-dip mineralogic variation is a transition from a significant amount of smectite in exhumed fault cores to little or no smectite in the fault core at sampled depths of 200 to 1000 m. This transition may be influenced by weathering processes at the surface, however co-seismic fluid flow may have a role in illite-smectite reactions. The composition of clays has important seismologic implications as clays play a role in fault weakening.

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Mesoscopic Structural Observations of Cores from the Chelungpu Fault System, Taiwan Chelungpu-Fault Drilling Project Hole-A, Taiwan

Cited by 29 publications

References 12 publications

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

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

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

Structural, Mineralogical, and Geochemical Characterization of the Chelungpu Thrust Fault, Taiwan

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