Analyses of pseudotachylyte from Hole-B of Taiwan Chelungpu Fault Drilling Project (TCDP); their implications for seismic slip behaviors during the 1999 Chi-Chi earthquake

Otsuki, Kenshiro; Hirono, Tetsuro; Omori, Masahiro; Sakaguchi, Masumi; Tanigawa, Wataru; Lin, Weiren; Soh, Wonn; Rong, Sheng-Song

doi:10.1016/j.tecto.2009.01.008

Cited by 22 publications

(20 citation statements)

References 64 publications

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“…They observed no indication for higher temperatures (N250°C-260°C) and suggest that the observed high illite content (N70%) instead may be attributed to combined comminution and dissolution-recrystallization processes during multiple past slips. In our samples, we did not find any amorphous material/melt in TEM images as described for example in SAFOD and TCDP material (Janssen et al, 2010;Otsuki et al, 2009) or any silica gel on fault surfaces . Thus, we consider it unlikely that the observed enrichment of smectite results from transformed frictional melt.…”

Section: Gouge Composition and Shear Strengthsupporting

confidence: 46%

Co-seismic and/or a-seismic microstructures of JFAST 343 core samples from the Japan Trench

et al. 2015

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Section: Gouge Composition and Shear Strengthsupporting

confidence: 46%

Co-seismic and/or a-seismic microstructures of JFAST 343 core samples from the Japan Trench

et al. 2015

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“…Pseudotachylites with typical melt structures (e.g. vesicles, spherulites) have also been described in samples from Hole B of TCDP (Hirono et al, 2006;Otsuki et al, 2009). For Hole A, Kuo et al (2009Kuo et al ( , 2011 described pseudotachylites with vesicles of about 1e40 mm diameter within the PSZ (1111-m Zone).…”

Section: Amorphous Material/meltingmentioning

confidence: 90%

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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“…This critical value can be higher if we consider a higher pore pressure caused by thermal or thermochemical pressurization, but, at the same time should be lower than 343°C which would correspond to a pore pressure equal to the lithostatic pressure (<15 MPa). In fact, as constrained from various temperature proxies (fission tracks, reaction kinetics, magnetic analysis, and trace elemental and isotopic analyses, as well as Raman spectra, vitrinite reflectance, and biomarkers of carbonaceous materials) [e.g., Mishima et al ., ; Hirono et al ., , ; Sakaguchi et al ., ; Ishikawa et al ., ; Hamada et al ., ; Otsuki et al ., ; Kuo et al ., ; Savage et al ., ; Yang et al ., ], much higher temperatures (>276°C) have been reported for the slip zones associated with the aforementioned earthquakes. Taking the 1999 Chi‐Chi earthquake, for example, where the principal fault slip occurred at ~300 m depth in the Chelungpu scientific drilling [ Tanaka et al ., ], magnetic analysis of the slip materials within the core samples indicated that the slip zones have experienced temperatures of at least 400°C [ Mishima et al ., ], which is consistent with the temperatures obtained by using the compositions of major and trace elements (>350°C by Ishikawa et al []), inorganic carbon content (550°C by Hirono et al .…”

Section: Discussionmentioning

confidence: 99%

Vaporization of fault water during seismic slip

2017

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Laboratory and numerical studies, as well as field observations, indicate that phase transitions of pore water might be an important process in large earthquakes. We present a model of the thermo‐hydro‐chemo‐mechanical processes, including a two‐phase mixture model to incorporate the phase transitions of pore water, occurring during fast slip (i.e., a natural earthquake) in order to investigate the effects of vaporization on the coseismic slip. Using parameters from typical natural faults, our modeling shows that vaporization can indeed occur at the shallow depths of an earthquake, irrespective of the wide variability of the parameters involved (sliding velocity, friction coefficient, gouge permeability and porosity, and shear‐induced dilatancy). Due to the fast kinetics, water vaporization can cause a rapid slip weakening even when the hydrological conditions of the fault zone are not favorable for thermal pressurization, e.g., when permeability is high. At the same time, the latent heat associated with the phase transition causes the temperature rise in the slip zone to be buffered. Our parametric analyses reveal that the amount of frictional work is the principal factor controlling the onset and activity of vaporization and that it can easily be achieved in earthquakes. Our study shows that coseismic pore fluid vaporization might have played important roles at shallow depths of large earthquakes by enhancing slip weakening and buffering the temperature rise. The combined effects may provide an alternative explanation for the fact that low‐temperature anomalies were measured in the slip zones at shallow depths of large earthquakes.

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Analyses of pseudotachylyte from Hole-B of Taiwan Chelungpu Fault Drilling Project (TCDP); their implications for seismic slip behaviors during the 1999 Chi-Chi earthquake

Cited by 22 publications

References 64 publications

Co-seismic and/or a-seismic microstructures of JFAST 343 core samples from the Japan Trench

Co-seismic and/or a-seismic microstructures of JFAST 343 core samples from the Japan Trench

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

Vaporization of fault water during seismic slip

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