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  • 1
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    Co-seismic frictional melting along an out-of-sequence thrust in the Shimanto accretionary complex. Implications on the tsunamigenic potential of splay faults in modern subduction zones (2006)
    In:  Earth planet. Sci. Lett., Dordrecht, Netherlands, Dr. W. Junk, vol. 245, no. 1-2, pp. 330-343, pp. L08304, (ISSN: 1340-4202)
    Details
    Publication Date: 2006
    Keywords: Friction ; Earthquake ; Geothermics ; Japan ; Subduction zone ; Tsunami(s) ; Stress ; EPSL ; paleogeothermal ; structure ; vitrinite ; reflectance ; fault ; rocks ; pseudotachylyte
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    BIBLIOGRAPHY SEISMOLOGY
  • 2
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    Thermal conductivities under high pressure in core samples from IODP NanTroSEIZE drilling site C0001 (2011)
    Wiley
    Details
    Publication Date: 2011-06-24
    Description: We examined the effects of high pressure on thermal conductivity in core samples from the slope–apron facies and the upper part of the accretionary prism at site C0001 of the NanTroSEIZE drilling program and in other samples of five terrestrial rock types. Thermal conductivity clearly increased with increasing pressure for both wet (water saturated) and dry samples. We determined the rate of thermal conductivity change of the NanTroSEIZE sediments to be 0.014 Wm−1K−1/MPa when pressure was increased, and 0.01 Wm−1K−1/MPa when pressure was decreased. Using the rate determined for decreasing pressure, we estimated that thermal conductivities measured at atmospheric pressure rather than at in situ pressure may be underestimated by 7% for a core sample from around 1 km depth and by 20% for a core sample from around 3 km depth. In general, the rate of thermal conductivity change with pressure showed a positive correlation with porosity. However, the relationship of the rate of thermal conductivity change to porosity is also dependent on the fabric, mineral composition, and pore structure of the sediments and rocks. Furthermore, for two sandstones we tested, the effect of pressure on thermal conductivity for dry samples was greater than that for wet samples.
    Electronic ISSN: 1525-2027
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 3
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    Velocity dependence of shear-induced permeability associated with frictional behavior in fault zones of the Nankai subduction zone (2012)
    Wiley
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    Publication Date: 2012-05-08
    Description: We measured frictional properties and permeability of core materials from the megasplay fault zone (site C0004) and the frontal thrust (site C0007) in the shallow part of the Nankai subduction zone. Permeability was measured before and after 7.9 m slip displacement at high (1.05 m/s) and low velocities (0.013 m/s) under normal stresses of 1.5 MPa using the rotary-shear apparatus, from which we estimated the shear-induced permeability change in an experimental fault gouge prepared from core material. Gouge permeability (10−18 m2) decreased after sliding for wet gouge and increased for dry gouge. The high-velocity friction test under wet conditions yielded a smaller reduction in permeability than the low-velocity test, whereas the opposite trend was observed in dry conditions. We attribute the differences in permeability to the effects of thermal/mechanical pore pressurization upon shear-induced compaction. Symmetric boudin structures may represent evidence of hydrofracturing induced by pore fluid pressurization. The large friction coefficient of the megasplay fault material in the slow and wet friction tests is explained by homogeneous shear deformation and higher permeability that promotes faster shear-induced compaction. The similarity in post-shear permeability for the gouges from the both faults may account for the similar friction coefficients in high-velocity friction, assuming that the pore fluid pressurization process controls high-velocity frictional behavior. This velocity dependence on friction suggests that a large dynamic stress drop is expected for the megasplay fault, implying that large slip displacement followed by a giant tsunami is plausible when a rupture from depth propagates to the megasplay fault.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 4
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    Geochemical signals for determining the slip-weakening mechanism of an ancient megasplay fault in the Shimanto accretionary complex (2011)
    Wiley
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    Publication Date: 2011-03-30
    Description: To investigate the slip behavior of a megasplay fault branching from a subduction boundary megathrust, we investigated the geochemistry of an out-of-sequence thrust that formed at 2.5–5.5 km depth. Rocks from the slip zone show major-element and fluid-immobile trace-element compositions that are consistent with disequilibrium flash melting. Distinct depletions of Li, Rb, and Cs in the slip-zone rocks indicate fluid–rock interactions at high temperatures (〉350°C). These findings suggest a slip process in which high-temperature pore fluids were generated by frictional slip, but the thermally-enhanced pressure might not have reached a sufficient level to cause thermal pressurization, and the temperature continued to increase to attain melting of mica minerals. Comparison with slip zone that formed at a shallower depth (1–2 km), where only thermal pressurization occurred, suggests a transition from melt lubrication at depth to thermal pressurization at shallower depths along a megasplay faults.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 5
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    Permeability changes in simulated granite faults during and after frictional sliding (2014)
    Wiley
    In: Geofluids
    Details
    Publication Date: 2014-05-31
    Description: Thermal–hydrological–mechanical coupling processes suggest that fault permeability should undergo dynamic change as a result of seismic slip. In igneous rocks, a fault's slip surface may have much higher permeability than the surrounding rock matrix and therefore operate as a conduit for fluids. We conducted laboratory experiments to investigate changes in fracture permeability (or transmissivity) of a fault in granite due to shear slip and cyclic heating and cooling. Our experiments showed that high initial fracture transmissivity (〉10 –18 m 3 ) was associated with a high friction coefficient and that transmissivity decreased during slip. We propose that this reduction in transmissivity reflects the presence of gouge in fracture voids, increasing the area of contact in the fault plane and reducing the hydraulic aperture. In contrast, when initial fracture transmissivity was low (〈10 –18 m 3 ), we observed that friction was lower and transmissivity increased during slip. The high transmissivity and high friction may be explained by large areas of bare rock being in contact on the slip surface. Slip velocity had little influence on the evolution of permeability, probably because gouge produced at different slip velocities had similar grain size distributions, or because gouge leaked from the slip surface. Transmissivity decreased with increasing temperature in heating tests, probably due to thermal expansion increasing normal stress on the fracture. Frictional heating did not influence transmissivity during the shearing tests. This article is protected by copyright. All rights reserved.
    Print ISSN: 1468-8115
    Electronic ISSN: 1468-8123
    Topics: Geosciences
    Published by Wiley
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  • 6
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    Estimation of slip parameters associated with frictional heating during the 1999 Taiwan Chi-Chi earthquake by vitrinite reflectance geothermometry (2014)
    SpringerOpen
    Details
    Publication Date: 2014-05-02
    Description: To estimate the slip parameters and understand the fault lubrication mechanism during the 1999 Taiwan Chi-Chi earthquake, we applied vitrinite reflectance geothermometry to samples retrieved from the Chelungpu fault. We found a marked reflectance anomaly of 1.30% +/- 0.21% in the primary slip zone of the earthquake, whereas the reflectances in the surrounding deformed and host rocks were 0.45% to 0.77%. By applying a kinetic model of vitrinite thermal maturation together with a one-dimensional heat and thermal diffusion equation, we determined the shear stress and peak temperature in the slip zone during the earthquake to be 1.00 +/- 0.04 MPa and 626[degree sign]C +/- 25[degree sign]C, respectively. Taking into account the probable overestimation of the temperature owing to a mechanochemically enhanced reaction or flash heating at grain contacts, this temperature should be considered an upper limit. The lower limit was previously constrained to 400[degree sign]C by studies of fluid-mobile trace-element concentrations and magnetic minerals. Therefore, we inferred that the peak temperature during the Chi-Chi earthquake was 400[degree sign]C to 626[degree sign]C, corresponding to an apparent friction coefficient of 0.01 to 0.06. Such low friction and the previous evidence of a high-temperature fluid suggest that thermal pressurization likely contributed to dynamic weakening during the Chi-Chi earthquake.
    Print ISSN: 1343-8832
    Electronic ISSN: 1880-5981
    Topics: Geosciences
    Published by SpringerOpen
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  • 7
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    Pressure dependence of fluid transport properties of shallow fault systems in the Nankai subduction zone (2014)
    SpringerOpen
    Details
    Publication Date: 2014-08-14
    Description: We measured fluid transport properties at an effective pressure of 40 MPa in core samples of sediments and fault rocks collected by the Integrated Ocean Drilling Program (IODP) NanTroSEIZE drilling project Expedition 316 from the megasplay fault system (site C0004) and the frontal thrust (site C0007) in the Nankai subduction zone. Permeability decreased with effective pressure as a power law function. Permeability values in the fault zones were 8 x 10-18 m2 at site C0004 and 9 x 10-18 m2 at site C0007. Stratigraphic variation in transport properties suggests that the megasplay fault zone may act as a barrier to fluid flow, but the frontal thrust fault zone might not. Depth variation in permeability at site C0007 is probably controlled by the mechanical compaction of sediment. Hydraulic diffusivity at shallow depths was approximately 1 x 10-6 m2 s-1 in both fault zones, which is small enough to lead to pore pressure generation that can cause dynamic fault weakening. However, absence of a very low permeable zone, which may have formed in the Japan Trench subduction zone, might prevent facilitation of huge shallow slips during Nankai subduction zone earthquakes. Porosity tests under dry conditions might have overestimated the porosity.
    Print ISSN: 1343-8832
    Electronic ISSN: 1880-5981
    Topics: Geosciences
    Published by SpringerOpen
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  • 8
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    Frictional melting of clayey gouge during seismic fault slip: Experimental observation and implications (2014)
    Wiley
    Details
    Publication Date: 2014-07-31
    Description: Clayey gouges are common in fault slip zones at shallow depths. Thus, the fault zone processes and frictional behaviors of the gouges are critical to understanding seismic slip at these depths. We conducted rotary shear tests on clayey gouge (~41 wt.% clay minerals) at a seismic slip rate of 1.3 m/s. Here, we report that the gouge was melted at 5 MPa of normal stress and room-humidity conditions. The initial local melting was followed by melt layer formation. Clay minerals (e.g., smectite and illite) and plagioclase were melted and quenched to glass with numerous vesicles. Both flash heating and bulk temperature increases appear to be responsible for the melting. This observation of clayey gouge melting is comparable to that of natural faults (e.g., Chelungpu fault, Taiwan). Due to heterogeneous fault zone properties (e.g., permeability), frictional melting may be one of the important processes in clayey slip zones at shallow depths.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 9
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    Coal maturation by frictional heat during rapid fault slip (2012)
    Wiley
    Details
    Publication Date: 2012-08-16
    Description: The detection of frictional heating effects along faults provides key insight into the dynamics of earthquakes and faulting. Thermal maturity of organic matter has been considered a possible fault-thermometer that records the frictional heat signature of ancient earthquakes. However, whether or not organic matter can mature on the order of seconds, typical earthquake rise time, remains uncertain. Here we present the results of experiments aimed at revealing coal maturation by frictional heat generated at slip velocities representative of natural earthquakes of up to 1.3 m/s. Our results show that coal can mature coseismically in ∼11 seconds at temperatures induced by frictional heat ranging from 26 to 266°C. Even with a temperature rise to only 28.7°C over 15 m displacement in ∼3.2 hours, coal can slightly mature within a shear localized zone. The commonly used kinetic model of vitrinite maturation cannot predict the experimental results. A kinetic model involving the effect of flash temperature at grain contacts and mechanochemical effects on reaction kinetics is necessary to better estimate heat generation along a fault.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 10
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    Slip parameters on major thrusts at a convergent plate boundary: regional heterogeneity of potential slip distance at the shallow portion of the subducting plate (2018)
    SpringerOpen
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    Publication Date: 2018-03-12
    Description: Understanding variations of slip distance along major thrust systems at convergent margins is an important issue for evaluation of near-trench slip and the potential generation of large tsunamis. We derived qu...
    Print ISSN: 1343-8832
    Electronic ISSN: 1880-5981
    Topics: Geosciences
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