Generation of Pseudotachylyte by Ancient Seismic Faulting

Sibson, Richard H.

doi:10.1111/j.1365-246x.1975.tb06195.x

Cited by 740 publications

(581 citation statements)

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“…Field and laboratory studies have shown that pseudotachylites produced by frictional melting contribute to co-seismic weakening (Sibson, 1975;Goldsby and Tullis, 2002;Di Toro et al, 2004). The occurrence of glass textures in TCDP samples from Holes A and B clearly shows that frictional melting occurred.…”

Section: Amorphous Material/meltingmentioning

confidence: 96%

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: Amorphous Material/meltingmentioning

confidence: 96%

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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“…The minimum depth estimate of 2.2 + 1.0 km lies near the upper bound of the 1-15 km-depth range considered most appropriate for the generation of pseudotachylite by seismic faulting (Sibson 1975(Sibson , 1977. Certainly, the corrected age, even as a minimum value, is more in accord with the recent uplift history across the Alpine Fault than the K-Ar wholerock age of9.8 Ma obtained by Adams (1981) from a pseudotachylite vein in Harold Creek, 120 km along the fault zone to the northeast.…”

Section: Discussionmentioning

confidence: 79%

“…It has been suggested that pseudotachylites are the product of ultracomminution rather than fusion (Wenk 1978), but there is often good textural evidence for the former existence of a melt phase (Park 1961;Sibson 1975;Maddock 1983). In the Alpine Fault material, transmission electron miscroscopy (TEM) has revealed some surviving patches of glass, though devitrification to a chlorite-rich groundmass is generally well advanced (Sibson et al 1979; see also Wallace 1976).…”

Section: Introductionmentioning

confidence: 99%

Fission-track age for a pseudotachylite from the Alpine Fault Zone, New Zealand

Seward

Sibson

1985

New Zealand Journal of Geology and Geophysics

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The fission-track dating technique has been applied to glassy pseudotachylites from the Alpine Fault Zone of South Island, New Zealand. Of five samples investigated, only one proved sufficientlyglassy to be dated. It yielded a corrected age of 430 000 ± 100 000 years. From the Quaternary uplift rates across the fault zone, crude estimates suggest that the material was generated by slip at a depth of at least 2.2 ± 1.0 km.

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“…Pseudotachylite is thought by most to be the definitive record of 43 an earthquake where dynamic strength was controlled by shear melting [Jeffreys, 1942;44 McKenzie and Brune, 1972;Sibson, 1975] as we have assumed, and if the apparent stress,  a , is relatively small. For shear melting there are 156 no published proportions of radiated energy and heat from laboratory measurements.…”

Section: Field Observations and Melt Shear Strengthmentioning

confidence: 88%

“…A well-understood exception are the ancient earthquakes recorded in exhumed 42 pseudotachylites [Sibson, 1975]. Pseudotachylite is thought by most to be the definitive record of 43 an earthquake where dynamic strength was controlled by shear melting [Jeffreys, 1942;44 McKenzie and Brune, 1972;Sibson, 1975] as we have assumed, and if the apparent stress,  a , is relatively small.…”

Section: Field Observations and Melt Shear Strengthmentioning

confidence: 90%

Earthquake Source Properties from Pseudotachylite

Beeler

Toro

Nielsen

2016

Bulletin of the Seismological Society of America

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The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. and therefore related to stress drop. Except in a few notable cases, these displacements cannot be 5 easily related to the absolute stress level, the fault strength, or attributed to a particular physical 6 mechanism. In contrast paleo-earthquakes recorded by exhumed pseudotachylite have a known 7 dynamic mechanism whose properties constrain the co-seismic fault strength. Pseudotachylite 8 can be used to directly address a discrepancy between seismologically-measured stress drops, 9 which are typically a few MPa, and much larger dynamic stress drops expected from thermal 10 weakening during slip at seismic speeds in crystalline rock [Sibson, 1973; McKenzie and Brune, 11 1969;Lachenbruch, 1980; Mase and Smith, 1986;Rice, 2006], and as have been observed in 12 laboratory experiments at high slip rates [Di Toro et al., 2006a]. This note places 13 pseudotachylite-derived estimates of fault strength and inferred crustal stress within the context 14 and bounds of naturally observed earthquake source parameters: apparent stress, stress drop, and 15 overshoot, including consideration of fault surface roughness, off-fault damage, fracture energy, 16 and the 'strength excess'. The analysis, which assumes stress drop is related to corner frequency 17 by the Madariaga [1976] source model, is restricted to earthquakes of the Gole Larghe fault zone 18 in the Italian Alps where the dynamic shear strength is well-constrained by field and laboratory 19 measurements. We find that radiated energy is similar to or exceeds the shear-generated heat and 20 that the maximum strength excess is ~16 MPa. These events have inferred earthquake source 21 parameters that are rare, for instance a few percent of the global earthquake population has stress 22 drops as large, unless: fracture energy is routinely greater than in existing models, 23 pseudotachylite is not representative of the shear strength during the earthquake that generated it, 24 or unless the strength excess is larger than we have allowed. 25 nmb 311/14/16

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Generation of Pseudotachylyte by Ancient Seismic Faulting

Cited by 740 publications

References 29 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

Fission-track age for a pseudotachylite from the Alpine Fault Zone, New Zealand

Earthquake Source Properties from Pseudotachylite

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