Syndeformational antigorite dehydration produces stable fault slip

Chernak, L. J.; Hirth, Greg

doi:10.1130/g31919.1

Cited by 61 publications

(61 citation statements)

References 27 publications

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“…During the test performed in creep conditions (at constant differential stress), no macroscopic fracture was observed. It is consistent with dehydration tests performed on serpentinite by Chernak and Hirth [2010, 2011], which do not bring any evidence of faulting. In perfectly drained conditions, dehydrating rocks do not undergo catastrophic embrittlement (e.g., stick‐slip); however, one fundamental characteristic is the important deformation allowed by porosity compaction.…”

Section: Extrapolations and Implications For Subduction Zonessupporting

confidence: 88%

Dehydration‐induced damage and deformation in gypsum and implications for subduction zone processes

et al. 2012

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[1] Experimental heating tests were performed on Volterra gypsum to study the micromechanical consequences of the dehydration reaction. The experimental conditions were drained at 5 MPa fluid pressure and confining pressures ranging from 15 to 55 MPa. One test was performed with a constantly applied differential stress of 30 MPa. The reaction is marked by (1) a porosity increase and homogeneous compaction, (2) a swarm of acoustic emissions, (3) a large decrease in P and S wave velocities, and (4) a decrease in V P /V S ratio. Wave velocity data are interpreted in terms of crack density and pore aspect ratio, which, modeling pores as spheroids, is estimated at around 0.05 (crack-like spheroid). Complementary tests performed in an environmental scanning electron microscope indicate that cracks first form inside the gypsum grains and are oriented preferentially along the crystal structure of gypsum. Most of the visible porosity appears at later stages when grains shrink and grain boundaries open. Extrapolation of our data to serpentinites in subduction zones suggest that the signature of dehydrating rocks in seismic tomography could be a low apparent Poisson's ratio, although this interpretation may be masked by anisotropy development due to preexisting crystal preferred orientation and/or deformation-induced cracking. The large compaction and the absence of strain localization in the deformation test suggests that dehydrating rocks maybe seen as soft inclusions and could thus induce ruptures in the surrounding, nonreacting rocks.Citation: Brantut, N., A. Schubnel, E. C. David, E. Héripré, Y. Guéguen, and A. Dimanov (2012), Dehydration-induced damage and deformation in gypsum and implications for subduction zone processes,

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Section: Extrapolations and Implications For Subduction Zonessupporting

confidence: 88%

Dehydration‐induced damage and deformation in gypsum and implications for subduction zone processes

et al. 2012

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“…According to analogue experiments examining slip behavior during faulting under undrained conditions [ Chernak and Hirth , ; Hilairet et al ., ], the relationship between slab dehydration and regular earthquakes remains ambiguous. However, these studies also insist that slow‐slip events might occur commonly under the conditions in which intermediate‐depth earthquakes occur [ Chernak and Hirth , ] or implicitly suggest that the viscous relaxation of serpentinite can trigger large earthquakes in subduction zones over interseismic periods of several years based on the low measured viscosity of serpentinite [ Hilairet et al ., ]. In addition, seismic tomography has revealed high V p / V s ratios and high Poisson's ratios at the base of the seismogenic zone [ Hyndman , ], along with elevated pore pressures estimated from low P ‐wave velocities in the source region of very low‐frequency events [ Kitajima and Saffer , ].…”

Section: Discussionmentioning

confidence: 99%

Three‐dimensional numerical modeling of thermal regime and slab dehydration beneath Kanto and Tohoku, Japan

Yoshioka

Manea

et al. 2017

JGR Solid Earth

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Although the thermal regime of the interface between two overlapping subducting plates, such as those beneath Kanto, Japan, is thought to play an important role in affecting the distribution of interplate and intraslab earthquakes, the estimation of the thermal regime remains challenging to date. We constructed a three‐dimensional (3‐D) thermal convection model to simulate the subduction of the Pacific plate along the Japan Trench and Izu‐Bonin Trench, including the subduction of the Philippine Sea beneath Kanto and investigated the slab thermal regime and slab water contents in this complex tectonic setting. Based on the subduction parameters tested in generic models with two flat oceanic plates, a faster or thicker plate subducting in a more trench‐normal direction produces a colder slab thermal regime. The interplate temperature of the cold anomaly beneath offshore Kanto was approximately 300°C colder than that beneath offshore Tohoku at a same depth of 40 km and approximately 600°C colder at a depth of 70 km. The convergence between the two subducting plates produces an asymmetric thermal structure in the slab contact zone beneath Kanto, which is characterized by clustered seismicity in the colder southwestern half. The thermo‐dehydration state of the mid‐ocean ridge basalt near the upper surface of the subducted Pacific plate controls the interplate seismicity beneath the Kanto‐Tohoku region according to the spatial concurrence of the thermo‐dehydration and seismicity along the megathrust fault zone of the subducted Pacific plate.

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“…Fault orientation, however, is more variable than observed in ice, although high angle (>40°) faults are observed in many samples [ Chernak and Hirth , ; Proctor and Hirth , ]. Failure is characterized by a partial stress drop and macroscale stable slip along the fault [ Chernak and Hirth , ; Proctor and Hirth , ]. Narrow, high‐angle faults lacking a concentration of microcracks near the main fault also have been observed in granite [ Shimada , ; Shimada and Cho , ; Tullis and Yund , ] and in olivine [ Schubnel et al ., ] deformed under high confinement, with terminal failure again characterized by partial stress drops.…”

Section: Character Of High‐confinement Brittle‐like Failurementioning

confidence: 99%

Strength‐limiting mechanisms in high‐confinement brittle‐like failure: Adiabatic transformational faulting

Renshaw

Schulson

2017

JGR Solid Earth

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Brittle‐like failure under high confinement impacts many geophysical phenomena, including earthquakes at depths beyond a few tens of kilometers. We reanalyze recent observations of high‐confinement brittle‐like failure of nominally thermodynamically stable ice and antigorite and show that the brittle‐like failure only occurs when the strain rate within an incipient adiabatic instability accelerates to the point that the attendant increase in localized temperature approaches a phase transition temperature, initiating transformational faulting. We test a closed‐form model for this process based on independently measureable parameters by comparing model predictions to observations of brittle‐like failure of ice and antigorite under high confinement. Model results do not constrain the mechanism of transformational faulting. However, the similarity of brittle‐like failure characteristics across a variety of geologic materials suggests a similarity of process. We propose that localized heating due to an adiabatic instability initiates dynamic recrystallization near the phase transformational temperature. Transformational superplasticity during recrystallization concentrates plastic strain ahead of the transformed region, causing dynamic recrystallization there and propagating slip in an autocatalytic manner. The newly recrystallized grains rapidly harden as strain accumulates, limiting the stress drop. As the recrystallized grains harden and the stress increases, localized heating reinitiates the adiabatic instability in the still warm region, concentrating plastic strain due to thermal softening and initiating another wave of dynamic recrystallization and partial stress drop. This process, termed adiabatic transformational faulting, could explain how deep earthquakes can propagate beyond the metastable wedge since the propagation of slip is due to dynamic recrystallization rather than to the primary phase transformation.

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Syndeformational antigorite dehydration produces stable fault slip

Cited by 61 publications

References 27 publications

Dehydration‐induced damage and deformation in gypsum and implications for subduction zone processes

Dehydration‐induced damage and deformation in gypsum and implications for subduction zone processes

Three‐dimensional numerical modeling of thermal regime and slab dehydration beneath Kanto and Tohoku, Japan

Strength‐limiting mechanisms in high‐confinement brittle‐like failure: Adiabatic transformational faulting

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