Catastrophic emplacement of giant landslides aided by thermal decomposition: Heart Mountain, Wyoming

Mitchell, Thomas M.; Smith, Steven A.; Anders, Mark H.; Toro, Giulio Di; Nielsen, S. B.; Cavallo, Andrea; Beard, Andy

doi:10.1016/j.epsl.2014.10.051

Cited by 78 publications

(58 citation statements)

References 39 publications

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“…First, we predict the maximum temperature during an earthquake—or other rapid slip events such as landslides where thermal decomposition might be triggered [ Mitchell et al , ]—using equation . We use the parameters from Tables and , and a heating rate of

τ \overset{γ}{true} = 252

MPa/ms.…”

Section: Predictions For Other Common Fault Materialsmentioning

confidence: 62%

Strain localization driven by thermal decomposition during seismic shear

2015

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Field and laboratory observations show that shear deformation is often extremely localized at seismic slip rates, with a typical deforming zone width on the order of a few tens of microns. This extreme localization can be understood in terms of thermally driven weakening mechanisms. A zone of initially high strain rate will experience more shear heating and thus weaken faster, making it more likely to accommodate subsequent deformation. Fault zones often contain thermally unstable minerals such as clays or carbonates, which devolatilize at the high temperatures attained during seismic slip. In this paper, we investigate how these thermal decomposition reactions drive strain localization when coupled to a model for thermal pressurization of in situ groundwater. Building on Rice et al. (2014), we use a linear stability analysis to predict a localized zone thickness that depends on a combination of hydraulic, frictional, and thermochemical properties of the deforming fault rock. Numerical simulations show that the onset of thermal decomposition drives additional strain localization when compared with thermal pressurization alone and predict localized zone thicknesses of ∼7 and ∼13 μm for lizardite and calcite, respectively. Finally we show how thermal diffusion and the endothermic reaction combine to limit the peak temperature of the fault and that the pore fluid released by the reaction provides additional weakening of ∼20-40% of the initial strength.

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τ \overset{γ}{true} = 252

MPa/ms.…”

Section: Predictions For Other Common Fault Materialsmentioning

confidence: 62%

Strain localization driven by thermal decomposition during seismic shear

2015

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“…[] and more recently Mitchell et al . [] showed CO 2 degassing after only a few hundred microns of slip suggesting that flash heating was occurring. In higher normal‐stress experiments (8.5 MPa), Smith et al .…”

Section: Discussionmentioning

confidence: 99%

Dynamic weakening of serpentinite gouges and bare surfaces at seismic slip rates

et al. 2014

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To investigate differences in the frictional behavior between initially bare rock surfaces of serpentinite and powdered serpentinite (“gouge”) at subseismic to seismic slip rates, we conducted single-velocity step and multiple-velocity step friction experiments on an antigorite-rich and lizardite-rich serpentinite at slip rates (V) from 0.003 m/s to 6.5 m/s, sliding displacements up to 1.6 m, and normal stresses (σn) up to 22 MPa for gouge and 97 MPa for bare surfaces. Nominal steady state friction values (μnss) in gouge at V = 1 m/s are larger than in bare surfaces for all σn tested and demonstrate a strong σn dependence; μnss decreased from 0.51 at 4.0 MPa to 0.39 at 22.4 MPa. Conversely, μnss values for bare surfaces remained ∼0.1 with increasing σn and V. Additionally, the velocity at the onset of frictional weakening and the amount of slip prior to weakening were orders of magnitude larger in gouge than in bare surfaces. Extrapolation of the normal stress dependence for μnss suggests that the behavior of antigorite gouge approaches that of bare surfaces at σn ≥ 60 MPa. X-ray diffraction revealed dehydration reaction products in samples that frictionally weakened. Microstructural analysis revealed highly localized slip zones with melt-like textures in some cases gouge experiments and in all bare surfaces experiments for V ≥ 1 m/s. One-dimensional thermal modeling indicates that flash heating causes frictional weakening in both bare surfaces and gouge. Friction values for gouge decrease at higher velocities and after longer displacements than bare surfaces because strain is more distributed.Key PointsGouge friction approaches that of bare surfaces at high normal stressDehydration reactions and bulk melting in serpentinite in < 1 m of slipFlash heating causes dynamic frictional weakening in gouge and bare surfaces

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“…Laminated slip zones in the ultracataclasite of the Punchbowl fault have also been interpreted to develop by progressive wear and accumulation (Chester et al, ), which is consistent with our observations that the inferred older laminae show increasing density and decreasing porosity. In carbonate and clay gouges, very fine‐grained localized slip zones have been interpreted to form as a result of extreme particle size reduction and additional chemical decomposition (e.g., Brantut et al, ; Paola et al, ; Han et al, ; Green et al, ; Mitchell et al, ). Our calculations of localized slip zone thickness and energy dissipation indicate that cataclastic deformation plays a significant, if not dominant, role in mechanical energy dissipation of clay‐rich gouges and slip zone thickness.…”

Section: Lithologic Controls Of Slip Localizationmentioning

confidence: 99%

Localized Slip and Associated Fluidized Structures Record Seismic Slip in Clay‐Rich Fault Gouge

French

Chester

2018

JGR Solid Earth

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Fault rocks can weaken dramatically with increasing slip rate, which results in localization of slip and earthquakes. Exhumed fault zones and fault rocks deformed at seismic rates in the laboratory both show that deformation can become extremely localized to zones less than or equal to millimeters thick. However, localization can occur during aseismic slip, so evidence of localization cannot necessarily be interpreted as having occurred coseismically. Dynamic weakening that occurs during earthquakes is the result of processes that are unique to seismic slip rates, and previous results from carbonates show that these processes produce unique microstructures. We evaluate whether coseismic deformation at low normal stress produces unique structures within the localized slip zones and adjacent gouge that develop in clay‐rich gouge from the Central Deforming Zone of the San Andreas fault. We measured the thickness and orientations of localized slip zones and their internal lamina, particle orientations, and particle size distributions of gouge sheared from 0.35 to 1.3 m/s velocity, up to 25‐m displacement, and 1‐MPa normal stress, under water‐wet and room‐dry conditions. We find that the thicknesses of localized slip zones and their internal laminae are consistent with numerical formulations for thermal pressurization in wet gouge and both thermal decomposition and cataclastic deformation in dry gouge. Localized zones form coincident with a zone of fluidized gouge that accommodates at most 10% of the shear strain. We conclude that the combined occurrence of foliated localized shear zones with a zone of fluidized gouge may provide a record of seismicity in clay‐rich gouges.

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Catastrophic emplacement of giant landslides aided by thermal decomposition: Heart Mountain, Wyoming

Cited by 78 publications

References 39 publications

Strain localization driven by thermal decomposition during seismic shear

Strain localization driven by thermal decomposition during seismic shear

Dynamic weakening of serpentinite gouges and bare surfaces at seismic slip rates

Localized Slip and Associated Fluidized Structures Record Seismic Slip in Clay‐Rich Fault Gouge

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