Physical mechanisms of oceanic mantle earthquakes: Comparison of natural and experimental events

Kita, S.; Ferrand, Thomas P.

doi:10.1038/s41598-018-35290-x

Cited by 41 publications

(38 citation statements)

References 65 publications

(100 reference statements)

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“…Large and small earthquakes present striking similarities (e.g. Kita & Ferrand, 2018;Ide, 2019;Brodsky, 2019) and appear to nucleate similarly (Ide, 2019;Abercrombie, 2019), which supports that laboratory analogues (e.g. Mw -6, fault = 1mm; Ferrand et al, 2017) may be representative of natural processes (e.g.…”

Section: Accepted Articlesupporting

confidence: 54%

Scaling seismic fault thickness from the laboratory to the field

Ferrand

Nielsen

Labrousse

et al. 2021

Preprint

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Pseudotachylytes originate from the solidification of frictional melt, which transiently forms and lubricates the fault plane during an earthquake. Here we observe how the pseudotachylyte thickness a scales with the relative displacement D both at the laboratory and field scales, for measured slip varying from microns to meters, over six orders of magnitude. Considering all the data jointly, a bend appears in the scaling relationship when slip and thickness reach &#8764;1 mm and 100 &#181;m, respectively, i.e. MW > 1. This bend can be attributed to the melt thickness reaching a steady&#8208;state value due to melting dynamics under shear heating, as is suggested by the solution of a Stefan problem with a migrating boundary. Each increment of fault is heating up due to fast shearing near the rupture tip and starting cooling by thermal diffusion upon rupture. The building and sustainability of a connected melt layer depends on this energy balance. For plurimillimetric thicknesses (a > 1 mm), melt thickness growth reflects in first approximation the rate of shear heating which appears to decay in D&#8722;1/2 to D&#8722;1, likely due to melt lubrication controlled by melt + solid suspension viscosity and mobility. The pseudotachylyte thickness scales with moment M0 and magnitude MW; therefore, thickness alone may be used to estimate magnitude on fossil faults in the field in the absence of displacement markers within a reasonable error margin.

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Section: Accepted Articlesupporting

confidence: 54%

Scaling seismic fault thickness from the laboratory to the field

Ferrand

Nielsen

Labrousse

et al. 2021

Preprint

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“…Previous studies have found large b value anomalies near the top of some slab segments (Katsumata, ; van Stiphout et al, ; Wiemer & Benoit, ; Wyss et al, ); our results suggest that these differences are systematic, may be controlled by a few physical parameters, and are a global feature. Recent work in Japan (Kita & Ferrand, ) show larger b values in Hokkaido along the USL but have lower b values in the Tohoku area. Our results do not have the resolution to be able to compare each segment but point toward a global systematic behavior of b values between USL and LSL.…”

Section: Frequency‐magnitude Statisticsmentioning

confidence: 90%

Controlling Factors of Seismicity and Geometry in Double Seismic Zones

Florez

Prieto

2019

Geophysical Research Letters

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Double seismic zones are ubiquitous features of subduction zones, where seismicity is distributed along two layers separated by a region with significantly less seismic activity. Dehydration embrittlement is thought to be responsible for earthquakes in the subducting crust (upper layer), but the case for it in the lithospheric mantle (lower layer) is less clear. We apply a recently developed relative relocation technique to characterize seismicity in 32 slab segments. The high‐precision hypocentral depths allow us to assign events to either the upper or lower layer and to separately estimate frequency size distributions for each plane. We find consistently larger b values, correlating with slab age, for the upper layer and roughly constant values for the lower. We also show that thermal parameter and plate age are the key controls on double seismic zone geometry. Our results point to a relatively dry lower layer and suggest a fundamentally different mechanism for lithospheric mantle earthquakes.

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“…The microfractures are likely precursors of the mesoscale fractures. These dehydration reactions indicate that high INTRODUCTION High-pressure (HP) brittle deformation of subducting slabs has recently drawn increasing attention through petrological (e.g., Angiboust et al, 2012;Scambelluri et al, 2017;Behr et al, 2018), experimental (e.g., Okazaki and Hirth, 2016;Ferrand et al, 2017) and geophysical investigations (e.g., Kita and Ferrand, 2018;Florez and Prieto, 2019). HP brittle deformation is often correlated to an important facies change from blueschist to eclogite as it is coupled with significant metamorphic dehydration reactions (Peacock, 1993;Gao and Klemd, 2001;Hacker et al, 2003;Austrheim and Andersen, 2004).…”

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confidence: 99%

Brittle Deformation During Eclogitization of Early Paleozoic Blueschist

et al. 2020

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The Tsäkkok Lens of the Scandinavian Caledonides represents the outermost Baltican margin that was subducted in late Cambrian/Early Ordovician time during closure of the Iapetus Ocean. The lens predominantly consists of metasedimentary rocks hosting eclogite bodies that preserve brittle deformation on the μm-to-m scale. Here, we present a multidisciplinary approach that reveals fracturing related to dehydration and eclogitization of blueschists. Evidence for dehydration is provided by relic glaucophane and polyphase inclusions in garnet consisting of clinozoisite + quartz ± kyanite ± paragonite that are interpreted as lawsonite pseudomorphs. X-Ray chemical mapping of garnet shows a network of microchannels that propagate outward from polyphase inclusions. These microchannels are healed by garnet with elevated Mg relative to the surrounding garnet. Electron backscatter diffraction mapping revealed that Mg-rich microchannels are also delimited by low angle (<3°) boundaries. X-ray computed microtomography demonstrates that some garnet is transected by up to 300 μm wide microfractures that are sealed by omphacite ± quartz ± phengite. Locally, mesofractures sealed either by garnet- or omphacite-dominated veins transect through the eclogites. The interstices within the garnet veins are filled with omphacite + quartz + rutile + glaucophane ± phengite. In contrast, omphacite veins are predominantly composed of omphacite with minor apatite + quartz. Omphacite grains are elongated along [001] crystal axis and are preferably oriented orthogonal to the vein walls, indicating crystallization during fracture dilation. Conventional geothermobarometry using omphacite, phengite and garnet adjacent to fractures, provides pressure-temperature conditions of 2.47 ± 0.32 GPa and 620 ± 60°C for eclogites. The same method applied to a mesoscale garnet vein yields 2.42 ± 0.32 GPa at 635 ± 60°C. Zirconium-in-rutile thermometry applied to the same garnet vein provides a temperature of ∼620°C. Altogether, the microchannels, microfractures and mesofractures represent migration pathways for fluids that were produced during glaucophane and lawsonite breakdown. The microfractures are likely precursors of the mesoscale fractures. These dehydration reactions indicate that high pore-fluid pressure was a crucial factor for fracturing. Brittle failure of the eclogites thus represents a mechanism for fluid-escape in high-pressure conditions. These features may be directly associated with seismic events in a cold subduction regime.

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Physical mechanisms of oceanic mantle earthquakes: Comparison of natural and experimental events

Cited by 41 publications

References 65 publications

Scaling seismic fault thickness from the laboratory to the field

Scaling seismic fault thickness from the laboratory to the field

Controlling Factors of Seismicity and Geometry in Double Seismic Zones

Brittle Deformation During Eclogitization of Early Paleozoic Blueschist

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