Mantle-derived helium released through the Japan trench bend-faults

Park, Jin-Oh; Takahata, Naoto; Hondori, Ehsan Jamali; Yamaguchi, Asuka; Kagoshima, Takanori; Tsuru, Takeshi Go; Fujie, Gou; Sun, Yue; Ashi, Juichiro; Yamano, Makoto; Sano, Yuji

doi:10.1038/s41598-021-91523-6

Cited by 3 publications

(1 citation statement)

References 51 publications

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“…We developed an initial P-wave interval velocity model by using the layer stripping approach 42 and further updated the velocity model using several iterations of grid-based traveltime tomography 43 . For the sake of computational efficiency, we applied Kirchhoff prestack depth migration 44 (KPSDM) during the velocity model building stage but after obtaining the final velocity model we applied reverse time migration 45 – 47 (RTM) to produce the seismic depth sections with the highest quality from the target area within 40–0 km distance toward the trench. Because RTM does not require any high-frequency approximation, has no dip restrictions, and can properly image multipath events the RTM images have a better quality and higher accuracy than KPSDM images (see Fig.…”

Section: Methodsmentioning

confidence: 99%

Connection between high pore-fluid pressure and frictional instability at tsunamigenic plate boundary fault of 2011 Tohoku-Oki earthquake

Hondori

Park

2022

Sci Rep

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The 2011 Tohoku-Oki earthquake (M 9.0) rupture propagated along a shallow plate boundary thrust fault (i.e. decollement) to the trench, displaced the seafloor, and triggered a devastating tsunami. Physical properties of the underthrust sediments which control the rupture propagation are yet poorly known. We use a 2D seismic dataset to build velocity model for imaging and apply reverse time migration. We then calculate pore-fluid pressure along the decollement as the top boundary of underthrust sediments, and along the backstop interface as the boundary between undeformed structures in the continental plate and the severely deformed sediments in the accretionary prism. The results show that within horizontal distance of 40–22 km toward the trench, pore-fluid pressure is 82–60% higher than the hydrostatic pressure for both decollement and backstop interface. It then reduces to hydrostatic level for the backstop interface but remains 60–40% higher than hydrostatic level for the decollement, causing frictional instability in favor of fault rupture along the decollement. We report for the first time, by our knowledge, detailed seismic images of fluid-rich trapped bucket sediments, quantitative stress states, and fluid drainage conditions at shallow tsunamigenic portion of the Japan Trench, which are consistent with the seafloor and borehole observations.

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Section: Methodsmentioning

confidence: 99%

Connection between high pore-fluid pressure and frictional instability at tsunamigenic plate boundary fault of 2011 Tohoku-Oki earthquake

Hondori

Park

2022

Sci Rep

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Tectonic deformation at the outer rise of subduction zones

Yang

Zhao

2022

Geophysical Journal International

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Summary Fluids associated with subducting slabs play a crucial role in regulating the dynamics of water discharge, subsequent arc magmatism, and intermediate-depth earthquakes in subduction zones. The incoming slab mantle hydration is primarily determined by deep normal faulting due to plate bending at the trench. However, the controlling factors on the outer rise faulting pattern, and the correlation between the inherited outer rise deformation and the intermediate-depth earthquakes, remain to be understood. Here we present high-resolution visco-elasto-plastic numerical models of free subduction for slab bending-related faulting prior to subduction. Our model results show that plastic weakening and friction coefficient of the slab mantle exhibit a significant impact on fault pattern, while plate age and elasticity have a minimal bearing for mature slabs. The brittle bending faults result in large positive pressure gradients in the vertical direction, facilitating seawater infiltrating into the subducting slabs, which corroborates previous numerical models. The faults reaching 15–30 km beneath the Moho coincide with the width of the double seismic zone in subduction zones. We anticipate that water pumped into the slab mantle along the faults, with decreasing water content along the depth, can explain the relatively sporadic lower plane earthquakes.

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Fault geometry of M6-class normal-faulting earthquakes in the outer trench slope of Japan Trench from ocean bottom seismograph observations

Obana

Takahashi

Yamamoto

et al. 2023

Prog Earth Planet Sci

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Since the 2011 Mw 9.0 Tohoku-oki earthquake, intra-plate normal-faulting earthquakes, including several M7-class earthquakes, have occurred in the outer trench slope area from the trench to the outer rise along the Japan Trench. Concerns regarding large earthquakes and associated tsunamis have also arisen. Based on aftershock distributions, several outer trench slope normal-faulting earthquakes (hereinafter referred to as outer-rise earthquakes) are likely related to the rupture of multiple faults. However, few observations have clearly shown how multiple faults act during outer-rise earthquakes. During the ocean bottom seismograph (OBS) observations in the outer trench slope area of the central Japan Trench from September 2017 to July 2018, three M6-class normal-faulting earthquakes (Mw 6.2 on September 20, Mw 6.2 on October 06, and Mw 6.0 on November 12) occurred around the OBS network. The near-field OBS observations provided detailed information on hypocenter locations and focal mechanisms of the mainshocks and aftershocks, including immediately after the mainshocks. We investigated the fault configurations of normal-faulting earthquakes based on OBS observations. During the September 2017 earthquake, the mainshock ruptured high-angle normal faults with a dip angle of 65°. Off-fault aftershock activities that were not directly related to the mainshock rupture and could be explained by the stress changes caused by the mainshock were confirmed. However, hypocenter distributions and focal mechanisms of the main and aftershocks of the October and November 2017 earthquakes suggest that the mainshock ruptured multiple faults with various dipping directions, angles, and strike orientations. The complicated fault geometry should be considered a possible fault model for large outer-rise earthquakes and related tsunamis.

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Mantle-derived helium released through the Japan trench bend-faults

Cited by 3 publications

References 51 publications

Connection between high pore-fluid pressure and frictional instability at tsunamigenic plate boundary fault of 2011 Tohoku-Oki earthquake

Connection between high pore-fluid pressure and frictional instability at tsunamigenic plate boundary fault of 2011 Tohoku-Oki earthquake

Tectonic deformation at the outer rise of subduction zones

Fault geometry of M6-class normal-faulting earthquakes in the outer trench slope of Japan Trench from ocean bottom seismograph observations

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