Runaway slip to the trench due to rupture of highly pressurized megathrust beneath the middle trench slope: The tsunamigenesis of the 2011 Tohoku earthquake off the east coast of northern Japan

Kimura, Gaku; Hina, Shoko; Hamada, Yohei; Kameda, J.; Tsuji, Takeshi; Kinoshita, Masataka; Yamaguchi, Asuka

doi:10.1016/j.epsl.2012.04.002

Cited by 94 publications

(106 citation statements)

References 62 publications

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“…However, a large depression has been recognized in the Kimura et al 2012). The slope surface is separated into four slopes by the tilt angle: the deep-sea terrace, the upper slope, the middle slope, and the lower slope.…”

Section: Tectonic Settingmentioning

confidence: 99%

“…Based on bathymetry changes from before to after the earthquake, Fujiwara et al (2011) demonstrated that the seafloor of the outermost part of the landward trench slope moved approximately 50 m toward the trench and was uplifted by approximately 7 to 10 m. The large fault rupture and propagation might have been due to the essentially weak fault material and dynamic weakening ) and/or abnormal fluid pressure along the megathrust (Kimura et al 2012). Fujie et al (2013) researched the along-trench variation of the structure with seismic surveys in the northern Japan Trench, and their data suggest that there is a good correlation between the seismic structure and segmentation of the interplate coupling.…”

Section: Introductionmentioning

confidence: 99%

“…The deformation and frictional properties (the effective coefficient of basal friction and pore fluid pressure ratio) beneath the forearc are the keys to elucidating this unusual event. Kimura et al (2012) focused on seismic reflection data along a seismic transect of the ruptured area at the Japan Trench, and they measured the taper angle and estimated the effective coefficient of basal friction at the plate boundary by using the critically tapered Coulomb wedge theory (Davis et al 1983;Dahlen 1984). However, a limited profile from the narrow area is not enough to understand the frictional properties of the plate boundary in comprehensive areas of the Japan Trench.…”

Section: Introductionmentioning

confidence: 99%

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Friction properties of the plate boundary megathrust beneath the frontal wedge near the Japan Trench: an inference from topographic variation

et al. 2014

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The 2011 Tohoku-Oki earthquake (Mw 9.0) produced a fault rupture that extended to the toe of the Japan Trench. The deformation and frictional properties beneath the forearc are keys that can help to elucidate this unusual event.In the present study, to investigate the frictional properties of the shallow part of the plate boundary, we applied the critically tapered Coulomb wedge theory to the Japan Trench and obtained the effective coefficient of basal friction μ ′ b À Áand Hubbert-Rubey pore fluid pressure ratio (λ) of the wedge beneath the lower slope. We extracted the surface slope angle and décollement dip angle (which are the necessary topographic parameters for applying the critical taper theory) from seismic reflection and refraction survey data at 12 sites in the frontal wedges of the Japan Trench. We found that the angle between the décollement and back-stop interface generally decreases toward the north. The measured taper angle and inferred effective friction coefficient were remarkably high at three locations. The southernmost area, which had the highest coefficient of basal friction, coincides with the area where the seamount is colliding offshore of Fukushima. The second area with a high effective coefficient of basal friction coincides with the maximum slip location during the 2011 Tohoku-Oki earthquake. The area of the 2011 earthquake rupture was topographically unique from other forearc regions in the Japan Trench. The strain energy accumulation near the trench axis may have proceeded because of the relatively high friction, and later this caused a large slip and collapse of the wedge. The location off Sanriku, where there are neither seamount collisions nor rupture propagation, also has a high coefficient of basal friction. The characteristics of the taper angle, effective coefficient of basal friction, and pore fluid pressure ratio along the Japan Trench presented herein may contribute to the understanding of the relationship between the geometry of the prism and the potential for generating seismo-tsunamigenic slips.

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Section: Tectonic Settingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Friction properties of the plate boundary megathrust beneath the frontal wedge near the Japan Trench: an inference from topographic variation

et al. 2014

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“…According to Kameda et al (2012), cataclastic deformation in this area would have been most pronounced once the transformation of opal to quartz had been completed. Kinetic modeling for siliceous oozes undergoing subduction into the Japan Trench indicates that the transformation of opal to quartz progresses actively at temperatures around 100°C along the plate interface Kimura et al, 2012), after which the siliceous deposits become crystalline cherts made up mostly of quartz. The analyzed chert may have experienced the transformation reaction of up to~220°C as inferred from vitrinite reflectance analyses of the accompanying terrigenous rocks .…”

Section: Concentrations Of Graphite and Clay In The Black Shear Zonesmentioning

confidence: 99%

“…Recently, we have focused on chert as an analog of the thick pelagic deposits that are being subducted into the Japan Trench Kimura et al, 2012), where disastrous events such as the 2011 Mw 9.0 Tohoku-oki earthquake occurred. The cherts characteristically contain several black shear zones, along which most of shear deformation in this exposure is localized.…”

Section: Introductionmentioning

confidence: 99%

The influence of organic–rich shear zones on pelagic sediment deformation and seismogenesis in a subduction zone

Kameda

Kouketsu

Shimizu

et al. 2014

Journal of Mineralogical and Petrological Sciences

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We have examined the mineralogy and deformation of black shear zones containing abundant carbonaceous materials (CM) and clay minerals in bedded ribbon cherts in a Jurassic accretionary complex, central Japan. Microtextural observations indicate that pressure solution and cataclastic deformation were the primary deformation mechanisms in the cherts. Whole-rock mineral compositions were quantitatively investigated using X-ray diffraction, Raman spectroscopy, and a CHN elemental analyzer. The results show that the samples contain variable amounts of CM and clay minerals, up to 17 wt% and 60 wt%, respectively. Moreover, the clay and CM contents in the samples, including the host rock cherts, show a positive correlation represented by a single compositional trend, and this may be explained by the progressive concentration of clays and CM due to pressure solution and the removal of soluble quartz or mass transfer processes associated with deformation. Intact cherts dominated by quartz seem to provide plausible source rocks for the nucleation of seismic slip including slow slip events, while the abundant CM and clays as observed in the black shear zones may have effectively weakened and stabilized the sliding behavior. These results are important for understanding deformation processes in the Japan Trench.

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Structural heterogeneities around the megathrust zone of the 2011 Tohoku earthquake from tomographic inversion of onshore and offshore seismic observations

Yamamoto

Obana

Kodaira

et al. 2014

J. Geophys. Res. Solid Earth

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We performed a three-dimensional seismic tomography around the coseismic slip area of the 2011 Tohoku earthquake. By combining data from the aftershock period collected by ocean bottom seismographs (OBSs), OBS data from previous studies off the Miyagi coast, and land seismic data, we modeled the detailed seismic velocity structure along the plate boundary from the Japan Trench to near the coastline. Our results indicate that V P , V S , and V P /V S along the plate boundary change drastically about 60 km landward from the trench axis. Trenchward of this boundary, velocities are consistent with a fluid-rich environment (low V P and V S and high V P /V S ) associated with the occurrence of sediment compaction and opal-to-quartz metamorphism. This area also corresponds to the contact between the slab and upper crust or between the slab and the sediment layer. A comparison of our results with numerical simulations and geological studies suggests that thermal pressurization might have occurred near the trench axis during the 2011 Tohoku earthquake. To the west of this boundary, where V P , V S , and V P /V S have moderate values, our model showed small-scale heterogeneous structures in the subducted oceanic crust near the hypocenter of the Tohoku earthquake with regions of low and high V P /V S on the updip and downdip sides of the hypocenter, respectively. We interpret the former as corresponding to the strong coupling patch and the latter as the localized fluid-rich zone. Small-scale heterogeneities thus may affect the nucleation and rupture processes of large earthquakes.

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Runaway slip to the trench due to rupture of highly pressurized megathrust beneath the middle trench slope: The tsunamigenesis of the 2011 Tohoku earthquake off the east coast of northern Japan

Cited by 94 publications

References 62 publications

Friction properties of the plate boundary megathrust beneath the frontal wedge near the Japan Trench: an inference from topographic variation

Friction properties of the plate boundary megathrust beneath the frontal wedge near the Japan Trench: an inference from topographic variation

The influence of organic–rich shear zones on pelagic sediment deformation and seismogenesis in a subduction zone

Structural heterogeneities around the megathrust zone of the 2011 Tohoku earthquake from tomographic inversion of onshore and offshore seismic observations

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