Impulsive Tsunami and Large Runup Along the Sanriku Coast of Japan Produced by an Inelastic Wedge Deformation Model

Du, Yue; Ma, Shuo; Kubota, Tatsuya; Saito, Tatsuhiko

doi:10.1029/2021jb022098

Cited by 10 publications

(5 citation statements)

References 44 publications

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“…Inelastic deformation promotes seafloor uplift, decreases fault slip, and absorbs high-frequency seismic energy, thereby providing an effective mechanism for reconciling the divergence in observations of tsunami earthquakes 26 . Thus, inelastic wedge deformation has been suggested as the cause of the puzzling large run-up along the Sanriku coast during the 2011 Tohoku–Oki earthquake 28 . The results of our study provide direct evidence of the dominant effect of inelastic deformation in the coseismic deformation of the frontal prism, which highlights the substantial oversimplification of the prevailing elastic dominant deformation model in the outer-wedge region.…”

Section: Discussionmentioning

confidence: 99%

“…When extruded by the hard backstop, the sediments deform plastically and absorb seismic energy strongly 25,26 . Consequently, a trenchward increase of the seafloor uplift trend coupled with a trenchward slip tapering pattern can be produced under an inelastic model 27,28 . The inelastic deformation of the frontal prism decreases the shallow megathrust slip but converts the rupture energy into the uplift efficiently, which enhances the local tsunami size.…”

Section: Near-trench Coseismic Deformation Patternmentioning

confidence: 99%

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Complex tsunamigenic near-trench seafloor deformation during the 2011 Tohoku–Oki earthquake

et al. 2023

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The near-trench coseismic rupture behaviour of the 2011 Tohoku–Oki earthquake remains poorly understood due to the scarcity of near-field observations. Differential bathymetry offers a unique approach to studying offshore coseismic seafloor deformation but has a limited horizontal resolution. Here we use differential bathymetry estimates with improved horizontal resolutions to investigate near-trench coseismic slip behaviours in the 2011 Tohoku–Oki earthquake. In the main rupture region, a velocity-strengthening behaviour in the shallow fault is observed. By contrast, the seafloor uplift decreases towards the trench, but the trend inverts near the backstop interface outcrop, revealing significant off-fault deformation features. Amongst various competing off-fault effects observed, we suggest that inelastic deformation plays a predominant role in near-trench tsunami excitation. Large trench-bleaching rupture is also observed immediately north of 39°, delimiting the northern extent of the main rupture region. Overall, striking spatial heterogeneity of the shallow rupture behaviour is revealed for the region.

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Section: Discussionmentioning

confidence: 99%

Section: Near-trench Coseismic Deformation Patternmentioning

confidence: 99%

Complex tsunamigenic near-trench seafloor deformation during the 2011 Tohoku–Oki earthquake

et al. 2023

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“…It is well known that the largest runups in the 2011 Tohoku‐oki earthquake occurred north of 39°N, not in the region of main rupture (Figure S4 in Supporting Information S1) (Mori et al., 2011). The source for the largest runup in the north is still not fully understood (Kodaira et al., 2021), although some efforts have been made to explain it (e.g., Du et al., 2021; Satake et al., 2013; Yamazaki et al., 2018). We neither are in a position to tackle this scientific mystery.…”

Section: Discussionmentioning

confidence: 99%

Evaluating the Tsunamigenic Potential of Buried Versus Trench‐Breaching Megathrust Slip

et al. 2022

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Subduction megathrust ruptures that breach the trench, such as in the 2011 M = 9 Tohoku‐oki earthquake, can be very tsunamigenic. However, whether buried ruptures are intrinsically less tsunamigenic has not been fully investigated. Here, we conduct this investigation by studying the mechanics of seafloor deformation and the resultant tsunami runup. With a trench‐breaching rupture, deformation is dominated by the rigid‐body translation of the frontal upper plate, and seafloor uplift is enhanced by the horizontal motion of the sloping seafloor. With a buried rupture, the rigid‐body motion is reduced, but the shortening of the upper plate due to seaward slip termination causes elastic thickening to enhance tsunamigenic seafloor uplift. By combining a finite‐element deformation model and a shallow‐water equation tsunami model, we systematically test various subduction zone geometrical and slip parameters to study the trade‐off between rigid‐body translation and elastic thickening in causing seafloor uplift and tsunami runup. To isolate the effect of slip depth, we compare scenarios with the same peak slip and rupture width. We find that very shallow ruptures, including those breaching the trench, are generally less tsunamigenic than deeper ruptures. Given peak slip, tsunamigenic potential is maximized if the rupture is not too shallow or too deep but is buried to moderate depths. Our model tests using variable hypothetical rupture depths suggest that, with a slip magnitude as large as in the 2011 Tohoku‐oki earthquake, tsunami runups as high as the observed would occur even if the rupture were fully buried.

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“…For example, geodetic models tend to have smooth slip distributions with their peak slip patch located near the hypocentral region (Lay, 2018). Models using tsunami data may be influenced by secondary sources, including inelastic offfault deformation and possible submarine landslides (Uchida & Bürgmann, 2021;Kodaira et al, 2021;Du et al, 2021). However, tsunami data has an advantage over onshore observations due to its sensitivity to slip near the trench (Lay, 2018;Kodaira et al, 2021).…”

Section: Model Comparisonmentioning

confidence: 99%

“…For example, maximum slip estimates at the trench range from 0 to 80 m for an along-dip cross-section through the hypocenter of 45 published models (Sun et al, 2017). Similar variability exists along the strike direction, particularly regarding the northern rupture extent beyond 39.5 • N. This leaves the source of the Sanriku region tsunami a topic under debate (Mori et al, 2011;Kodaira et al, 2020;Du et al, 2021). The discrepancies among the finite-fault models of the Tohoku-Oki earthquake have given rise to several unresolved questions, including on tsunami sources and variability in megathrust frictional behavior (Tajima et al, 2013;Sun et al, 2017;Lay, 2018;Kodaira et al, 2020;Uchida & Bürgmann, 2021).…”

Section: Introductionmentioning

confidence: 97%

A quantitative comparison and validation of finite-fault models: The 2011 Tohoku-Oki earthquake

Wong

Fan

Gabriel

2023

Preprint

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Large earthquakes rupture faults over hundreds of kilometers within minutes. Finite-fault models elucidate these processes and provide observational constraints for understanding earthquake physics. However, finite-fault inversions are subject to non-uniqueness and substantial uncertainties. The diverse range of published models for the well-recorded 2011 M_w 9.0 Tohoku-Oki earthquake aptly illustrates this issue, and details of its rupture process remain under debate. Here, we comprehensively compare 32 finite-fault models of the Tohoku-Oki earthquake and analyze the sensitivity of three commonly-used observational data types (geodetic, seismic, and tsunami) to the slip features identified. We first project all models to a realistic megathrust geometry and a 1-km subfault size. At this scale, we observe poor correlation among the models, irrespective of the data type. However, model agreement improves significantly when subfault sizes are increased, implying that their differences primarily stem from small-scale features. We then forward-compute geodetic and teleseismic synthetics and compare them with observations. We find that seismic observations are sensitive to rupture propagation, such as the peak-slip-rise time. However, neither teleseismic nor geodetic observations are sensitive to spatial slip features smaller than 64 km. In distinction, the synthesized seafloor deformation of all models exhibits poor correlation, indicating sensitivity to small-scale slip features. Our findings suggest that fine-scale slip features cannot be unambiguously resolved by remote or sparse observations, such as the three data types tested in this study. However, better resolution may become achievable from uniformly gridded dense offshore instrumentation.

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Impulsive Tsunami and Large Runup Along the Sanriku Coast of Japan Produced by an Inelastic Wedge Deformation Model

Cited by 10 publications

References 44 publications

Complex tsunamigenic near-trench seafloor deformation during the 2011 Tohoku–Oki earthquake

Complex tsunamigenic near-trench seafloor deformation during the 2011 Tohoku–Oki earthquake

Evaluating the Tsunamigenic Potential of Buried Versus Trench‐Breaching Megathrust Slip

A quantitative comparison and validation of finite-fault models: The 2011 Tohoku-Oki earthquake

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