Potential tsunamigenic faults of the 2011 off the Pacific coast of Tohoku Earthquake (original) (raw)
Related papers
2016
obtained by inversions of seismic waves and geodetic observations are used to reconstruct deep-water tsunami recordings from DART buoys near Japan. One model is from least-squares inversion of teleseismic P waves, and another from iterative least-squares search-based joint inversion of teleseismic P waves, short-arc Rayleigh wave relative source time functions, and high-rate GPS observations from northern Honshu. These rupture model inversions impose similar kinematic constraints on the rupture growth, and both have concentrations of slip of up to 42 m up-dip from the hypocenter, with substantial slip extending to the trench. Tsunami surface elevations were computed using the model NEOWAVE, which includes a vertical momentum equation and a non-hydrostatic pressure term in the nonlinear shallow-water equations to account for the time-history of seafloor deformation and propagation of weakly dispersive tsunami waves. Kinematic seafloor deformations were computed using the Okada soluti...
Mechanism of the 2011 Tohoku-oki earthquake (Mw 9.0) and tsunami: Insight from seismic tomography
Journal of Asian Earth Sciences, 2013
To clarify the generating mechanism of the 2011 Tohoku-oki earthquake (Mw 9.0) and the induced tsunami, we determined high-resolution tomographic images of the Northeast Japan forearc. Significant lateral variations of seismic velocity are visible in the megathrust zone, and most large interplate thrust earthquakes are found to occur in high-velocity (high-V) areas. These high-V zones may represent high-strength asperities at the plate interface where the subducting Pacific plate and the overriding Okhotsk plate are coupled strongly. A shallow high-V zone with large coseismic slip near the Japan Trench may account for the mainshock asperity of the 2011 Tohoku-oki earthquake. Because it is an isolated asperity surrounded by low-velocity patches, most stress on it was released in a short time and the plate interface became decoupled after the Mw 9.0 earthquake. Thus the overriding Okhotsk plate there was shot out toward the Japan Trench and caused the huge tsunami.
Earth, Planets and Space, 2011
Finite-source rupture models for the great 11 March 2011 off the Pacific coast of Tohoku (M w 9.0) Earthquake obtained by inversions of seismic waves and geodetic observations are used to reconstruct deep-water tsunami recordings from DART buoys near Japan. One model is from least-squares inversion of teleseismic P waves, and another from iterative least-squares search-based joint inversion of teleseismic P waves, short-arc Rayleigh wave relative source time functions, and high-rate GPS observations from northern Honshu. These rupture model inversions impose similar kinematic constraints on the rupture growth, and both have concentrations of slip of up to 42 m up-dip from the hypocenter, with substantial slip extending to the trench. Tsunami surface elevations were computed using the model NEOWAVE, which includes a vertical momentum equation and a non-hydrostatic pressure term in the nonlinear shallow-water equations to account for the time-history of seafloor deformation and propagation of weakly dispersive tsunami waves. Kinematic seafloor deformations were computed using the Okada solutions for the rupture models. Good matches to the tsunami arrival times and waveforms are achieved for the DART recordings for models with slip extending all the way to the trench, whereas shifting fault slip toward the coast degrades the predictions.
Outer trench-slope faulting and the 2011 M w 9.0 off the Pacific coast of Tohoku Earthquake
Earth, Planets and Space, 2011
The 11 March 2011 off the Pacific coast of Tohoku Earthquake (M w 9.0) produced megathrust displacements of at least 40 m. The resulting tsunami devastated the Honshu coast southwest of regions struck by earthquakegenerated tsunami in 1611, 1896 and 1933. The 1896 Meiji-Sanriku earthquake was also an underthrusting earthquake, but the 1933 Sanriku-oki earthquake was a trench-slope normal faulting event; both generated inundation heights of 10 to 25 m along the coast of Iwate prefecture. Possible occurrence of a great outer trenchslope earthquake seaward of the 2011 Tohoku Earthquake along a southwestward extension of the 1933 fault zone is a concern. The second largest 2011 aftershock, an outer rise M w 7.7 normal faulting earthquake occurred near the southern end of the 1933 rupture. Additional aftershock activity has been distributed along a trend below the trench and diffusely spread in the outer rise, seaward of the megathrust region where the largest slip occurred. Coulomb stress perturbations of at least 5-10 bars are calculated for outer rise normal fault geometries for mainshock slip models. Whether a future great trench slope event will occur is uncertain, but the potential tsunamigenic hazard can be gauged by the huge inundations accompanying the 1933 rupture.
Clues from joint inversion of tsunami and geodetic data of the 2011 Tohoku-oki earthquake
2012
The 2011 Tohoku-oki (Mw 9.1) earthquake is so far the best-observed megathrust rupture, which allowed the collection of unprecedented offshore data. The joint inversion of tsunami waveforms (DART buoys, bottom pressure sensors, coastal wave gauges, and GPS-buoys) and static geodetic data (onshore GPS, seafloor displacements obtained by a GPS/acoustic combination technique), allows us to retrieve the slip distribution on a non-planar fault. We show that the inclusion of near-source data is necessary to image the details of slip pattern (maximum slip ,48 m, up to ,35 m close to the Japan trench), which generated the large and shallow seafloor coseismic deformations and the devastating inundation of the Japanese coast. We investigate the relation between the spatial distribution of previously inferred interseismic coupling and coseismic slip and we highlight the importance of seafloor geodetic measurements to constrain the interseismic coupling, which is one of the key-elements for long-term earthquake and tsunami hazard assessment.
Tsunami source of the 2011 off the Pacific coast of Tohoku Earthquake
Earth, Planets and Space, 2011
Tsunami waveform inversion for the 11 March, 2011, off the Pacific coast of Tohoku Earthquake (M 9.0) indicates that the source of the largest tsunami was located near the axis of the Japan trench. Ocean-bottom pressure, and GPS wave, gauges recorded two-step tsunami waveforms: a gradual increase of sea level (∼2 m) followed by an impulsive tsunami wave (3 to 5 m). The slip distribution estimated from 33 coastal tide gauges, offshore GPS wave gauges and bottom-pressure gauges show that the large slip, more than 40 m, was located along the trench axis. This offshore slip, similar but much larger than the 1896 Sanriku "tsunami earthquake," is responsible for the recorded large impulsive peak. Large slip on the plate interface at southern Sanriku-oki (∼30 m) and Miyagi-oki (∼17 m) around the epicenter, a similar location with larger slip than the previously proposed fault model of the 869 Jogan earthquake, is responsible for the initial water-level rise and, presumably, the large tsunami inundation in Sendai plain. The interplate slip is ∼10 m in Fukushima-oki, and less than 3 m in the Ibaraki-oki region. The total seismic moment is estimated as 3.8 × 10 22 N m (M w = 9.0).
Oceanography, 2014
Integrated Ocean Drilling Program (IODP) Expedition 343, named the Japan Trench Fast Drilling Project (JFAST), drilled ocean floor boreholes through the fault zone of the 2011 Tōhoku-Oki earthquake (M9.0) to enhance understanding of the rupture process and tsunami generation. This project investigated the very large fault slip that caused the devastating tsunami by making borehole stress measurements, sampling the plate boundary fault zone, and taking temperature measurements across the fault zone. The results show that the earthquake rupture occurred in a narrow fault zone (< 5 m). Based on both laboratory experiments on fault zone material and eScholarship provides open access, scholarly publishing services to the University of California and delivers a dynamic research platform to scholars worldwide.
Modeling of the 2011 Tohoku Near-Field Tsunami from Finite-Fault Inversion of Seismic Waves
Bulletin of the Seismological Society of America, 2013
The great 2011 Tohoku earthquake with M w 9.0 generated strong shaking and a destructive tsunami along the northeastern Japan coasts. We utilize a finite-fault model obtained from seismic P-wave inversion to characterize the timedependent fault displacements and seafloor motions. A nonhydrostatic long-wave model describes the resulting tsunami for investigation of the generation mechanism in terms of the rupture process and the ocean wave dynamics over the continental margin. The computed near-field tsunami, which evolves from two dominant wave components generated by seafloor uplift near the epicenter and trench, is consistent with the recorded water-level data around the source. Spectral analysis of the computed ocean surface elevation reveals energetic, standing edge waves with periods 32-115 min along the continental margin from Chiba to Hokkaido. While superposition of the two dominant wave components exacerbates the impact along the coasts fronting the rupture, constructive interference of standing edge waves accounts for the belated arrivals of the largest waves on the adjacent coasts and persistent wave activities in the aftermath.
Journal of Geophysical Research: Solid Earth, 2014
for the M w 9.0 Tohoku-Oki earthquake reconciling geodesy, seismology, and tsunami records, Abstract The 11 March 2011 M w 9.0 Tohoku-Oki earthquake was recorded by an exceptionally large amount of diverse data offering a unique opportunity to investigate the details of this major megathrust rupture. Many studies have taken advantage of the very dense Japanese onland strong motion, broadband, and continuous GPS networks in this sense. But resolution tests and the variability in the proposed solutions have highlighted the difficulty to uniquely resolve the slip distribution from these networks, relatively distant from the source region, and with limited azimuthal coverage. In this context, we present a finite fault slip joint inversion including an extended amount of complementary data (teleseismic, strong motion, high-rate GPS, static GPS, seafloor geodesy, and tsunami records) in an attempt to reconcile them into a single better resolved model. The inversion reveals a patchy slip distribution with large slip (up to 64 m) mostly located updip of the hypocenter and near the trench. We observe that most slip is imaged in a region where almost no earthquake was recorded before the main shock and around which intense interplate seismicity is observed afterward. At a smaller scale, the largest slip pattern is imaged just updip of an important normal fault coseismically activated. This normal fault has been shown to be the mark of very low dynamic friction allowing extremely large slip to propagate up to the free surface. The spatial relationship between this normal fault and our slip distribution strengthens its key role in the rupture process of the Tohoku-Oki earthquake.