Along-trench variation in seafloor displacements after the 2011 Tohoku earthquake

Tomita, Fumiaki; Kido, Motoyuki; Ohta, Yusaku; Iinuma, Toshitaka; Hino, Ryota

doi:10.1126/sciadv.1700113

Cited by 87 publications

(113 citation statements)

References 40 publications

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“…Upper and lower panels of each sites show eastward and northward displacement, respectively. Red and black colors indicate the results of this study and those of Tomita et al (), respectively. Error bars of this study (red) show 10‐times estimation errors.…”

Section: Resultsmentioning

confidence: 58%

“…By contrast, all available data of both moving and fixed‐point surveys were employed in this study to determine the array geometry and array displacements by using a revised analysis scheme known as multiple campaign analysis (Honsho & Kido, ). As a result, the total amount of travel time data was revised to ~1.5 times that reported by Tomita et al (), and the accuracy of the array geometry was greatly improved.…”

Section: Observation and Data Collectionmentioning

confidence: 99%

“…Reference vertical profiles of the sound speed, which are referred to as v 0 ( z ) in the following section, were obtained from oceanographic observation data collected during the individual campaigns. This is another difference from Tomita et al (), in which a sound speed profile was prepared for each site based on an open climatological database, World Ocean Atlas 2013 (Locarnini et al, ; Zweng et al, ) and was used commonly for all campaigns at the site. Small differences in the reference profiles generally have no effect on the results of the array positioning as long as the Scripps Institution of Oceanography approach is adopted.…”

Section: Observation and Data Collectionmentioning

confidence: 99%

“…In addition, we explain the relationship between our approach and the previous methods in the formulation of gradient effects and the application to actual data. By applying the proposed method and using an improved analysis scheme to make full use of existing data (Honsho & Kido, ), we reevaluate the offshore postseismic deformation following the 2011 Tohoku earthquake by revising and updating our previous results of horizontal movement (Tomita et al, ). Finally, we discuss the implications of our results on viscoelastic relaxation, coseismic slip, and afterslip associated with the Tohoku earthquake.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Offshore Postseismic Deformation of the 2011 Tohoku Earthquake Revisited: Application of an Improved GPS‐Acoustic Positioning Method Considering Horizontal Gradient of Sound Speed Structure

et al. 2019

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One of the important issues on the GPS‐acoustic (GPS‐A) observation for sea bottom positioning is how to address the horizontal heterogeneity of the sound speed in oceans. This study presents an analysis method of GPS‐A data in the presence of a sloping sound speed structure. By applying this method and revising the analysis scheme to make full use of existing data, we reevaluated the horizontal postseismic deformations occurring ~1.5–5 years after the 2011 Tohoku earthquake. The revised horizontal movements have more uniform directions and rates between neighboring sites, suggesting enhancement of the array positioning accuracy. The revised displacement rate of the site on the incoming Pacific plate, located ~100 km northeast of the main rupture zone, was decreased significantly; it was only slightly, by 1.4 cm/year larger than the global motion of the Pacific plate, suggesting a relatively small effect of viscoelastic relaxation. The horizontal movements of the near‐trench sites above the main rupture zone were generally landward and were significantly faster than the Pacific plate motion, indicating a viscoelastic relaxation of 5–10 cm/year. The distribution of the fast landward movements peaked near 38°N at an updip of the mainshock hypocenter and extended significantly farther to the north than to the south. This implies the existence of a secondary coseismic slip patch in the northern area in addition to a primary slip patch at ~38°N. The occurrence of episodic slow slip in early 2015 to the north of the main rupture zone was also verified from the GPS‐A analyses.

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Section: Resultsmentioning

confidence: 58%

Section: Observation and Data Collectionmentioning

confidence: 99%

Section: Observation and Data Collectionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Offshore Postseismic Deformation of the 2011 Tohoku Earthquake Revisited: Application of an Improved GPS‐Acoustic Positioning Method Considering Horizontal Gradient of Sound Speed Structure

et al. 2019

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“…Offshore geodetic data are admittedly challenging to obtain, despite recent progress (Maksymowicz et al, 2017;Tomita et al, 2017;Wallace et al, 2016;Yokota et al, 2016), but these measurements may be most effective to constrain the rheology of the subducting slab and fault processes near the trench. Flow in the oceanic asthenosphere creates landward surface displacements above the coseismic rupture and seaward displacements away from it.…”

Section: Discussionmentioning

confidence: 99%

Asthenosphere Flow Modulated by Megathrust Earthquake Cycles

Barbot

2018

Geophysical Research Letters

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Subduction megathrusts develop the largest earthquakes, often close to large population centers. Understanding the dynamics of deformation at subduction zones is therefore important to better assess seismic hazards. Here I develop consistent earthquake cycle simulations that incorporate localized and distributed deformation based on laboratory‐derived constitutive laws by combining boundary and volume elements to represent the mechanical coupling between megathrust slip and solid‐state flow in the oceanic asthenosphere and in the mantle wedge. The model is simplified, in two dimensions, but may help the interpretation of geodetic data. Megathrust earthquakes and slow‐slip events modulate the strain rate in the upper mantle, leading to large variations of effective viscosity in space and time and a complex pattern of surface deformation. While fault slip and flow in the mantle wedge generate surface displacements in the same, that is, seaward, direction, the viscoelastic relaxation in the oceanic asthenosphere generates transient surface deformation in the opposite, that is, landward, direction above the rupture area of the mainshock. Aseismic deformation above the seismogenic zone may be challenging to record, but it may reveal important constraints about the rheology of the subducting plate.

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Seafloor Displacement After the 2011 Tohoku‐oki Earthquake in the Northern Japan Trench Examined by Repeated Bathymetric Surveys

Fujiwara

Ferreira

Bachmann

et al. 2017

Geophysical Research Letters

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We conducted multibeam bathymetric surveys crossing the northern Japan Trench offshore Sanriku and examined seafloor displacement by means of the difference in bathymetry before and after the 11 March 2011 Tohoku‐oki earthquake. The seafloor displacements were less than several meters in vertical displacement and less than 20 m in trench‐normal horizontal displacement; consequently, lower amplitude seafloor displacements were evaluated. Comparatively, the landward lower slope near the trench was uplifted, the middle slope was subsided, and the midslope terrace was depressed after the earthquake. Therefore, localized very large fault slip or very large submarine landslide is unlikely. Instead, smaller uplift of the lower slope near the trench extending broader along the trench seems to be plausible explanation for the devastating tsunami source in the northern Japan Trench area.

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Along-trench variation in seafloor displacements after the 2011 Tohoku earthquake

Abstract: Seafloor displacements observed after the Tohoku earthquake place large constraints on assessing the deformation process.

Cited by 87 publications

References 40 publications

Offshore Postseismic Deformation of the 2011 Tohoku Earthquake Revisited: Application of an Improved GPS‐Acoustic Positioning Method Considering Horizontal Gradient of Sound Speed Structure

Offshore Postseismic Deformation of the 2011 Tohoku Earthquake Revisited: Application of an Improved GPS‐Acoustic Positioning Method Considering Horizontal Gradient of Sound Speed Structure

Asthenosphere Flow Modulated by Megathrust Earthquake Cycles

Seafloor Displacement After the 2011 Tohoku‐oki Earthquake in the Northern Japan Trench Examined by Repeated Bathymetric Surveys

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