Research ArticleGEOPHYSICS

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

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Science Advances  19 Jul 2017:
Vol. 3, no. 7, e1700113
DOI: 10.1126/sciadv.1700113
  • Fig. 1 Observed postseismic DRs after the Tohoku earthquake through the repeated GPS-A observations.

    Black and green vectors show the DRs with 1σ error ellipses relative to the North American plate estimated by this study and by the Japan Coast Guard (8), respectively. The observation periods are from September 2012 to May 2016 for black vectors and from September 2012 to January 2014 for green vectors. Gray vectors in the onshore region show the DRs relative to the North American (NA) plate from September 2012 to November 2015 at the GNSS Earth Observation Network (GEONET) sites. Yellow and red contours represent 20- and 50-m contours of the coseismic slip distribution (40), indicating the PRA and very large slip area (VLSA), respectively.

  • Fig. 2 Comparison of the observed DRs and the estimates by the VR model and FL.

    (A) Black vectors are the same as those in Fig. 1. Blue, red, and green vectors show VR-DRs, the modified VR-DRs, and VR-DRs with contributions of FL assuming full-locking conditions, respectively. (B) DRs of 14 sites [shown as gray squares in (A)] close to the trench projected on line AA′ [shown in (A)] to investigate the spatial characteristics near the trench. Horizontal axis indicates the trench-normal component (113°N) of the DRs. Vertical axis indicates the distance in kilometers along the line AA′ shown in (A). The observed DRs in the trench-normal component are represented as black squares with 1σ errors. Colored curves are smoothed cubic spline fitting of the modeled DRs: VR-DRs (blue), the modified VR-DRs (red dashed), and VR-DRs with contributions of FL (green dashed). Horizontal orange lines show northern and southern limits of the PRA.

  • Fig. 3 Comparison of the observed postseismic DRs with postseismic slip estimated by previous studies.

    Black and green vectors and yellow and red contours are the same as those in Fig. 1. Black rectangle shows the fault zone of the 1896 Meiji-Sanriku earthquake (Eq.) (18). Blue contours show the AS distribution (12). The cumulative postseismic slip for the 23 April 2011 to 10 December 2011 period derived by small repeating earthquakes (17) is shown as colored patches. Gray patches indicate no aseismic slip during the period. Black curve denotes the northeastern limit of the Philippine Sea plate (42).

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/3/7/e1700113/DC1

    fig. S1. GPS-A observation site distribution.

    fig. S2. Additional coseismic slip patches for VR calculation and postseismic DRs calculated by the layered VR structure model.

    fig. S3. Comparison of the observed DRs and VR-DRs with local FL in Segment-1.

    fig. S4. Comparison of the observed DRs and VR-DRs with local FL in PRA.

    fig. S5. Time series of the postseismic horizontal displacements at GPS-A observation sites.

    fig. S6. Fault patches for calculating the FL effects assuming full-locking conditions.

    table S1. Estimated array positions at GPS-A observation sites.

    table S2. Coseismic steps caused by the aftershocks on 7 December 2012.

    table S3. Estimated postseismic DRs relative to the North American plate.

  • Supplementary Materials

    This PDF file includes:

    • fig. S1. GPS-A observation site distribution.
    • fig. S2. Additional coseismic slip patches for VR calculation and postseismic DRs calculated by the layered VR structure model.
    • fig. S3. Comparison of the observed DRs and VR-DRs with local FL in Segment-1.
    • fig. S4. Comparison of the observed DRs and VR-DRs with local FL in PRA.
    • fig. S5. Time series of the postseismic horizontal displacements at GPS-A observation sites.
    • fig. S6. Fault patches for calculating the FL effects assuming full-locking conditions.
    • table S1. Estimated array positions at GPS-A observation sites.
    • table S2. Coseismic steps caused by the aftershocks on 7 December 2012.
    • table S3. Estimated postseismic DRs relative to the North American plate.

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