Research ArticleSeismology

Cascading elastic perturbation in Japan due to the 2012 Mw 8.6 Indian Ocean earthquake

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Science Advances  16 Oct 2015:
Vol. 1, no. 9, e1500468
DOI: 10.1126/sciadv.1500468
  • Fig. 1 Maps.

    (A and B) These maps show (A) the IOE and (B) our study area in Japan. Symbols in (B) are as follows: blue and green triangles are Hi-net stations used to calculate seismic velocities; green stations are used to calculate seismic coherence. Red circles are the epicenters of the 2011 TOE and shallow earthquakes discussed in the text. Black triangles are F-net station HRO and extensometer KTA. Inset shows location of shallow earthquakes; hatch marks indicate region where seismic velocities are calculated.

  • Fig. 2 Observations.

    (A) Earthquakes (origin 31.32°N, 134.10°E). Red triangles represent P1 and P2 (top to bottom). Blue triangle represents P0. Black vertical line extending through all subfigures is IOE. (B) Stacked interstation seismic coherence. (C) Cumulative aftershocks for P0 and P2 (black stars) with map view inset. Blue and red curves are cumulative number of earthquakes in the P0 and P2 clusters, respectively. The P0 main shock and northern aftershocks (blue dots) generally precede the P2 main shock and aftershocks (red dots), and the P0 southern aftershocks (red dots). Vertical dashed lines mark P0 (blue, left) and P2 (red), and initiation time of earthquake cluster following P0 (blue, right). (D) Stacked fractional change in interstation travel times with 1 SD; red shaded area indicates time period where travel time decrease may have initiated. (E) Volumetric strain at extensometer KTA.

  • Fig. 3 Geodetic.

    (A) Two sets of GPS stations (blue and green). The mean position of the blue stations is subtracted from mean position of the green stations along the direction of plate convergence indicated by the black arrow. (B) Times series of the difference. The red line indicates the IOE. The two sets of stations are rapidly diverging after the TOE, but long period strain rate is near zero at the time of the IOE and slightly negative by the end of 2012. During 2012, the strain alternates between contraction and dilation.

  • Fig. 4 Interpretation.

    (A to C) Cycle of stress transfer from (A) plate interface to shallow fore arc (B) resulting in normal faulting earthquakes and (C) stress transfer to interior Honshu Island. Blue triangles represent Hi-net stations. Red stars are normal faulting earthquakes.

  • Table 1 Hypocenter information for earthquakes P0, P1, and P2 (Fig. 1).

    JMA, Japan Meteorological Agency; NEIC, National Earthquake Information Center; UTC, Coordinated Universal Time; AQUA, Japan Focal Mechanism Catalog System.

    depth (km)
    36.829141.3435.6 (5.4)28.8 (5.0)
    37.452141.7345.9 (5.5)26.8 (13)
    36.947141.4226.0 (5.7)31.5 (8.0)

Supplementary Materials

  • Supplementary Materials

    This PDF file includes:

    • Fig. S1. Migration of seismic coherence.
    • Legends for movies S1 and S2

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    Other Supplementary Material for this manuscript includes the following:

    • Movie S1 (.mov format). High sample rate seismic coherence.
    • Movie S2 (.mov format). Low sample rate seismic coherence.

    Files in this Data Supplement:

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