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The November 2017 Mw 5.5 Pohang earthquake: A possible case of induced seismicity in South Korea

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Science  01 Jun 2018:
Vol. 360, Issue 6392, pp. 1003-1006
DOI: 10.1126/science.aat2010
  • Fig. 1 The 2016 and 2017 Mw 5.5 earthquakes in South Korea.

    (A) Regional map showing locations of the Gyeongju and Pohang earthquakes, the Yangsan fault, and the available open seismic stations. (B) Map of the study area showing the main faults of the area, the distribution of seismicity with respect to the EGS site, and the mechanisms of the largest events. A more detailed map of the area of study (outlined by the yellow square) is shown in Fig. 2A. UTC, universal time coordinated.

    EGS SITE PHOTO: COURTESY OF THE DESTRESS PROJECT TEAM
  • Fig. 2 Spatial distribution of the 2017 Pohang seismic sequence.

    (A) Detailed map showing the epicentral distribution of seismicity and (B) two cross sections displaying the depth distribution of seismicity (including location uncertainties) and the fault as inferred by geodetic analysis. The EGS site is located at 36°06′23.34′′N, 129°22′46.08′′E and includes the two injection wells that reach depths of 4127 and 4348 m (3). (C) Focal depth distribution of earthquakes in the study region and comparison with the 2016 Gyeongju seismic sequence.

  • Fig. 3 DInSAR data and model.

    (A) Surface deformation (satellite line-of-sight displacements) obtained with InSAR. Seismicity and the extrapolated fault trace are indicated by black circles and a dashed line, respectively. (B) Modeled surface deformation using a rectangular fault plane with the following parameters: latitude = 36.100° ± 0.005°, longitude = 129.383° ± 0.003° (center of the rectangular fault), depth = 4.3 ± 0.3 km (upper edge of the fault), strike (from north) = 225° ± 12°, dip (from horizon) = 75° ± 11°, length = 5.0 ± 0.7 km, width = 1.6 ± 0.4 km, slip = 1 ± 0.22 m, and rake = 123° ± 35°. (C) Difference between InSAR data and model. The standard deviation is <0.5 cm, which is below the accuracy threshold of the measurements.

  • Fig. 4 Coulomb stress modeling.

    (A) Static coulomb failure stress showing the effect of the 2016 Gyeongju earthquake at 4 km of depth on the fault activated by the 2017 Pohang event and (B) the effect of this latter event on the Yangsan fault at 14 km of depth. Receiver faults are denoted by red dot-dashed lines. The triangle represents the local accelerometer, and the squares denote the injection wells.

Supplementary Materials

  • The November 2017 Mw 5.5 Pohang earthquake: A possible case of induced seismicity in South Korea

    F. Grigoli, S. Cesca, A. P. Rinaldi, A. Manconi, J. A. López-Comino, J. F. Clinton, R. Westaway, C. Cauzzi, T. Dahm, S. Wiemer

    Materials/Methods, Supplementary Text, Tables, Figures, and/or References

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    • Supplementary Text
    • Figs. S1 to S12
    • References

    Additional Data

    Waveform and Local Accelerometer Data

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