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Assessing whether the 2017 Mw 5.4 Pohang earthquake in South Korea was an induced event

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Science  01 Jun 2018:
Vol. 360, Issue 6392, pp. 1007-1009
DOI: 10.1126/science.aat6081
  • Fig. 1 Tectonic map of northeast Asia.

    Saw-toothed lines with solid teeth denote subduction zones. The broken line with open teeth represents an incipient subduction zone (30). EU, Eurasian Plate; NA, North American Plate; PS, Philippine Sea Plate; PA, Pacific Plate.

  • Fig. 2 Geologic map and column of the Pohang basin.

    (A) Map showing rocks and faults of the Pohang basin and adjacent area. One permanent seismic station operated by the Korea Meteorological Administration (PHA2) and our eight temporary seismic stations are represented by a dark blue square and green triangles, respectively. The green square denotes the site of the Pohang enhanced geothermal system (EGS). The geologic map was compiled from (18, 19). (B) Geologic column of the Pohang EGS site with injection well. The geologic column was compiled from (19, 20).

  • Fig. 3 Spatial distribution of epicenters and hypocenters of the 2017 Pohang earthquake sequence.

    (A) Epicenters of six foreshocks (red circles), mainshock (red star), and 210 aftershocks (black open circles) recorded in the first 3 hours after the mainshock. The location of the Pohang EGS is indicated by a green square. Blue triangles represent our eight temporary seismic stations. The red beach ball represents the source mechanism of the mainshock. Black beach balls show the focal mechanism solutions of representative aftershocks. Numbers above beach balls are local magnitudes. The black beach balls of the ML 2.4 and 3.5 aftershocks, recorded 1 and 3 days after the mainshock, respectively, show strike-slip faulting. X−X′ and Y−Y′ denote the locations of the cross sections shown in (B) and (C), respectively. (B and C) Hypocentral distributions of earthquakes, projected onto vertical planes along the lines X−X′ (B) and Y−Y′ (C) shown in (A). The red beach ball in (B) represents the focal mechanism of the mainshock projected onto a vertical cross section. PX1 and PX2 denote production and injection wells, respectively. Other symbols are the same as for (A).

  • Fig. 4 History of fluid injection volume.

    Volume of injected and bleed-off fluid (left axis) and net fluid volume (right axis) as a function of time. Red circles denote times of seismic events from data provided by the MTIE (63 events; magnitude information is only available for M > 1). Dark blue circles denote seismic events determined by matched-filter analysis (148 events). The right axis also gives the local magnitudes of seismic events.

Supplementary Materials

  • Assessing whether the 2017 Mw 5.4 Pohang earthquake in South Korea was an induced event

    Kwang-Hee Kim, Jin-Han Ree, YoungHee Kim, Sungshil Kim, Su Young Kang, Wooseok Seo

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

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    • Materials and Methods
    • Figs. S1 to S5
    • References
    Correction (31 May 2018): Numbers on the "east" axis of fig. S3 were corrected. Panels A to E in fig. S5 were changed from color to black and white per (27); in addition, panel F (color version of panel B) was added, along with the reference from which it was derived (38).
    The original version is accessible here.

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