Fault “Corrosion” by Fluid Injection: A Potential Cause of the November 2017 5.5 Korean Earthquake

Figure 11

Conceptual model linking injection into well PX-1 to the 15 November 2017 earthquake. Panels depict NW-SE cross-sections across the Namsong Fault (cf. Figure 2(b)), not to scale. The “zig-zag” pattern of fracturing reflects the analysis indicating a preferred orientation, given the local stress field, at 30° dip towards S69°E or N69°W, or towards N83°E or S83°W, depending on the choice of model stress field. Using standard theory, the largest earthquake in August 2017 ( 1.9; [17]) would correspond to shearing of a fracture with dimensions no greater than ~50 m, indicating the probable upper bound to the individual “zig-zag” fracture segments. See text for discussion.

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