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

Figure 5

Four determinations of the focal mechanism of the Pohang mainshock. Diagrams are displayed as standard equal area projections of the lower focal hemisphere, with north at the top and compressional quadrants of the double-couple P-wave radiation pattern shaded. , , and denote the -axis, -axis, and null axis, respectively; denotes the slip vector, and denotes the direction perpendicular to the fault plane. (a) Determined by the U.S. Geological Survey [95]; (b) determined by Kim et al. [7]; (c) determined by Grigoli et al. [6]; (d) determined by Lee et al. [5].

(a)

(b)

(c)

(d)