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

Figure 1

Location map for the city of Pohang in the SE part of the Korean peninsula (upper inset showing wider location, lower inset showing greater local detail), showing Late Cenozoic right-lateral faults (from [96]), the Namsong Fault (from [7]), and the epicentres of the 12 September 2016 and 15 November 2017 earthquakes (from [7, 46]). The right-lateral faults depicted follow prominent fault-line escarpments that dominate the local topography, being readily visible on topographic maps and satellite imagery (such as Figure 1 of [96]). The local inset shows the Namsong Fault (depicted schematically at the updip limit of coseismic reactivation in 2017, from [6]), the Heunghae alluvial plain (pale shading), the EGS project site (G), Namsong village (N), and the Pohang thermal spa resort that yielded hydrochemical data (T; coordinates from [97]).