Static Slip Model of the 2017 Mw 5.4 Pohang, South Korea, Earthquake Constrained by the InSAR Data

An M-w 5.4 earthquake occurred in the city of Pohang in the southeastern part of the Korean Peninsula on 15 November 2017. It was a moderate-sized crustal event but triggered enormous attention from the Korean public because strong shaking was felt over the whole country, and it had been just a year since the M-w 5.5 Gyeongju earthquake, the largest instrumentally recorded event in the country. Both earthquakes occurred within 40 km of each other. The Pohang earthquake provides a unique opportunity to constrain the static slip model of an earthquake in Korea using spaceborne Interferometric Synthetic Aperture Radar (InSAR) observations because the focal depth is relatively shallow (similar to 4 km), and surface displacement fields were successfully obtained by both descending and ascending orbits of the Sentinel-1A/B satellites. We performed a linear slip inversion using the InSAR data. Our slip model reveals that a major slip associated with the event occurred in the northeastern part of the hypocenter rather than in the southwestern part. In addition, its rupture dimension and mean slip are 5 km (width) by 6 km (length) and 15 cm, respectively. The InSAR data also show that no significant postseismic deformation occurred after the event.