Land Damage Mapping and Liquefaction Potential Analysis of Soils from the Epicentral Region of 2017 Pohang Mw 5.4 Earthquake, South Korea

Studies on earthquake-induced liquefaction and identification of source unit for causing liquefaction have been a major concern in sustainable land use development especially in low to moderate seismic areas. During the 2017 M w 5.4 Pohang earthquake, widespread liquefaction was reported around the Heunghae basin, which was the first ever reported case of liquefaction in the modern seismic history of Korea. The epicentral area is one of the major industrial hubs along the SE Korean Peninsula with no detailed liquefaction hazard map. The purpose of this study was to determine the land damage classification on the basis of surface manifestation of liquefaction features and carry out detailed liquefaction potential analysis to delineate the depth of liquefiable soil. This will eventually support developing a liquefaction hazard zonation map and sustainable development of infrastructure to minimize earthquake damages. In this present study, the southern part of the Heunghae basin, which has more field evidences of liquefaction than the northern part, was taken for detailed liquefaction analysis. From the detailed analysis, it was observed that the soils from 1.5 to 15 m depth with the probability of liquefaction varying from 2 to 20 are prone to liquefaction. On the basis of land damage pattern, the epicentral area falls in orange to red zone, which means the necessity of further detailed liquefaction analysis. This study urges more detailed liquefaction zonation should be carried out for the epicentral area and liquefaction hazard should be included in the multi-hazard map in the future for the sustainable land use planning.