Abstract
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 Mw 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.
Highlights
During earthquake shaking or other rapid loadings, mostly saturated sandy/silty soil loses its strength and stiffness and behaves as a liquid which is known as liquefaction [1,2,3]
A cross-section covering 10 km along the E-W direction of the Heunghae basin was selected on the basis of surface manifestation of sand boils during the Pohang earthquake
Since there were no borehole data available passing thought the center of the basin, the southern part of the basin was taken for the detailed liquefaction analysis as a representative section of the basin
Summary
During earthquake shaking or other rapid loadings, mostly saturated sandy/silty soil loses its strength and stiffness and behaves as a liquid which is known as liquefaction [1,2,3]. The basic understanding of the relationship between cyclic loading during an earthquake and soil liquefaction has been largely derived from laboratory studies, such as cyclic triaxial tests, shake table tests, resonant column tests, centrifuge modeling, etc. Despite decades of research towards understanding the liquefaction hazard and its mitigation criteria, the recent large magnitude earthquakes like the 2016 Kumamoto earthquake (Mw 7.0) and 2018 Sulawesi earthquake ((Mw 7.5) and moderate magnitude earthquakes like 2009 Olancha earthquake in the United States (Mw 5.2), 2017 Pohang earthquake in South Korea (Mw 5.5) indicate that, there is still ambiguity on reducing the liquefaction hazard during moderate to large magnitude earthquakes [24,25,26]
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