Failure of engineering structures and associated geotechnical problems during the 2022 M _L 6.8 Chihshang earthquake, Taiwan

On September 18, 2022, an earthquake with a local magnitude (M _L) 6.8 struck the southern part of Longitudinal Valley in southeastern Taiwan, resulting in the collapse and damage of many engineering structures. A field reconnaissance was conducted at the selected sites that experienced building and bridge damages and is presented in this paper. The focus is on geotechnical problems such as strong ground motion, ground rupture, soil liquefaction, and their influence on engineering structures. Strong motions of up to 0.6 g were induced, with similar intensity in the vertical and horizontal components near the epicenter. Widespread ground rupture traces were observed along the officially recognized active faults, inducing offsets up to tens of centimeters. Soil liquefaction was also noticed in this region, mainly on the river flood plain and characterized as gravel layer. The possible influence of these observed geotechnical characteristics on the damage pattern or failure mode of buildings, bridges, embankments, and levees was discussed and interpreted insightfully. The perspectives presented in this paper may serve as a reference to disaster prevention and mitigation in future events.