Crustal deformation of SE Korea caused by back-arc opening of the East Sea (Sea of Japan) commenced locally in the Late Oligocene. Intense deformation occurred during the Early Miocene, accompanying extension of parallelogram-shaped pull-apart basins between NNW-striking principal displacement zones, clockwise rotation and northwestward tilting of blocks, and southwestward propagating rifting. At about 17 Ma, the crustal deformation suddenly expanded westward and northward owing to activation of the Yeonil Tectonic Line, resulting in a dramatic change of depositional environment and the subsidence of wedge-shaped pull-apart basins. The Yeonil Tectonic Line and western border faults of the Pohang Basin are the westernmost limit of the Miocene crustal deformation. All the features of crustal deformation in SE Korea support the pull-apart model for the East Sea opening. However, they indicate that the NNW-striking faults such as the Yeonil Tectonic Line acted as the principal displacement zones rather than the NNE-striking Yangsan Fault under a consistent dextral simple shear. At about 16 Ma, the collision of the Philippine Sea Plate with the Japanese Islands caused a tectonic inversion. This inversion resulted in a compositional change of basaltic magma at about 15 Ma and crustal uplift in SE Korea, which caused the cessation of sedimentation at about 10 Ma.

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Offshore installations are exposed to hydrocarbon explosion and/or fire accidents. Especially, explosions lead serious damages to human, safety and environment. To minimize and prevent the damage from explosions, blast walls are generally installed in oil and gas production structures. Typical blast walls are divided into flat, corrugated, and stiffened type of blast walls. Among of them, corrugated blast walls are frequently used for reasons such as construction, cost, and energy absorption etc.However, it has been known that corrugated type of blast wall buckles between web and flange under the explosion loads, and it loses its stiffness. It means that the buckling phenomenon of blast wall is closely related to the structural strength. This study focuses on the structural characteristics of blast wall under quasi-static and dynamic (explosion) loads according to with or without flat-plated stiffener. Finally, it could be concluded that flat type of stiffener is located at the buckling region to delay the buckling and improve the strength of blast walls. KeywordsOffshore installations, corrugated blast wall, buckling, stiffened blast wall, nonlinear finite element analysis

In order to characterize the Neotectonic crustal deformation and current stress field in and around the Korean Peninsula and to interpret their tectonic implications, this paper synthetically analyzes the previous Quaternary fault and focal mechanism solution data and recent geotechnical in-situ stress data and examines the characteristics of crustal deformations and tectonic settings in and around East Asia after the Miocene. Most of the Quaternary fault outcrops in SE Korea occur along major inherited fault zones and show a NS-striking top-to-the-west thrust geometry, indicating that the faults were produced by local reactivation of appropriately oriented preexisting weaknesses under EW-trending pure compressional stress field. The focal mechanism solutions in and around the Korean Peninsula disclose that strike-slip faulting containing some reverse-slip component and reverse-slip faulting are significantly dominant on land and in sea area, respectively. The P-axes are horizontally clustered in ENE-WSW direction, whereas the T-axes are girdle-distributed in NNW direction. The geotechnical in-situ stress data in South Korea also indicate