Lithospheric strength inferred from modeling of buckling structure: Implications for stress state of the East Sea (Japan Sea)

The East Sea (Sea of Japan) is a back–arc basin that underwent a complex deformation history associated with the relative motions of major tectonic plates. Constraining the crustal composition and rheology of the Ulleung Basin in the East Sea is essential for understanding back–arc basin dynamics. We perform finite element modeling using a wide range of rheologies (i.e., oceanic/continental crust and Moho temperature) to analyze small sedimentary buckling structures with wavelengths of ∼60–70 km and amplitudes of ∼150–200 m observed in the Ulleung Basin. When a high temperature (i.e., 570–640 °C) is adopted at Moho (depth of 12 km), both models with oceanic and continental crusts show surface topographies similar to the buckled morphology observed in the region. Furthermore, our new finding based on the numerical modeling constrains the stress of the lithosphere beneath the western margin of the East Sea. The depth–integrated stresses of the models that produce the buckling structures are <1.5 TN/m, which is much lower than those observed at plate boundaries. Thus, we argue that the Ulleung Basin does not fully sustain far–field tectonic stress propagation from its major trenches into the Korean Peninsula. The findings of this study suggest a need for further exploration of internal factors that may influence intraplate faults in SE Korea.