Lithospheric flexure and effective elastic thickness under the Ulleung Basin in the East Sea using gravitational coherence

Abstract

To estimate a non-uniform effective elastic thickness ($T_e$) of lithosphere across Korean Peninsula and the Surrounding Seas (KPSS), we employ gravitational coherence analysis between gravity anomalies and topography/bathymetry data in the Fourier domain. Exploring crustal flexure and effective elastic thickness variations can offer insights into flexural strength, and evolutionary mechanics of the lithosphere under Ulleung Basin (UB). Our approach involves two scenarios: a large study area spanning the KPSS, and a more targeted investigation focused on UB. Dividing the study area into overlapping windows enables us to recover non-uniform $T_e$ values over the targeted regions. The UB study area is divide to 200 km by 200 km windows, and KPSS is divided to 400 km, 600 km, and 800 km windows to recover both short wavelengths and long wavelengths of $T_e$. Our results reveal a $T_e$ range of 843 km for KPSS and recovered $T_e$ range from 1 to 10 km for UB. The estimated elastic thickness values in southern part of this basin are smaller compared to central and northern parts. These findings are consistent with prior estimations and comparative studies within the region, improving the understanding of UB's lithospheric properties. The recovered $T_e$ values for UB ($T_e<6\mathrm{km}$) suggests a young and weak oceanic lithosphere under this region. The alignment between recovered $T_e$ configuration and tectonic features in KPSS displays a large-scale lithospheric structure.