Analysis of Crustal Velocity Structure Beneath Gangwon Province, South Korea, Using Joint Inversion of Receiver Functions and Surface Wave Dispersion

초록

To analyze the crustal velocity structures beneath 21 broadband seismic stations in Gangwon Province, South Korea, we first applied the H-kappa stacking method to 139 teleseismic event data (Mw >= 5.8 and the epicentral distance of 30 degrees - 90 degrees) occurring between March 18, 2019 and December 31, 2022 to estimate the Moho depths and V-p/V-s ratios beneath each station. The Moho depths and V p/V s ratios from the H-. stacking method range from 24.9 to 33.2 km depth and 1.695 - 1.760, respectively, and the estimated V-p/V-s ratios were applied to the joint inversion of receiver functions and surface wave dispersion to obtain 1-D crustal velocity models beneath each station. The resulting Moho depths range from 25.9 to 33.7 km depth, similar to the results from the H-kappa stacking method. Moho depth results from the both methods are generally consistent with Airy's isostasy. The 1-D crustal velocity models confirm that the existence of 2 km thick low-velocity layers with P-wave velocities of 5 km/s or less at some stations in the Taebaeksan basin, and at the stations CHNB and GAPB in northern Gangwon Province, which are located above the Cenozoic sedimentary layer. The station SH2B, although not overlying a sedimentary layer, has a low P-wave velocity near the surface, which is probably due to various factors such as weathering of the bedrock. We also observe a velocity inversion with decreasing velocity with depth at all stations within 4 - 12 km depths, and mid-crustal discontinuities possibly due to density differences in the rocks at around 10 km depth below some stations.

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