Effects of 1D and 3D Reference Velocity Models on Joint Inversion of Rayleigh-Wave Dispersion Curves in Gangwon Province, South Korea; [강원권 레일리파 분산곡선 연합역산 과정에서의 1차원 및 3차원 기준속도모델의 영향]

초록

Located in the eastern Korean Peninsula, Gangwon Province is characterized by abrupt changes in topography and Moho depth, indicating the need for a three-dimensional (3D) reference velocity model for reliable imaging of crustal and uppermost mantle velocity structure. To construct the 3D reference velocity model, we integrated ETOPO1 topography, a 3D sedimentary layer model and a 1D crustal velocity model constrained by average Rayleigh-wave phase- and group-velocity dispersion curves, and 3D Moho depth estimates derived from receiver functions. Rayleigh-wave phase and group velocities were measured from ambient-noise cross-correlation functions using one year of continuous waveform data recorded at 32 broadband seismic stations, yielding dispersion measurements over periods of 1-16 s. These datasets were jointly inverted using the 3D reference velocity model to obtain a 3D S-wave crustal velocity model beneath Gangwon Province. Comparison of inversion results obtained using 1D and 3D reference velocity models demonstrates that shallow velocity anomalies are more clearly resolved when the 3D reference velocity model is employed. At ~2 km depth, a -5% velocity anomaly (S-wave velocity of ~3.3 km/s) is observed beneath the Taebaeksan Basin, consistent with a sedimentary basin extending to ~1.7 km depth. The lowest velocities in the study area (-10%: ~3.0-3.3 km/s) occur along the east coast and are attributed to a thick sedimentary layer reaching ~600 m in thickness incorporated in the 3D reference velocity model. In addition, a -5% velocity anomaly extends to 8-10 km depth along major fault systems, possibly indicating fault-related crustal heterogeneity. These results suggest that incorporating realistic 3D crustal structure into the reference velocity model improves the fit to the observed data and enables more effective imaging of shallow crustal heterogeneity. © 2026 The KSEEG. Printed by Hanrimwon Publishing Company. All rights reserved.

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