Joint Inversion of Rayleigh-Wave Phase/Group Velocities Using a 3D Reference Model for Crustal Velocity Structure of Gangwon Province in the Korean Peninsula

Gangwon Province exhibits strong topographic relief and significant variations in Moho depth, necessitating the use of a 3D reference model for reliable crustal velocity imaging. To construct this model, we incorporated ETOPO1 topography, Moho depth estimates from receiver functions, and near-surface sedimentary layers constrained by P-wave polarization angle inversion essential for improved fitting of short-period dispersion curves. Rayleigh-wave phase and group velocities were measured from ambient-noise cross-correlation functions using data from 101 broadband seismometers and accelerometers for periods of 1–16 s. To extend sensitivity to deeper structures, we also included longer-period (10–40 s) Rayleigh-wave phase velocities derived from regional Helmholtz tomography. These three complementary datasets were jointly inverted to produce a high-resolution 3D S-wave crustal velocity model of Gangwon Province. The resulting model reveals pronounced low-velocity anomalies bounded by the Inje and Geumwang faults, suggesting the presence of compositional heterogeneity and mechanically weak zones. These results provide quantitative 3D constraints on major fault systems and crust–uppermost mantle structure in Gangwon Province.