Continent-Side Paleo-Rift Structure in the Western East Sea (Sea of Japan) and Linkage Between Moho Uplift and Mountain Range Formation

The continental-side paleo-rift structure in the east-central Korean Peninsula is investigated using joint inversion of receiver functions and surface-wave dispersions based on dense seismic networks. The joint inversion analysis provides precise constraints on crustal thickness and $V_P/V_S$ ratios, and high-resolution 3-D shear-wave velocity model. The model reveals distinct lateral and vertical variations associated with tectonic evolution during continental rifting. Inland regions exhibit typical continental crustal thickness ($\sim$33 km) and moderate $V_P/V_S$ ratios (1.60–1.75). On the other hand, coastal regions present shallower Moho depths ($\sim$24 km), high $V_P/V_S$ ratios (1.8–1.9), and laterally deformed crustal structures to reflect continental-to-oceanic transition. Low-velocity anomalies at shallow depths ($\le 3$ km) and strong velocity contrasts in the middle and lower crust correlate with sedimentary basins and major faults, indicating tectonic boundaries that influence regional seismicity. Coastal high-velocity anomalies at depth ($\sim$30 km) suggest localized mantle uplift related to rifting. Moho uplift near the coast, together with the asymmetric uplift of the Taebaek Mountain Range, indicates depth-dependent lithospheric stretching and isostatic rebound during rifting. These observations are consistent with geological evidence of East Sea (Sea of Japan) opening, highlighting the offshore rift center and its influence on onshore crustal structure. The results provide new constraints on rift-related processes, including lithospheric thinning, mantle upwelling, and asymmetric rift-flank uplift, demonstrating the role of paleo-rift structures in controlling present-day seismicity.