Continent‐Side Uplifted Mantle and Geological Imprints Along a Paleo Rift in the Western East Sea (Sea of Japan)

Abstract

AbstractWe investigate the continent‐size lithospheric structures of paleo rift around the central Korean Peninsula using ambient noise tomography and earthquake‐based Eikonal tomography based on dense seismic networks. We determine Rayleigh‐wave group velocities at periods of 1–15 s from ambient noise tomography and Rayleigh‐wave phase velocities at periods of 20–80 s from earthquake‐based Eikonal tomography. We determine a 3‐D shear‐wave velocity model in the lithosphere from the Rayleigh wave velocities. The model exhibits high lateral variations ranging from ‒9% to 8%, depending on depth. The shear‐wave velocities at shallow depths (2 km) are relatively high in mountain regions and low in coastal and basin regions. Strong velocity contrasts are observed around major earthquake hypocenters at depths of 3–20 km, which may be due to the presence of seismogenic faults. Shear‐wave velocities at depths of 30–40 km are high along the east coast, suggesting uplifted mantle that is responsible for the opening of the East Sea (Sea of Japan). High velocity structures beneath Moho around the coast may suggest solidified underplated magma caused by the paleo rifting. The root of coast‐parallel high‐mountain range (Taebaek Mountain Range) is bounded by the uplifted mantle, presenting mountain range development in rift flank along paleo‐rift axis. Low shear‐wave velocities along the coast at depths km may imply elevated temperature beneath the solidified underplated magma. The continent‐side paleo rift affects the geological, thermal, and seismological properties around the continental margin at present.