Mantle transition zone imaging beneath the East Sea (Sea of Japan) using teleseismic receiver functions

The mantle transition zone (MTZ), bounded by seismic discontinuities near 410 and 660 km depth, plays a key role in mantle convection by regulating heat and material exchange between the upper and lower mantle. In this study, we image the MTZ structure beneath the East Sea (Sea of Japan) using common conversion point (CCP) stacking of teleseismic receiver functions from a dense array of broadband stations located on the Korean Peninsula and the Japanese Islands. The resulting CCP-stacked images reveal a generally thickened MTZ, likely reflecting the presence of the stagnant Pacific slab at the base of the MTZ. In contrast, a near-normal MTZ thickness is observed beneath Ulleung Island, potentially indicating localized thermal or compositional heterogeneity. These findings allow us to assess the relationship between MTZ structure and major tectonic processes in East Asia, providing constraints on mantle temperature, composition, and volatile content.