Seismic shear wave reflectivity structure of the mantle beneath northeast China and the northwest Pacific

Using multiple ScS reverberations, we examine the mantle reflectivity structure beneath northeast China and the northwest Pacific. We find several upper mantle discontinuities, including a melt layer with a mean thickness of 64 km atop the 410 km discontinuity, present on both sides of the subducting slab near the Nankai trench. The transition zone contains a split 520 km discontinuity in several paths, and tomographic images show stagnant slabs at this depth. We believe that this may be slab related based on experimental work. A negative reflector is found in one path beneath the northeast China craton at a depth of 598 km. Mid-mantle reflectors are found in all of our paths and are present throughout a wide depth range (~750-1600 km). Key Points The LAB appears depressed beneath northeast China Splitting of the 520-km might be related to exsolution of Ca-perovskite Mid-mantle reflectors are ubiquitous in the region