A study of upper mantle discontinuities beneath the Korean Peninsula

Abstract

The study on the topography of the upper mantle discontinuities helps us to understand thecomplex interactions between the subducting slabs and upper mantle discontinuities. Toinvestigate the depth variation of the upper mantle discontinuities beneath the KoreanPeninsula and surrounding regions, we applied the common conversion point stacking of the Pto-s receiver functions. The broadband seismic networks in South Korea and Japan were usedto produce the high-resolution receiver function images of the region. The 410- and 660-kmdiscontinuities (hereafter referred to as the 410 and the 660) are clearly imaged and their depthvariations show interesting features, especially for the 660. In this region, the subducting Pacificslab bends to flatten over the 660 and several tomographic images indicate that the stagnantslab is extending to the west under China. If the depth of the 660 is affected by thetemperature, the broad depression of the 660 is expected and several SS precursor studiessupport this idea. However, our observation shows that the 660 is locally depressed and itspattern is spatially changing. While the depressed 660 due to the Pacific slab is clearly imagedat lower latitudes (< 37°N), there is no evidence of the depressed 660 to the north. It indicatesthat the effect of the Pacific slab on the depth variation of the 660 is changing significantly inour study area.