Seismic constraints of thinning and fragmenting continental lithosphere beneath the Korean Peninsula

Modification of the continental lithosphere is still an enigmatic process. The Korean Peninsula (KP) is one of ideal place to depict the process by interactions with subducting oceanic slabs. We detect a significant thickness change (>50 km) of the continental lithosphere beneath the KP that is confirmed by two independent approaches: (1) 3D imaging using ambient noise analysis and (2) receiver function CCP stacking. A series of transdimensional and hierarchical Bayesian joint inversions is performed to obtain a high-resolution 3D model from different types of surface wave dispersion data. For the stacking of receiver function waveforms, the coda waveforms of crustal multi-modes (PpPs and PpSs) are combined together to better image the lithosphere-asthenosphere boundary. We estimate the relatively deeper rooted lithosphere (>100 km) in the southwestern part of the KP compared to shallower surrounding regions. The lithospheric structure is underlain by lower velocity anomalies (Vs<4.1 km/s), which extends from back-arc regions near subducting slabs horizontally and connects to low velocity anomalies in the deeper upper mantle vertically. The imaged features clearly show that the effect of the oceanic slab subduction is a key factor controlling the modification process. We further examine the implication for the occurrence of intraplate volcanoes and the relationship to the mantle transition zone heterogeneities due to stagnant slabs in the northeast Asia.