Moho Depth Variations From Receiver Function Imaging in the Northeastern North China Craton and Its Tectonic Implications

A detailed knowledge of the crustal thickness in the northeastern North China Craton (NCC) is important for understanding the unusual Phanerozoic destruction of the craton. We achieve this goal by employing a 2-D wave equation-based migration method to P receiver functions from 198 broadband seismic stations, using Ps conversions and surface-reflected multiples. By combining receiver function images along 19 profiles, we constructed a high-resolution Moho depth model for the northeastern NCC. The results present dominant E-W Moho depth variations similar to previous observations and new regional N-S variations beneath both sides of the North-South Gravity Lineament. To the west, while a deeper Moho (∼42 km) appears in the interior of the Trans-North China Orogen, a relatively shallow Moho (∼38 km) exists in the northern margin of the Trans-North China Orogen to western NCC. To the east, the crust beneath the Yan Mountains in the marginal area is thicker (∼32–40 km) than that (∼26–32 km) beneath the Bohai Bay Basin in the craton interior, and the Moho further shallows from NE (∼32 km) to SW (∼26 km) within the basin. Along with other observations, we conclude that the dominant E-W difference may have been associated with the Paleo-Pacific plate subduction under eastern Asia since the Mesozoic. The newly observed complex N-S variations may have reflected the structural heterogeneity of the cratonic lithosphere inherited since the formation of the NCC in the Paleoproterozoic, or spatially uneven effects on the cratonic lithosphere of subsequent thermotectonic events during the long-term evolution of the craton, or both.