Crustal structure beneath the North China Craton from joint inversion of ambient noise and receiver function

We collected waveforms from 188 broadband seismic stations deployed in the North China Craton (NCC). Based on these data, we obtained the sediment thickness, crustal thickness, and S-wave velocity structure of the crust in the study area through the joint inversion of ambient noise surface wave data and receiver function data. The results demonstrate: (1) The sediment thickness corresponds to the geological structure. (2) The crustal thickness changes from 29 km to 46 km, thinning sharply when moving northwest to southeast. (3) In the middle and upper crust, the North China Basin (NCB) shows slight high-speed anomalies, which may be related to the relatively high rock strength caused by multiple subsidence since the Cenozoic. (4) In the lower crust, the low velocity anomalies are found around the Tangshan-Tianjin, Zhangbei and Taihang Mountain orogenic belt. A significantly high-velocity anomaly is observed beneath the NCB, and we speculate that it may be caused by the underplating and crystallization of the basic mafic magma from the mantle, accompanied by large-scale extension after the lower crust detachment. (5) Located in several regions with strong earthquakes, there is a certain range of (similar to 10 km) high-speed bodies under the sedimentary layer, where the high-speed bodies are wrapped by the low S-wave velocity under them. The difference of rock strength in the crust provides conditions for stress accumulation and earthquake occurrence.