Abstract:

The continental margin of southeastern China has undergone complex tectonic evolution since the Mesozoic, especially during the Late Mesozoic under intense magmatic activities. Here, we determine the crustal thickness and the average Poisson’s ratio for crust to better understand crust-mantle interaction and related geodynamic processes in this region. Teleseismic waveform data were collected from 90 permanent seismic stations deployed in Fujian, including 2 deployed by researchers from Taiwan, China. The crustal thickness and the average Poisson’s ratio of crustal rocks were calculated by H-κ stacking method using teleseismic P-wave radial receiver functions. Combining the calculation results with previous observation results by portable stations, high-resolution distribution maps of crustal thicknesses and Poisson’s ratios were obtained, which show the continental crust is generally thin, with crustal thickness ranging from 28.0 to 34.1 km (averaging 31.0 km), and Poisson’s ratio ranging from 0.22 to 0.29; the Moho interface in the study area is gently undulating, with overall thinning from inland to the coast, and Moho offsets beneath some faults were observed. The coastal area along the continental margin is situated on thin continental crust, not the transition zone between continental and oceanic crusts. The Fu’an-Nanjing fault zone is a vitally important fault zone in the region. The crustal thickness and Poisson’s ratio for crust have a positive correlation in the coastal Fujian-Zhejiang volcanic-intrusive rock belt to the east of the fault zone and a negative correlation in the inland Cathaysia block to the west of the fault zone. Compared to inland, Poisson’s ratio for crust in the coastal area is generally higher, which may be related to Late Mesozoic magmatic underplating and the development of low-velocity thin layers within the crust in the coastal area.

Key words: continental margin of Southeast China, receiver functions, crustal thickness, Poisson’s ratio, Fu’an-Nanjing fault