Moho Depth and Poisson's Ratio beneath Eastern-Central China and Its Tectonic Implications

Abstract:

Eastern-central China comprises a complex amalgamation of geotectonic blocks of different ages and undergone significant modification of lithosphere during the Meso-Cenozoic time. To better characterize its deep structure, we estimated the Moho depth and average Poisson's ratio of eastern-central China by H-κ stacking of receiver functions using teleseismic data collected from 1196 broadband stations. A coexistence of modified and preserved crust was revealed in eastern-central China, which was generally in Airy-type isostatic equilibrium. Crust is obviously thicker to the west of the North-South Gravity Lineament but exhibits complex variations in Poisson's ratio with an overall felsic to intermediate bulk crustal composition. Moho depth and Poisson's ratio show striking differences as compared to the surrounding areas in the rifts and tectonic boundary zones, where earthquakes usually occur. Similarities and differences in the Moho depth and average Poisson's ratio were observed among the Northeast China, North China Craton, South China, and the Qinling-Dabie Orogen as well as different areas within these blocks, which may result from their different evolutionary histories and strong tectonic-magma events since the Mesozoic. In addition, we observed an alteration of Moho depth by ~6 km and of Poisson's ratio by ~0.03 as well as striking E-W difference beneath and across the Xuefeng Mountains, suggesting that the Xuefeng Mountains may be a deep tectonic boundary between the eastern Yangtze Craton and western Cathaysia Block.