Regional variation in Moho depth and Poisson's ratio beneath eastern China and its tectonic implications

Eastern 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 conducted H-κ stacking of receiver functions using teleseismic data collected from 1143 broadband stations and produced a unified and detailed map of Moho depth and average Poisson's ratio (σ) of eastern China. A coexistence of modified and preserved crust with generally in Airy-type isostatic equilibrium was revealed in eastern China, which correlates well with regional geological and tectonic features. Crust is obviously thicker to the west of the North-South Gravity Lineament but exhibits complex variations in σ with an overall felsic to intermediate bulk crustal composition. Moho depth and σ values show striking differences as compared to the surrounding areas in the rifts and tectonic boundary zones, where earthquakes usually occur. Systematic comparison of Moho depth and σ values demonstrated that there are both similarities and differences in the crustal structure 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. Using new data from dense temporary arrays, we observed a change of Moho depth by ∼3 km and of σ by ∼0.04 beneath the Tanlu Fault Zone and an alteration of Moho depth by ∼5 km and of σ by ∼0.05 beneath the Xuefeng Mountains. In addition, striking E-W difference in crustal structure occur across the Xuefeng Mountains: to the east, the Moho depth is overall <35 km and σ has values of <0.26; to the west, the Moho depth is generally >40 km and σ shows complex and large-range variation with values between 0.22 and 0.32. These, together with waveform inversion of receiver functions and SKS shear-wave splitting measurements, suggest that the Tanlu Fault Zone is at least a crustal-scale fault and the Xuefeng Mountains may be a deep tectonic boundary between the eastern Yangtze Craton and western Cathaysia Block.