Crustal thickness and Poisson's ratio in southwest China based on data from dense seismic arrays

Abstract

AbstractCrustal thickness and Poisson's ratio are important parameters to characterize regional isostasy state and material composition or state. Using the teleseismic waveform data from 141 permanent stations and 785 temporary stations in southwest China, we obtain the crustal thickness and average Poisson's ratio by theH‐κstacking of receiver functions. In the west (the SE Tibetan Plateau and the Yunnan‐Burma‐Thailand block) and southeast (the Cathaysian block and southern Yangtze craton) of the study region, there are high correlation coefficients for the crustal thicknesses between what we obtain from the receiver functions and what we calculate from the Airy isostasy model, indicating that a state of isostasy can be achieved at the crust‐mantle boundary beneath these two regions. In the northeast (northern Yangtze craton), the correlation coefficient is lower, indicating that the effect of the lithosphere needs to be considered for a regional isostasy. Intermediate Poisson's ratios (0.26 ≤ σ ≤ 0.28) are found beneath the northern Panzhihua‐Emeishan region. Combing the high‐velocity features from previous study, we speculate that it may be related to the Emeishan large igneous province. High Poisson's ratios (σ > 0.28) are found beneath the SE Tibetan Plateau and the nearby strike‐slip faults, such as the Anninghe‐Zemuhe fault and the northern Xiaojiang fault. Combing the low‐velocity zones from previous study, we speculate that there may be partially melted and lower crustal flow.