The Crustal Thickness And Poisson’s Ratio In The Junction Of The Taihangshan Region And The Yanshan Tectonic Belt

The junction of the Taihangshan region and the Yanshan tectonic belt traverses the North China Craton from east to west and crosses the North-South Gravity Gradient Lineament in the middle. The information related to the formation and evolution of the North China Craton recorded in its crustal structure has vast importance to the study of the North China Craton’s destruction. In recent years, the receiver function method has been widely used in the study of crust and upper mantle structure, to obtain more accurate information of crustal thickness and wave velocity ratio. Different researchers have used the receiver function of the H-κ method to study crustal thickness and Poisson’s ratio of the North China area. However, due to the sparseness of permant seismic stations and the limited distribution of portable seismic stations around the Taihangshan and Yanshan tectonic belts, the published crustal results are not good enough to constraint the tectonic evolution information of the junction of the Taihangshan region and Yanshan tectonic belt.In this study, we collect waveforms of worldwide teleseismic events with magnitudes greater than5.5recorded by192seismic stations from the Beijing metropolitan Digital Seismic Network (BDTSN) and4temporary broadband seismic arrays deployed in the junction of the Taihangshan region and the Yanshan tectonic belt during different periods of2001-2013. Using the receiver functions of the H-κ and CCP stacking methods, we obtain the crustal thickness and average Poisson’s ratio beneath134stations deployed on bedrocks.The comparison of our results of the H-κ and CCP stacking methods shows that our results are self-consistent and in conformity with the previous studies as well, which means reliable. Comprehensive analyzing the fine crustal constraints distribution information in this study, we conclude that (1) the crustal thickness of our study area gradually decreases from northwest to southeast overall; there is a distinct small scale differentiation on both sides of the North-South Gravity Lineament and its nearby regions.(2) the spatial distribution of average Poisson’s ratio in this region is quite nonuniform; there is significant difference on both sides of the North-South Gravity Gradient Lineament, which indicates the crustal material compositions has obvious regional difference.(3) the Airy equilibrium relationship of elevation and crustal thickness demonstrates that the crust of this region has not yet reached the Airy equilibrium state.(4) the strong earthquake activities are closely related to the spatial differentiation of the Poisson’s ratio and the difference of crustal medium properties and middle-upper crustal structure.(5) the crustal thickness and Poisson’s ratio can be divided into2relative aggregated group. Though they decrease linearly with the increase of crustal thickness slowly, they may reflect that those areas experienced distinct process of crustal modification in the tectonic evolution process of the North China Craton.