Study of crustal thickness and Poisson ratio of the North China Craton

The crustal thickness and physical properties of the North China Craton (NCC) are important for understanding the destruction of NCC. We collected waveforms of teleseismic events which occurred from August 2007 to March 2009 from 323 broadband seismic stations deployed in the NCC region. In order to obtain reliable receiver functions, the broadband seismograms of 93 teleseismic earthquakes occurred in the epicentral distance range from 30 degree to 95 degree with magnitudes M6.5 to M8.5 were collected. Based on these data, we calculated the receiver functions for each of the seismic stations, and inverted for the distributions of crustal thickness and Poisson ratio for the NCC with fine spatial coverage. There are three characteristics of the crustal thickness and the Poisson ratio: (1) Crustal thinning process not only occurs in the east part of NCC, but also extends to the North South Gravity Lineament. (2) Crustal thinning also occurs in the rifts and basins surrounding the Ordos block, and the Poisson ratio in the surrounding rifts is higher than that inside of the Ordos block. In some rifts the Poisson ratio is as high as 0.3. (3) The crustal thickness of NCC is negatively correlated to the topography, which is in consistence with Airy isostasy, which may imply that the NCC crust is experiencing a slow process of destruction and isostasy. While the isostasy degree is much lower in the central west and north east part of NCC.