The characteristics of S-wave and the crust structures in the nearby DaBie orogenic belt
Changfeng - Anyi Deep Seismic Sounding profile goes across three geotectonic units. that are North China Block, Dabie Orogenic Belt and Yangtze Block, the whole profile is about 420 kilometer long. S-wave's information is very rich on the eight pieces of the seismic record sections.According to S-wave data, the crust can be divided into three layers, Moho boundary is 33 to 41 kilometer, that is 41 kilometer in nearby the Yuexi region, and there exists a mountain root of 6 ? deep below the Dabie oro-genic belt.On the basis of P-wave and S-wave velocity, the Poisson's ratio of the crustal rocks are calculated, and the composition of the rocks in the middlelower crust ate estimated. The P-wave velocity and Poisson's ratio is 6. 2 -6. 3km/s and 0. 24 - 0. 25 respectively , that is corresponding to granite, granodiorite, felsic amph. facies gneiss and quartz-mica schist in the middle crust. The P-wave velocity and Poisson' s ratio is 6. 5 - 6. 6km/s and 0. 24 - 0. 26 respectively , that is corresponding to intermediate granulite in the lower crust. The above results have shown that are probably the acidic rocks to neutral rocks below the middle-lower crust of the Dabie orogenic belt.The S-wave splitting phenomenon is found in the polarized analysis of the typical S-wave groups, and the polarized eirection of the faster S-wave is usually corresponding to the direction of the main horizonal stress. The polarized feature of the faster S-wave in this region has shown that the direction of main horizonal stress with the Yangtze Block, Dabie Orogenic Belt and North China Block is N77°E, N18°W and N53°E respectively.
【CateGory Index】： P542