Tomographic determination of the deep earthquake faults in Yinchuan basin by using three-dimensional seismic transmission technology
银川盆地深地震断层的三维透射成像

In order to prove the validity and application value of three-dimensional seismic transmission technology in active fault detection, a three-dimensional seismic transmission array was deployed in the middle north of Yinchuan basin. The basement and upper crust structure under the seismic array were reconstructed based on first-arrival refraction traveltimes and reflection traveltimes from Moho at critical distances by using finite difference method, time-term method and the inversion method without model blocks. The results show that the basement of the studied area is shallow in the east and west and deep in the centre and it is steeper in the west than in the east. The greatest depth of the basement occurs between Luhuatai to Xidatan, and its depth reaches 7 km there. Luhuatai fault, Yinchuan-Pingluo fault and Huanghe fault all behave as velocity difference strip of NNE direction and there is significant variation in the depth of the sediment interface. The east-dipping, high-angle Luhuatai fault extends under the basement. The west-dipping Yinchuan-Pingluo fault is a buried fault penetrating the basement. Huanghe fault dips toward the west and penetrates the basement as well. These exploration results prove that the three-dimensional seismic transmission technology, which combines first-arrival refraction wave exploration with Moho reflection wave exploration, is applicable in the reconstruction of fine upper crustal image of the studied area. With this technology, we can not only reveal distribution and shallow features of the major faults, but also their extension under the basement.