Three‐Dimensional Seismic Transmission Tomography of the Deep Earthquake Faults in Yinchuan Basin

Abstract

AbstractIn order to prove the validity and application value of three‐dimensional seismic transmission technology in active fault detection, a seismic array was deployed in the middle and 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 from Luhuatai to Xidatan, and its depth reaches 7 km there. The Luhuatai fault, Yinchuan‐Pingluo fault, and Huanghe fault all appear as NNE‐trending velocity difference strips and there is significant variation in the depth of sediment interface across the faults. 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 the distribution and shallow features of the major faults, but also their extension under the basement.