Abstract: Taking Lixian-Luojiabao fault as a causative fault of an Mw 7.7 scenario earthquake, a hybrid numerical method combining finite difference method with random vibration synthesis method is adopted to simulate broadband ground motion field in Tianshui basin, and the ground motion characteristics in the basin are analyzed, providing ground motion parameters for analyzing seismic loess landslides. The following conclusions are acquired:(1)Finite difference method and random vibration synthesis method are complementary to get broadband ground motion in the basin. (2)The scenario earthquake causes intensive ground motion in the basin, with PGA (peak ground acceleration) of 150~900 gal. The largest PGA is located in the southeastern corner of the basin where is nearest to causative fault, and it decreases with the distance from causative fault. Compared to the north side of river valley, the south side has larger PGA to induce landslides. (3)The largest PGV is 120cm/s in the basin. Affected by Quaternary covering layer amplification effect and terrain amplification effect, PGV in the east and the central parts of the basin are larger than those in the west part. (4)The vertical ground motion shows smaller PGV in the east part of the basin but larger ones in the west and central parts. Especially at the western most steep mountains, PGV reaches the maximum. In addition, the vertical ground motion can also reflect the influence of loess layer, for example, the PGV is also larger in the central part of the south side of the basin.