Seismic hazard analysis for a grand bridge site in the northern Tianshan region of Xinjiang

The Tianshan orogen in northwest China experiences frequent earthquakes. In recent years, there has been an increase in major bridge projects constructed on complex geological sites in border areas. Conducting a seismic hazard analysis for bridge site regions is crucial to ensure structural serviceability and risk resistance. This study takes the G577 highway built in the Tianshan region of Xinjiang as an example to carry out regional seismic structure and activity investigation, and takes the Jingsigebulake bridge of the line as an example to carry out probabilistic seismic hazard analysis (PSHA). The research shows that the seismic activity in Tianshan region is frequent, and 627 earthquakes with magnitude ≥ 5 are recorded in areas affecting engineering construction. The shallow earthquakes with a depth of less than 30 km are the main ones, and the seismic source mechanism is mostly reverse strike-slip fault dislocation. Regional neotectonic movements exhibit significant north-south variations in vertical uplift and subsidence, as well as horizontal compressive effects, and the coexistence of intermittent movement and inheritance-regeneration of movement mode. The fault zones are well developed in the region, which are concentrated in the Tianshan Mountains and the northern and southern margins of the Ili Basin. The faults near the highway project are mainly along the NWW direction. Based on the seismic structure and activity records, it is considered that the site of Jingsigebulake bridge is located in the intensity Ⅷ region. The ground motion parameters of the bridge site were determined by PSHA, and the correlation between seismic intensity, exceedance probability and peak ground acceleration was established. The research can provide reference for regional development and engineering construction in Tianshan region of Xinjiang.