Upper crustal structure of Haiyuan tectonic zone and its surrounding areas

By using the eight-shots of deep seismic sounding records from the Xiahe (Gansu Province) to Jingbian (Shaanxi Province) section, we get the upper crustal structure and basement depth of Haiyuan tectonic zone and its surrounding areas, which is a 650 km long profile. The result shows that, Qinling-Qilianshan folding zone in the west of Haiyuan tectonic zone has an obviously lateral heterogeneity in upper crust, the basement depth ranges from 1 to 5 km, which reveals that the zone has been destructed and deformed strongly. Whereas on the east side of Haiyuan tectonic zone, the Ordos block exhibits a homogeneous and stable upper crust, which has a 5-6 km depth crystalline basement and a relative low velocity gradient. Moreover, the upper crust of Haiyuan tectonic zone and the Haiyuan arcuate fault zone are the most strongly destructed and deformed areas along the profile. Therefore, the distinct difference in upper crust structure between the east and west side of Haiyuan tectonic zone reveals the cause of structural complexity and its relation with seismic activities.