关键词: 南天山, 地震构造, 深浅构造

Abstract: The interaction zone between southern Tianshan and northern Tarim locates at northeast side of Pamir. It is a region with high seismicity. We built a seismotectonic model for the west part of this zone from data of geological profiles, deep crust seismic detection and earthquake focal mechanisms in this paper. Geological profiles show different structure styles between the north of Artux anticline and the south of it. There are southward thrust blocks with basement rocks and strongly deformed Mesozoic and Cenozoic folds at the north, but northward reverse faults and flat Neogene - Quaternary shallow folds at the south. A fault named Qiligaike at the north side of the Artux anticline can be identified from its linear feature on satellite image. It cuts many folds at the north, and controls the twisting deformation of Artux anticline at the south. These deformation features on two sides of the fault imply the fault is a high angle strike-slip fault. Deep crust seismic detection also shows different velocity structures between Tianshan and Tarim Basin. Depth of the crystalline basement is 4km in Tianshan and 10km in Tarim; Depth of crust in Tianshan is 55km and 50km in Tarim. Steep slope of the crust exists at the northwest of Artux. These indicate the existence of high angle faults. Based on the synthesized geological features, deep crust structure, and earthquake focal mechanisms, we think that the main regional tectonic is featured as that the Tianshan tecto-lithostratigraphic unit overthrusts on the Tarim block. The Tianshan tectonic system includes the Maidan fault and thrust sheets in front of the fault; The Tarim tectonic system includes the underground northern Tarim margin fault, conjugate fractures in basement and overthrust faults in shallow. The northern Tarim margin fault is a high angle fault existing in deep of the Tarim crust, adjusting different trending deformation between Tianshan and Tarim. It is the major active fault that can generate large earthquakes. The other faults as the Tianshan overthrust system and the Tarim basement faults in this area may generate moderately strong earthquakes with different styles.

Key words: southern Tianshan, seismotectonic, shallow and deep structures