南天山及塔里木北缘构造带西段地震构造研究

SEISMOTECTONIC STUDY ON WEST PART OF THE INTERACTION ZONE BETWEEN SOUTHERN TIANSHAN AND NORTHERN TARIM

南天山及塔里木北缘构造带位于帕米尔地区东北侧,地震活动强烈。文中通过地质构造剖面、深部探测资料和地震震源机制解资料,综合研究了该区的地震构造模型。结果认为,该区的构造活动主要表现为天山地块逆冲于塔里木地块之上。天山构造系统包括迈丹断裂及其前缘推覆构造;塔里木构造系统包括深部的塔里木北缘断裂、基底共轭断层和浅部的推覆构造。塔里木北缘断裂是发育于塔里木地壳内部的高角度断裂,其形成原因在于塔里木和天山构造变形方向的差异。塔里木北缘断裂为研究区大地震的主要发震构造,天山推覆构造和塔里木基底断裂系统均具有不同性质的中强地震发震能力。

The interaction zone between southern Pamir. It is a region with high seismicity. zone from data of geological profiles, deep c this paper. Tianshan and northern Tarim locates at northeast side of We built a seismotectonic model for the west part of this rust seismic detection and earthquake focal mechanisms in 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.