The tectonic activity and deformation features during the Late Quaternary of Elashan Mountain active fault zone in Qinghai Province and its implication for the deformation of the northeastern margins of the Qinghai-Tibet Plateau
YUAN Dao-yang~(1,2), ZHANG Pei-zhen~2, LIU Xiao-long~1, LIU Bai-chi~1, ZHENG Wen-jun~1, HE Wen-gui~1 (1. Lanzhou Base of Institute of Earthquake Prediction, CEA, Lanzhou 730000, China; 2. State Key Laboratory of Earthquake Dynamics, Institute of Geology, CSB, Beijing 100029, China)
The Elashan Mountain active fault zone is an important boundary between the Qaidam basin in the west and the Chaka-Gonghe basin in the east in Qinghai-Tibet Plateau. This fault is about 207 km long and mainly consists of six discontinuous sub-parallel strands with either right-step or left-step echelon separating each apart. The step distance is about 1～3.5 km. The initiation of right-lateral strike slip motion is in about 1.8～3.8 Ma, i. e. the Early Quaternary. The offsets of the large geological body, e. g. Paleozoic geological contacts and Mesozoic granites, are about 9～12 km. The Late Quaternary tectonic activity is characterized by both right-lateral strike-slip and NEE-direction crustal shortening. The average right-lateral strike-slip rate of the Elashan Mountain active fault zone is about 4.1±(0.9) mm/a and the vertical slip rate is 0.15±0.1 mm/a since the Late Pleistocene. The deformation of the Elashan Mountain area, under the action of NE direction regional structural stress and right-lateral shear and compression, formed the strike-slip compressive basins: the Wulan basin and Chaka-Gonghe basin that developed on the east and west side of the Elashan Mountain active fault zone, respectively. It appears that the NE Qinghai-Tibet Plateau has subjected to NE-direction compression resulting in both conjugate shear and compression. Thus, the NNW-trending fault had right-lateral displacement, and the NWW-trending faults had left-lateral offset as well as compression. This pattern of deformation suggests that NE-direction crustal shortening may accommodate large amounts of regional deformation, and that the eastward extrusion appears to be insignificant.
【Fund】： 国家自然科学基金项目(40372086);; 国家自然科学基金重点项目(40234040);; 国家重点基础研究发展规划项目(G1998040701);; 中国地震局兰州地震研究所论著号:LC20040041
【CateGory Index】： P542
【CateGory Index】： P542