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An Overview of Activity Rate Along the East Kunlun Fault Zone
LI Jian-jun, LI Wen-qiao, GONGQIU Zhuo-ma, SIJIN Luo-bu, CIREN Duo-ji, LI Jia-yi, ZHANG Jun-long
2024 (1):
118-140.
doi: 10.12196/j.issn.1000-3274.2024.01.009
Since the neotectonic period, the Qinghai-Tibet Plateau has undergone intense uplift and eastward sliding. The East Kunlun Fault Zone (EKF) is one of the major sinistral strike-slip faults in the Qinghai-Tibet Plateau. Its rate of activity has become one of the key data to understand this process. In recent years, the EKF activity rate has been obtained through methods such as remote sensing, geological surveys, paleoearthquakes, and geodesy. The time scale of different research methods ranges from decades to tens of thousands of years. Therefore, the differences in results and their reasons can be analyzed from different disciplines. Furthermore, it is formed through a phased understanding of the variation in the EKF activity rate. The results show that the EKF exhibits typical strike-slip fault geometry. Its structure changes from simple to complex “horse-tail” shaped forms as one moves from west to east. The eastern endpoint is limited by the structural trend change zone between the EKF, Minjiang Fault, and Longmenshan Fault. The horizontal slip rate decreases overall from west to east. Taking the Animaqing Mountains (99°E~100°E) as the boundary, the horizontal activity rate in the western region is basically stable at 10~12 mm/a, with little change, and the horizontal activity rate in the eastern region is 1~12 mm/a, which is not greater than that in the west, but is more controversial. In the case of similar geomorphological dislocations and geodetic data, the difference in activity rates may be related to the difference in the initial age of dislocations and the post-earthquake viscoelastic relaxation effect. Most of the reduced activity rate may be due to secondary faults of the East Kunlun fault and internal faults of the Bayan Har block, or to the Minshan uplift on the east side. Sporadic results show that the vertical motion rate on the west side is about 10% of the horizontal activity rate, while the vertical motion rate on the east side gradually increases. This indicates that part of the horizontal deformation on the west side is still converted to vertical uplift on the east side. At present, when the horizontal motion of the East Kunlun fault zone has been studied in depth, future research can try to supplement the study of vertical motion and use the change of the ratio of horizontal and vertical velocities to explore the transformation process of horizontal strike-slip and vertical uplift deformation. Different disciplines have different understandings of the EKF activity rate, which is due to the complex geometric structure of the fault zone and differences in research methods across disciplines on the spatiotemporal scale.
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