Late Quaternary Slip Rates and Holocene Paleoearthquakes of the Eastern Yumu Shan Fault, Northeast Tibet: Implications for Kinematic Mechanism and Seismic Hazard

Date: 4/24/2019

Time: 10:45 AM

Room: Vashon

The Yumu Shan (YMS) fault zone locates at the front of northeastward expansion of the Tibetan Plateau, where it is characterized by actively growing fault-related folds and northeast-vergent thrusts or buried faults, accompanying with strong earthquakes. The YMS fault zone is expressed by arc-shaped fault line and can be divided into two segments: the northern and eastern YMS faults. Numerous studies indicated that the northern YMS fault is marked by left-lateral strike-slip with a reverse component and has two paleoearthquakes in the Holocene. But the studies on the eastern YMS fault were conducted in the nineties of the 20th century, and the limitation of dating and survey techniques led to a big uncertainty in fault slip rates and paleoseismological results. In addition, the kinematic mechanism of the arc-shaped YMS fault zone remains unknown. In this study, combined with the interpretation of high-resolution satellite imagery, real-time kinematic (RTK) GPS survey, optically stimulated luminescence (OSL) and Accelerator Mass Spectrometry (AMS) radiocarbon dating of deformed landforms and trenching, we study slip rates and paleoseismology along the eastern YMS fault. Our results show that its Late Quaternary vertical and horizontal slip rate is ~0.3-0.4 mm/yr and ~1.1±0.1 mm/yr, respectively. At its northwest tip, the fault becomes dominantly reverse with a vertical rate of ~0.4 mm/yr. Trenching studies indicate that two events rupture the eastern YMS fault occurring at 7.37-5.24 ka and 5.17-4.01 ka, respectively. The eastern YMS fault may behave synchronously or interact with the northern YMS fault. We propose that the arcuate structure under the perpendicular compression to the arch apex can explain the kinematic mechanism of the arch-shaped YMS fault zone.

Presenting Author: Junjie Ren

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