Limit on slip rate and timing of recent seismic ground-ruptures on the Jinghong fault, SE of the eastern Himalayan syntaxis

• Main Authors: Shi, Xuhua, Weldon, Ray, Liu-Zeng, Jing, Wang, Yu, Weldon, Elise, Sieh, Kerry, Li, Zhigang, Zhang, Jinyu, Yao, Wenqian, Li, Zhanfei
• Other Authors: Earth Observatory of Singapore
• Format: Article
• Language: English
• Published: 2019
• Subjects: Eastern Himalayan Syntaxis; Shan Plateau; Science::Geology
• Online Access: https://hdl.handle.net/10356/107492; http://hdl.handle.net/10220/49710
• Institution: Nanyang Technological University

Quantifying slip rates and earthquake occurrence of active faults on the Shan Plateau, southeast of the easternHimalayan syntaxis, is critical to assessing the seismic hazard and understanding the kinematics and geody-namics of this region. Most previous estimates of slip rates are averaged over either many millions of years usingoffset geological markers or decades using GPS. Well-constrained millennial slip rates of these faults remainsparse and constraints on recurrence rates of damaging earthquakes exist only for a few faults. Here we in-vestigate the millennial slip rate and timing of recent earthquakes on the Jinghong fault, one of the geomor-phically most significant sinistral-slip faults on the central Shan Plateau. We map and reconstruct fault offset(18 ± 5 m) of alluvial fan features at Manpa on the central Jinghong fault, using a 0.1 m-resolution digitalsurface model obtained from an unmanned aerial vehicle survey. We establish a slip rate,≤2.5 ± 0.7 mm/yrover the past ~7000 years, using pit-exposed stratigraphy. This millennial slip rate is consistent with ratesaveraged over both decadal and million-year timescales. Excavations at three sites near the town of Gelanghe onthe northeastern Jinghong fault demonstrate 1) that the last seismic ground-rupture occurred between 482 and889 cal yr BP, most likely in the narrower window 824–767 cal yr BP, if the lack of large earthquakes in thehistorical earthquake record is reliable, and 2) that multiple fault ruptures have occurred since ~3618 cal yr BP.Combining thisfinding with a lack of large earthquakes in the ~800-year-long Chinese historic record in thisregion, we suggest an average recurrence interval of seismic ground-ruptures on the order of ~1000 years. Thisrecurrence interval is consistent with the slip rate of the Jinghong fault and the size and earthquake frequency onother sinistral faults on the Shan Plateau.