Millennial slip rates and paleoseismology of the Jinghong fault on the Shan Plateau, southeast of the eastern Himalayan syntaxis
Abstract
The Shan Plateau, southeast of the eastern Himalayan syntaxis, has developed a system of sinistral faults that have experienced complex kinematic histories associated with the tectonic evolution of the Indian-Asia collision. Assessing the seismic hazard and understanding the geodynamic mechanisms of these faults requires constraints on the slip rates and their variation in time and space. Previously we constrained the geodetic total slip rates across the fault system to 12 mm/yr, consistent with long-term slip rates obtained from geologic offsets averaged over 10 Ma. Well constrained millennial slip rates of these faults remain sparse. Here we chose one of the fastest-slipping faults, the Jinghong fault (JHF), to constrain its millennial rates and paleoseismology. We used a high-resolution digital elevation model (DEM) obtained from an unmanned aerial vehicle (UAV) survey and ALOS 5 m DEM to reconstruct the fault offsets at the Manpa site in central JHF, and at Nange and Yumu sites in the eastern JHF. We also refined mapping of offset landforms using trench-exposed stratigraphy. In central JHF, both the UAV-DEM and stratigraphy enabled our recognition and mapping of older and younger phases of fan development. The contact between these two serves as an offset piercing line. Our geomorphic and stratigraphic correlation yielded an upper bound of 18±5 m for the offset of the contact. The best constraint on the 14C age of the fan contact is 7138±113 cal years BP, from a charcoal sample near the cobble and boulder-bearing bottom of the channel in the younger fan. Dividing the 18-m offset by this age yields a preliminary slip rate of ≤ 2-3 mm/yr along the central JHF. This rate is consistent with decadal and million-year-averaged rates of the JHF, suggesting a relatively constant fault slip rate through time. In the eastern JHF, field mapping and the ALOS DEM constrained the fault offsets at Nange and Yumu sites to 70±10 m and 100±15 m, respectively. These results combined with the timing of the fault offsets to be determined by optically stimulated luminescence (OSL) dating will enable us to evaluate whether fault slip rates are uniform in time and space along the JHF. Finally, our paleoseismological excavation at two sites in eastern JHF will provide the dates of last earthquakes occurring in the eastern section of the JHF.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.T13D..01S
- Keywords:
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- 7221 Paleoseismology;
- SEISMOLOGYDE: 7230 Seismicity and tectonics;
- SEISMOLOGYDE: 8107 Continental neotectonics;
- TECTONOPHYSICSDE: 8175 Tectonics and landscape evolution;
- TECTONOPHYSICS