EAPSI: Characterizing the Structural Evolution of the Longmen Shan Fault Zone in Eastern Tibet

Creason Christopher G, Corvallis OR

Investigators

Abstract

On May 12, 2008, a Mw 7.9 earthquake devastated the Longmen Shan region of Sichuan, China, near the eastern margin of the Tibetan Plateau. The earthquake resulted in numerous casualties and extensive damage to the regional infrastructure. Despite decades of research, the tectonic history of this seismically active region remains poorly understood. This project, by PI C. Gabriel Creason, seeks to improve our understanding of the geologic evolution of the Longmen Shan fault zone by better constraining the movement of its major faults. The project will be a joint effort between the PI and host researcher Dr. Erchie Wang, a Senior Researcher at the Institute of Geology and Geophysics, Chinese Academy of Sciences, and renowned scientist in the field of Tibetan geology. The objectives of this collaborative effort are two-fold: 1) construct geologic-cross sections in order to refine interpretations of regional geology of the Longmen Shan; and 2) during a two-week field campaign, interpret the local stratigraphy and structural geology of the area. Additionally, the project will also serve as a backdrop to strengthen ongoing international collaboration between research groups. Understanding when and how the Longmen Shan region reached its high modern elevation (>5000 m) are intrinsic questions that underlie broader questions in the fields of tectonic geomorphology (e.g., characterizing the topographic and structural response of the Tibetan Plateau to the northward incursion of the Indian continent) and seismology (e.g., assessing seismic hazard in regions with active tectonics). Thus, the overarching goal of this research is to reconstruct the magnitude and kinematics of Cenozoic fault slip along the Pengguan, Biechuan and Wenchuan faults located within the Longmen Shan. Several geologic cross-sections demonstrating the tectonostratigraphic framework of these faults will be constructed with the collective aim to better elucidate the region?s Cenozoic evolution. Data collected during fieldwork will be used to test for correlations between Cenozoic deposition of sediments and exhumation of the range-front to the west, and, subsequently, to assess the possibility of a linkage between fault motion, exhumation, and sedimentary deposition. This award under the East Asia and Pacific Summer Institutes program supports summer research by a U.S. graduate student and is jointly funded by NSF and the Ministry of Science and Technology of China.