American Geophysical Union Become an AGU Member
Subscribe to AGU Journals		 AGU Home AGU Publications

Read Full Article (file size: 1596232 bytes)    Cited by

TECTONICS, VOL. 26, TC4005, doi:10.1029/2006TC001987, 2007

Active tectonics of the Beichuan and Pengguan faults at the eastern margin of the Tibetan Plateau

Alexander L. Densmore

Institute of Hazard and Risk Research and Department of Geography, Durham University, Durham, UK


Michael A. Ellis

Center for Earthquake Research and Information, University of Memphis, Memphis, Tennessee, USA


Yong Li

National Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu, Sichuan, China


Rongjun Zhou

Seismological Bureau of Sichuan Province, Chengdu, Sichuan, China


Gregory S. Hancock

Department of Geology, College of William and Mary, Williamsburg, Virginia, USA


Nicholas Richardson

Department of Earth Sciences, Swiss Federal Institute of Technology, Zurich, Switzerland


Abstract

The steep, high-relief eastern margin of the Tibetan Plateau has undergone rapid Cenozoic cooling and denudation yet shows little evidence for large-magnitude shortening or accommodation generation in the foreland basin. We address this paradox by using a variety of geomorphic observations to place constraints on the kinematics and slip rates of several large faults that parallel the plateau margin. The Beichuan and Pengguan faults are active, dominantly dextral-slip structures that can be traced continuously for up to 200 km along the plateau margin. Both faults offset fluvial fill terraces that yield inheritance-corrected, cosmogenic 10Be exposure ages of <15 kyr, indicating latest Pleistocene activity. The Pengguan fault appears to have been active in the Holocene at two sites along strike. Latest Quaternary apparent throw rates on both faults are variable along strike but are typically <1 mm yr−1. Rates of strike-slip displacement are likely to be several times higher, probably ∼1–10 mm yr−1 but remain poorly constrained. Late Quaternary folding and dextral strike-slip has also occurred along the western margin of the Sichuan Basin, particularly associated with the present-day mountain front. These observations support models for the formation and maintenance of the eastern plateau margin that do not involve major upper crustal shortening. They also suggest that activity on the margin-parallel faults in eastern Tibet may represent a significant seismic hazard to the densely populated Sichuan Basin.

Received 28 April 2006; accepted 2 April 2007; published 17 July 2007.

Keywords: Tibetan Plateau; geomorphology.

Index Terms: 8107 Tectonophysics: Continental neotectonics (8002); 8111 Tectonophysics: Continental tectonics: strike-slip and transform; 7221 Seismology: Paleoseismology (8036); 1824 Hydrology: Geomorphology: general (1625).

Read Full Article (file size: 1596232 bytes)    Cited by

Citation: Densmore, A. L., M. A. Ellis, Y. Li, R. Zhou, G. S. Hancock, and N. Richardson (2007), Active tectonics of the Beichuan and Pengguan faults at the eastern margin of the Tibetan Plateau, Tectonics, 26, TC4005, doi:10.1029/2006TC001987.