B.C. Burchfiel et al., Dept. of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA. Pages 4-11.
Here is the first authoritative treatment of the geological and geophysical context of the 12 May 2008 magnitude 7.9 earthquake that shook the eastern Tibetan Plateau, killing more than 65,000 people. The paper is by a coalition of MIT geologists and geophysicists who have worked in the region for many years, together with their long-time Chinese colleagues from the Chengdu Institute of Geology and Mineral Resources, Sichuan, China. The setting for the earthquake is that of large-scale mountain-building, surface uplift, and right-lateral movement of the eastern Tibetan Plateau relative to southeast China. Several faults are likely candidates for movement, including the northeast-trending Beichuan and Wenchuan faults. Crustal shortening in this region is very slow, around 1 mm/yr (plus or minus 1 mm/yr) and, with its low seismicity, this area was considered to be of low seismic risk compared to surrounding areas. However, the slow shortening, ductile thickening in the deep crust, and the large elevation difference between the Tibetan plateau and the adjacent lowlands probably created large stresses in the upper crust near the edge of the plateau. GPS-determined convergence rates in the vicinity of the 12 May event suggest an average earthquake recurrence interval of about 2,000-10,000 years.
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Geological Society of America