Earthquake Research Institute, Univ. of Tokyo Report on The 2008 Sichuan Earthquake

[Update 2008.05.16]

---

The following is a flash for the Sichuan earthquake occurred on May 12, 14:28 (local time). Details may be revised when additional data are obtained. We also updated the finite fault model. (ERI Source Process)

• The epicenter (indicated by the red star in the figure bellow) may be located on Longmenshan fault (yellow line). (The figure is adapted from He and Tsukuda, 2003 (PDF) )

• The Longmenshan thrust zone mainly consists of three thrusts and associated fault-propatation folds, thrusting southeastward over the Sichuan rigid massif. This zone is approximately 60 km wide, and constitutes the topographic boundary between the eastern Tibetan Plateau and the Sichuan basin. The total vertical slip rate is about 1-2 mm/yr, and thus the convergence rate across the thrust zone is inferred to be 4-6 mm/yr.

• The northward indentation of the Indian plate into the Tibetan crust after the collision between the Indian and Eurasian plates induced uplift and deformation of the Tibetan Plateau. The continental crust of China, thus, is highly active tectonic area.

• This continuing northward indentation resulted in three types of tectonic deformation: convergence zones surrounding the plateau, strike-slip fault zones associated with the laterally extruding crustal blocks in the eastern plateau (i.e. Kunlun earthquake in 2001 [M8.0, Lin, A., M. Kikuchi, and B. Fu, "Rupture segmentation and process of the 2001 Ms 8.1 Central Kunlun earthquake, China", Bull. Seismo. Soc. Am., 93, 2477-2492, 2003, Lin et al. "Co-seismic strike-slip and rupture length produced by the 2001 Ms 8.1 Central Kunlun earthquake", Science, 296, 2015-2017, 2002.]), and extensional basins in the southern plateau on which the Longmenshan fault is located.

• The historical earthquakes aroud this fault include two M 7.2 earthquakes occurred on August 16 and 25, 1976. These earthquakes have been claimed to be predicted, based on various phenomena.

• A M 7.5 earthquake occurred on August 25, 1933, about 50 km north of the 2008 event. This earthquake caused about 6,800 victims, and created four earthquake lakes, by damming up a river. Forty five days later, this dam was broken and the flood caused another 2,500 victims.

Adapted from He and Tsukuda, 2003

---

ERI Source Process [2008.5.16] Updated!

---

Links

• USGS

Copyright 2008 ERI. All rights reserved.