Sichuan Province primed for more earthquakes after May quake

30 December 2008 by Tom Marshall

The deadly earthquake that struck China in Spring 2008 has activated neighbouring earthquake fault-lines, according to new research. These faults are now more likely to fail, leading to smaller, but potentially more deadly earthquakes.

Workers rebuilding the road

Clearing up after the Sichuan earthquake

The magnitude eight earthquake shook the densely populated Sichuan Province on 12 May killing an estimated 69,000 people and leaving around five million people homeless. Buildings that stood directly on the rupture were shaken to their foundations, collapsing instantly.

Scientists are aware that other faults exist in this region of China, but they still know very little about where they are, what their past earthquake history is and how they might behave in the future.

"The fault zone in Sichuan Province is relatively young and it hasn't yet settled on a stable configuration, which make future events harder to forecast and plan for," said Alex Densmore, who led the research. Densmore is deputy director of hazard research at the Institute of Hazard and Risk Research in the Department of Geography at Durham University.

In general, the earthquake occurred along faults we knew were active, so in that sense it was foreseeable, but not predictable.

- Dr Alex Densmore, Durham University

Densmore was the first UK scientist to visit Sichuan Province to analyse the earthquake zone soon after the May earthquake hit. He worked alongside colleagues from the Chengdu University of Technology, the Seismological Bureau of Sichuan Province and Shell UK. He presented the team's findings at the American Geophysical Union Fall Meeting in San Francisco in mid-December.

The researchers painstakingly mapped the location, orientation and scale of surface slips in four key places where the earthquake struck. They also used satellite imagery as well as Chinese aerial photographs and overlaid these on existing fault maps of the area.

"In general, the earthquake occurred along faults we knew were active, so in that sense it was foreseeable, but not predictable," said Densmore.

No evidence of recent activity

The team compared surface ruptures with evidence of long-term deformation on both mapped and unmapped faults to see which regions had been active in the past. The earthquake appears to have reactivated nearby faults in Sichuan that have shown no previous evidence of having been active recently.

Reconstruction efforts are picking up pace and Densmore says that Chinese officials would be well advised to prevent building directly on top of active faults. "If they consider imposing buffer zones around faults, they could save a lot of lives in the future," Densmore explained.

The Sichuan earthquake occurred along two known fault, the Beichuan and Pengguan faults, which run along the eastern margin of the Tibetan Plateau. Its epicentre was around 92 kilometres north-west of Sichuan's capital city, Chengdu.