Chinese quake can help evaluate similar fault areas for seismic risk

Washington, July 22 : Geologists from Penn State and Arizona State University in the US have suggested that topographic analysis of the Sichuan area in China, which witnessed a massive earthquake on May 12 this year, can help evaluate other, similar fault areas for seismic risk.

Analysis of the Sichuan area has now shown that topographic characteristics of the highly mountainous area identified the mountain range as active and could have pointed to the earthquake hazard.

The researchers note that "the landscape itself encodes information about the rates and patterns of tectonic activity."

According to Eric Kirby, associate professor of geosciences, Penn State, the ability to read these erosional landscapes is now good enough that researchers can use topographic analysis as a reconnaissance tool to identify areas of active rock uplift.

In remote mountainous areas, this approach can shed light on the activity of blind and hidden faults.

Kirby, working with Kelin Whipple, professor, School of Earth and Space Exploration, Arizona State University, and Nathan Harkins, graduate student, geosciences, Penn State, used topographic analysis of the area of the Sichuan earthquake to suggest a way to refine existing maps of earthquake risk in other places.

Previous studies using data from Global Positioning System satellites found the area had slow deformation rates that indicate modest strain and seismic hazard, but this description contradicts the impression given by the rugged mountains.

Similar terrain in the Himalaya Mountains is associated with rapid convergence - tectonic plates moving toward each other.

Previously, Kirby and Whipple, focusing on geomorphic analysis, suggested that faults in the Sichuan region were active and were associated with regions of ongoing uplift of the mountains.

"The 2008 earthquake struck on one of the faults identified with high rates of rock uplift," said Kirby. "Topographic analysis can have potentially important implications for anticipating the likely locations of events in this area," he added.

According to the researchers, topography can indicate deformation of the crust at depth, even when short-term satellite measurements do not.

"Where shortening rates are slow and satellite data may be ambiguous, topographic analysis can help guide the identification of potential earthquake risk," said Kirby.

The researchers looked at such things as anomalously steep river channel profiles extracted from digital elevation models, digital maps that represent changes in elevation of the land.

They noted that these methods were tested in areas where the actual tectonic activity levels were already known and that the Sichuan earthquake presents an ideal laboratory to further check the approach.

ANI