Using satellite radar data and GPS measurements, Chinese researchers have explained the exceptional geological events leading to the 2008 Wenchuan Earthquake that killed nearly 90 000 people in China's Sichuan Province.
"One of the very fundamental issues for understanding an earthquake is to know how the rupture is distributed on the fault plane, which is directly related to the amount of ground shaking and the damage it could cause at the surface," said Dr Jianbao Sun of the Institute of Geology, China Earthquake Administration (IGCEA).
To learn this, Sun and Prof. Zhengkang Shen of IGCEA and Peking University's Department of Geophysics, and collaborators acquired two kinds of satellite radar data: Advanced Synthetic Aperture Radar (ASAR) data in C-band from ESA's Envisat satellite and Phased Array type L-band Synthetic Aperture Radar (PALSAR) data from Japan's ALOS satellite.
Applying a technique called SAR Interferometry (InSAR) on the data, the researchers produced a set of 'interferogram' images covering the entire coseismic rupture region and its vicinity. This interferometric map revealed the amount and scope of surface deformation produced by the earthquake.
"This is perhaps the very first time people have seen the complete deformation field produced by an earthquake on such a large scale," Sun said.
InSAR involves combining two or more radar images of the same ground location in such a way that very precise measurements down to a scale of a few centimetres can be made of any ground motion taking place between image acquisitions. Coloured interferograms usually appear as rainbow fringe patterns.
The researchers combined these SAR satellite data with GPS measurements and developed a model that shows fault geometry and rupture distribution of the Longmen Shan fault zone, a series of parallel faults that run for about 400 km from southwest to northeast in the region. The earthquake that struck on 12
|Contact: Mariangela D'Acunto|
European Space Agency