The European Space Agency (ESA) teamed with China in a joint program to understand the seismic cycles in the Asian country using satellite radar data to monitor ground deformation across major continental faults in China.
Dragon 2 Programme (the name of the joint research team) will implement Synthetic Aperture Radar (SAR) satellite data and a technique known as SAR Interferometry (InSAR), along with GPS data, to measure the ground deformation that occurred during the Wenchuan earthquake that struck China’s Sichuan Province last May.
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 centimeters or even millimeters – can be made of any ground motion taking place between image acquisitions.
This tecnique has allowed Dr Sun Jianbao of the Institute of Geology, China Earthquake Administration (IGCEA), Prof. Shen Zhengkang of IGCEA and Peking University, and collaborators including Dr Cecile Lasserre from France’s Laboratoire de Geophysique to generate ‘interferogram’ images, which appear as rainbow-colored fringe patterns, showing the ground displacement that occurred during and after the earthquake.
The Wenchuan earthquake occurred on the Longmen Shan fault, along the eastern margin of the Tibetan Plateau. Following major earthquakes, changes in stress along the faults in the region can lead to subsequent earthquakes. Using InSAR and GPS data, scientists are able to measure and monitor where and how this stress changes as well as how any associated deformation is distributed.
If the area is moving slowly after the quake, then it is not accumulating energy. If, however, one area on the fault is not slipping but there is creeping movement around it, then scientists know they have to watch it more carefully.