Satelite data reveal Calaveras fault's creep

Satellite data of the last to decades, helped in mapping the land creep along the Calaveras and the Hayward faults east of the San Fransisco Bay, enabling scientists to reconstruct the underground geometry of the fault complex and estimate the magnitude of future earthquakes.

30 ground-based instruments installed along Hayward and nine along Calaveras faults have provided scientists with data on the creep of land along the two fault components of the San Andreas fault system. To get a better estimate of the creep, Estelle Chaussard, a postdoctoral fellow in earth and planetary science at the University of California, Berkeley and her colleagues, used 19 years of satellite measurements processed with a special technique to better analyze the Hayward and Calaveras complex.

The scientific team used the interferometric synthetic aperture radar technique (InSAR) upon satellite images to derive creep measurements along the two faults. Based on these measurements, they found out that areas of the Calaveras fault move as much as 0.47 inches per year (12mm) and other parts remain still. Additionally to the Calaveras creep found with InSAR, creep movements were also discovered to be taking place more than 9.3 miles (15 kilometers) farther south along the Hayward fault than what was previously thought. It also turned out that in case a slip occurs along the specific fault, could lead to a magnitude 7.1 earthquake, much stronger than what was initially thought.  

Based on the specific data and measurements of small periodic earthquakes, it became possible to model the underground structure of the fault system, providing evidence on the long suspected interconnnection between the two faults. Given the specific finding, scientists were able to re-evaluate the energy stored in the fault system