San Andreas set for 'big one'

New earthquake research has confirmed the southern end of the San Andreas Fault near Los Angeles is overdue for the ‘big one’

After three centuries the San Andreas fault is set for the 'big one'

The lower section of the fault has not produced a major earthquake in more than three centuries. The new study, which analysed 20 years of data and is considered one of the most detailed analyses yet, found that stress has been building up since then, and that the fault could rupture at any moment.

According to Yuri Fialko of the Scripps Institution of Oceanography at the University of California, who carried out the study: “The southern section of the fault is fully loaded for the next big event.”

Although seismologists have not been able to predict when a great earthquake will occur on the southern San Andreas, most believe such an event is inevitable. Fialko says he has produced the clearest evidence to date of the strain build-up that will ultimately result in a large earthquake along the southern San Andreas Fault.

“The data suggest that the fault is ready for the next big earthquake but exactly when the triggering will happen and when the earthquake will occur we cannot tell. It could be tomorrow or it could be 10 years or more from now,” said Fialko.

Using satellite radar and global positioning data, Fialko measured the movement of the southern San Andreas between 1985 and 2005. Small movements along a fault can relieve strain and calculating those subtle motions allows geologists to figure out how much strain is building up.

The analysis appears in the latest issue of Nature.