Southern California's last great earthquake and clues about the next one

This year marked the 125th anniversary of the great Fort Tejon, California, earthquake of January 9. 1857.  By digging large trench along the segment of the San Andreas fault that broke near Pallett Creek and by studying contemporary records, Kerry Sieh of the California Institute of Technology has found evidence that the fault needs, on average, at least 125 years to prepare for its next catastrophic failure.  Te remainder of this wait, of course, could be anywhere this century or the next.