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Interesting abstract from last year. Entire paper available here:

http://www.geology.cwu.edu/index.html?page=http%3A//www.geology.cwu.edu/facstaff/charlier/currentprojects/saf_carrizo.html

Variations of fault slip per event on the Carrizo Segment, San Andreas Fault...about 95% of displacement at the Carrizo Plain on the San Andreas fault northwest of Los Angeles occurs in big earthquakes. Excavations across the fault allow to collect for information about earthquakes of the past couple of millennia. We found that most of the motion along this stretch of the San Andreas fault occurs during rare but large earthquakes.
Of the six offsets discovered in the excavations, three and perhaps four were offsets of 7.5 to 8m, similar in size to the offset during the great earthquake of 1857. The third and fourth events, however, displacement was only 1.4 and 5.2m. Offsets of several meters are common when the rupture length is very long and the earthquake is very large. For example, the earthquake of 1857 had a rupture length of about 360 kilometers (225 miles), extending from near Parkfield to Cajon Pass. So, the five events that created offsets measuring between 5.2 and 8m likely represent earthquakes that had very long ruptures and magnitudes ranging from 7.5 to 8m. Taken together, these five major ruptures of this portion of the San Andreas fault account for 95% of all the displacement that occurred there over the past thousand years or so.
The practical significance of the study is that earthquakes along the San Andreas, though infrequent, tend to be very large. Years ago, paleoseismic research showed that along the section of the fault nearest Los Angeles the average period between large earthquakes is just 130 years. Ominously, 147 years have already passed since the latest large rupture, in 1857.

The term overdue gets thrown around a bit too much; there are a few cases where it does apply, though, such as the southern San Andreas.

Another place where it applies is Utah; a lot of paleoseismoligical digging has been going on and along almost the whole Wasatch front the recurrence pattern of quakes indicates the next big quake there should be about...now.

offsets of 7.5 to 8m, similar in size to the offset during the great earthquake of 1857

It is hard to imagine the plates being displaced by 26 feet in a single event along the fault. The energy for that must be tremendous.

Fortunately there wasn't a lot of development in southern California in 1857. Come 2007 (or whenever) the damage and loss of life will be staggering...