Hi Glen. There has been an ongoing debate about the Delta Levees for a number of years now. They are at risk, but no one has an answer as to how much. The Rodgers Creek fault could cause a levee break, but there are faults much closer the delta that could also cause breaks at lower levels of shaking.

The one fault that always bothers me is the Great Valley Thrust Fault. There have been 3 quakes that could be associated with this fault. They would be the Vacaville/Winters quakes of 1892 and the Coalinga quake in 1983. Take Care…Don in creepy town

A generic Coast Range-Sierra Block (CRSB) fault model has been assumed in previous and current evaluations of probabilistic ground motions in the Delta, but no positive evidence for the presence of blind thrust faults similar in style and rate of activity to those in Coalinga-Kettleman Hills region has yet been documented in the Delta. A systematic evaluation of the CRSB is needed to assess whether the structure is present in the Delta region. Because the presence of the CRSB would lead to predictions of a higher density of levee failures, additional work to evaluate evidence for and against the CRSB model is critical to reduce uncertainty about the likelihood of a catastrophic levee failure due to large, infrequent earthquakes.

There is significant uncertainty about the orientation and sense of slip on the Pittsburg-Kirby Hills fault zone (PKHFZ), which is the source of persistent background seismicity in the western part of the Delta near Pittsburg. The PKHFZ has been the focus of several USGS studies (BASIX-I,II,III) and represents the easternmost strike-slip fault in the San Andreas fault system.

http://www.msa.saccounty.net/waterresources/files/DMA/Section%206-7%20ISLETON-DELTA%20element%203rd%20FINAL.pdf

• Delta Quake Hazards