A California earthquake forecast, the 2008 Uniform California Earthquake Rupture
Forecast, Version 2 (UCERF 2), has been prepared by the Working Group on California Earthquake Probabilities (WGCEP).
Of the hundreds of seismogenic (earthquake causing) geologic faults in California UCERF classifies only six faults as Type A sources, meaning there is sufficient information to both estimate and model the probability of a Magnitude (M) 6.7 or greater earthquake within 30 years.
These six faults (summarized in Table A, below) are the: (1) San Andreas (split into northern and southern sections, (2) San Jacinto, (3) Elsinore, (4) Garlock, (5) Calaveras, and (6) Hayward-Rodgers Creek.
Faults which are known to be slipping (and therefore seismogenic) but lack sufficient information to fully model how close they might be to rupture are classified as Type B. About twenty of these faults (see Table B) are estimated to have a 5% or greater chance of an M ≥ 6.7 earthquake within 30 years. An additional six areas where strain is accumulating but where knowledge is insufficient to apportion slip onto specific faults are classified as Type C sources.
There is additional chance of earthquakes on faults that were not modeled, and of lesser earthquakes. Northern California has an estimated 12% chance of an M ≥ 8 megathrust earthquake on the Cascadia subduction zone.
UCERF has also prepared "participation probability maps" of the chance that any area will experience an earthquake above a certain magnitude from any source in the next 30 years (see figure).
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