[ScottfromNJ]

Wonder if all that heavy rain California’s had causes erosion in these faults and actually increases the earthquake risk?

[Zathras]

Geologic history for CA says to see an increase in activity 10-24 months AFTER a large rain season.
The theory says that it takes that long for the water to reach the fault depth and thus act as a lubricant.

This is one of the primary reasons LA has opposed re-flooding the Salton Sea from the Gulf of CA.
Analysis indicated it would cause increased quakes in So-Cal.

[JimRed]

Wonder if all that heavy rain California’s had causes erosion in these faults and actually increases the earthquake risk?

I don't click on USA Today, but let me make a semi-educated guess (High honors in a geology course at community college in 1972): Faults like that are sometimes miles deep in the lithosphere (crust) and the water penetration would take years at least to affect it, so no.

[polymuser]

Wonder if all that heavy rain California’s had causes erosion in these faults and actually increases the earthquake risk?

I'd say soil liquefaction would increase significantly from an earthquake. Instant quicksand all over.

[Viking2002]

I've heard that excess rainwater/snowmelt can actually migrate into crustal fissures, and 'lubricate' them, making the plates easier to slip.