http://temblor.net/earthquake-insights/m5-3-earthquake-strikes-offshore-southern-california-6741/
Geophysicist Mark Legg commented, “About every six years there’s been a M5+ offshore southern California. There was a M=6.0 in 1981 nearby. In this intersection area, which marks the boundary between the inner and outer continental borderland, there are many faults. The Santa Cruz Basin itself was ripped from Baja California and shoved northwest by the San Andreas shear zone. The Basin is ramming into the Transverse Ranges, marked by the Santa Cruz and Santa Rosa Islands, which have been caught in the shear zone and spun like ball bearings.
Thanks PP I knew someone would have data on it!
So it is normal. Thanks