Kevin,
The California Earthquake Certification is offered through Vale National. They have locations in Fresno, CA, Arlington, TX, and Harrisburg, PA. The certification allows you to work on claims made on policies issued by the California Earthquake Authority, and is valid for three years. These policies are written by most of the major HO market players in California. I believe both the California Earthquake Authority and Vale National have websites you can visit in order to find out more. Vale requires that you be sponsored in order to attend. If you are associated with a CAT vendor, I would recommend that you contact them and tell them you want to take the earthquake certification course. If they say, "Huh, what's that?", contact David Morse Associates, Worley, Crawford, Pilot or some other vendor who has an interest in earthquake CATs and see if they will sponsor you to attend the training.
In terms of self training, you would do well to learn all you can about concrete construction. Earthquake CATs present some unique challenges, as Ray Hall pointed out. One of the challenges that may well drive a catadjuster crazy is that the files are not quick closers, once and done. An earthquake is not really a single event. The aftershocks can be nearly as devastating as the original event. This may mean the file keeps reopening and you keep returning to the same loss to write supplemental damage. It also means you are at ground zero when the ground decides to shake once more. That can be unnerving for the adjuster as well as the insured.
After the Northridge Earthquake, the State of California decided that all aftershocks within 6 months constituted part of the same earthquake. This was easier than trying to determine which aftershock caused what damage, but meant the price tag kept going up. Most, if not all, independents were on a day rate and many were here for more than 1.5 years.
It can be a very lucrative type of CAT, but is not really for those who don't know what they are doing or those who want to get back to Texas after a month. The legal climate of California will present challenges that one may not encounter in the heartland. When I went independent in 1998, they were still reinspecting many of the earthquake losses from 1994 in an attempt to finish them up.