The effect on business is likely to be negligible, if any. Most people who don't live or didn't grow up in the area don't realize how much thought goes into earthquake safety when building new structures or retrofitting older ones. Almost everything is built to withstand extremely powerful earthquakes.
Obviously, there would be some damage to roads and buildings (particularly older structures), and likely some loss of life. However, the fantastical "San Andreas" movie scenario or "California falling off into the ocean" meme simply cannot occur here. Our faults aren't actually even capable of a 9.0 magnitude earthquake (The San Andreas fault would max out at about an 8.2). We have about a 7% chance of seeing an 8.0 in the next 30 years. If it happens, we'll be fine. Most of people's fears of California earthquakes are based on historical knowledge of early 20th Century earthquakes and the damage they caused. It's important to put it in perspective- those structures were largely thrown up in haste during the Gold Rush, with minimal to no oversight. Comparatively, the 1989 earthquake was barely a blip after a century of learning to handle this stuff.
However, if you could send us some water, that'd be great.