Born and raised in LA here; currently live in the San Fernando valley which is close to the most dangerous faults. I'm almost 36. Here are my thoughts...
I've been through both the '87 Whittier and '94 "Northridge" (Reseda) quakes. They, especially the '94 quake, were devastating. Highway 14 that links the Lancaster/Palmdale area where Edwards Airforce Base to Los Angeles fell down by the 5 (for the second time; the first was during the Sylmar quake of '71). That said, we're used to it. Too used to it.
Most people don't even remember the VERY large June '92 quake out by somewhere called Joshua Tree because it was only a 6.x magnitude event. I point that out because I think outside of businesses that are in high rises mandated by city municipal codes to have fire-code compliant emergency plans and supplies, the average strip mall business or private residence is likely under-supplied and the resident under-prepared. I oughta know because for years I was one of them.
It's sad I know. But if you thought Hurricane Katrina looked like Hell on Earth on CNN, just wait 'til you get the BARELY stable city of Los Angeles look like it was hit by a daisy cutter after an 8.x levels half the town. No running water for days, undriveable roads due to glass blown out of buildings everywhere. Fire departments won't be able to reach all the fires from the gas mains that will have ruptured and exploded.
ONE town here that looks very prepared is Burbank. There are multiple gun stores here, amateur radio stores (one's next door to the other on one road), emergency supplies. And they're in business because they sell a lot of supplies all the time. So I have no doubt they will be able to survive The Big One, and be able to protect themselves in case the looters are feeling opportunistic.
The City on the other hand, I'm not so sure. LAPD will declare a city wide tactical alert pretty much immediately, gas stations will be shut down (because there will be no electricity to power the gasoline pumps, ATM machines and credit card terminals). It won't be good times.
One problem is, supplies are expensive. Good guns aren't cheap. Ammo isn't cheap. Training isn't cheap. Emergency food, emergency power, etc. Aren't cheap. Back when I was overworked and underpaid, I was dealing with shady roommates 'cause I could hardly make ends meet. That did change but I was slow to see the light. Even after a big 5.6 quake hit close to downtown L.A. while I was at work. Our first really large one in years.
Or the big Studio City 4.6 quake that made this guy news anchor on KTLA Internet famous because of his "we're having an earthquake" panic on live TV. ;-) Anyway, what really finally made me realize I need to get ready, and get supplies (as well as a way to defend it and ourselves in case there's looting, riots, etc) was what happened last year...
There was a Swarm of upper-strength 3.x earthquakes that struck the O.C. for several Days. The news here always overreacts when there is a quake. 2.9 makes someone's lawn chair tip over and all local stations will spend hours covering it... They'll drag Dr. Lucy from CalTech out of bed at 4 in the morning if they have to tell people what's going on, etc. It's kind of embarrassing. This isn't Japan where they have "the big one" almost every other year (who's worried about a 7.x when you can have a freaking 9.x). But this was legitimately scary. Even for a SoCal native like me.
So I got my act together and stocked up on water, a way to deal with hygene and going #2 when there's no running water, canned heat and 25-year shelf-life MREs so we're good for up to two weeks. I own a SD40VE and an SD9VE (so we don't just have one while my wife gets ready to own one of her own).
After I spent the money and sometimes even now, I think I spend a lot of time and whole lot of money on this stuff. It's a nice part of town where we live and no disasters (man made or natural) yet. But sometimes I see an air unit set up over a parameter nearby and think, what if their suspect runs through the backyards and tries to hide out in my house? Sometimes I see shady characters that make me think, I sure am glad I can handle it if this person was actually casing my home and figures they can take me. Terrorists targeting apartments isn't too far from my mind and if there's a riot, I don't want to just Hope they stay away from me. They might (they did the last time), but what were we gonna do if they didn't?
I feel like I've spent years just getting lucky, with quakes or with crime. And I figure God's only going to give me so many chances figure out that I need to take care of business and pay attention to my responsibility to make sure my wife and I survive a SHTF moment.