I just finished 2 full days of work reviewing a 200 page manuscript by someone who rejects strike-slip motion in a part of California where there has been 500 km of right-lateral. It made me cranky. So, I'll creep you guys out by talking about a quake that could make LA Basin shake for minutes....the 1857 quake on the San Andreas fault ruptured a couple of hundred km. For argument, let;s call it 200 km...it was probably more. If the rupture velocity is 5 km/s, it would take 40 s just to break. If a quake like that were to start near San Bernadino and rupture away from you, then it would take longer for the waves from the far end of the fault to get to you than the near end.....might take 40 s longer...so, the waves entering LA Basin would be entering for 1 min 20 s. After which, they would bounce around, amplify, etc. At least the energy would not be directed at you...it would be more spread out...less amplitude.

The 1964 Alaska earthquake lasted about 4 minutes. 1960 Chile must have lasted longer. But, the ruptures of those were so long (600 km and 1000 km) that you might not feel the shaking from the far end...
Chris