I am not quite as pessimistic as you about the aftermath of a major quake in LA. Theregion has experienced Northridge in 94 and Sylmar in the early 70s, both with major damage. I believe there was indeed some looting, but nothing like societal collapse.

During the Northridge event, a lady thought the shuddering she felt while driving on the freeway might have been a flat tire. She was relieved to find it was "only" an EQ. It makes sense for her personally when you think about it. Changing a tire during the morning rush hour on a major freeway is fraught with peril