Smithsonian Magazine: "What Will Really Happen When San Andreas Unleashes the Big One?"

Not as much detail as I would like, but the article makes a few good points and has some links to other sources of information. The article states:

To figure out what could realistically happen when the Big One finally strikes, a team of earthquake experts sat down sat down several years ago and created the ShakeOut scenario. Seismologists modeled how the ground would shake and then other experts, including engineers and social scientists, used that information to estimate the resulting damage and impacts. The detailed report examines the effects of a hypothetical 7.8 quake that strikes the Coachella Valley at 10 a.m. on November 13, 2008. In the following minutes, the earthquake waves travel across California, leveling older buildings, disrupting roads and severing electric, telephone and water lines.

But the quake is only the beginning.

Hundreds of fires start, and with roads blocked and the water system damaged, emergency personnel aren’t be able to put them all out. Smaller fires merge into larger ones, taking out whole sections of Los Angeles. The lines that bring water, electricity and gas to Los Angeles all cross the San Andreas fault—they break during the quake and won’t be fixed for months. Though most modern buildings survive the shaking, many are rendered structurally unusable. Aftershocks shake the state in the following days, continuing the destruction.

The scenario is actually somewhat of an underestimate, notes one scientist behind the ShakeOut, USGS seismologist Lucy Jones. The report’s team was surprised by the extent of the fire damage from the quake, Jones says, but it could be worse if the Santa Ana winds are blowing when the event happens. These seasonal winds blow dusty, dry air from inland toward the coast, increasing risks of wildfires. And while Los Angeles keeps a supply of water on its side of the San Andreas, the reservoirs have been drained by the current drought—if the quake struck today, water reserves wouldn't last the maximum of six months that they would when full, she notes.

Overall, such a quake would cause some $200 billion in damage, 50,000 injuries and 2,000 deaths, the researchers estimated. But “it’s not so much about dying in the earthquake. It’s about being miserable after the earthquake and people giving up on Southern California,” says Jones. Everything a city relies on to function—water, electricity, sewage systems, telecommunications, roads—would be damaged and possibly not repaired for more than a year. Without functioning infrastructure, the local economy could easily collapse, and people would abandon Los Angeles.