Construction standards are very good in US earthquake prone areas.
It would take a much stronger one to get major damage. Not sure what that number is.
1989 Loma Prieta was 7.0 and killed 63 people in San Francisco area.
Yes did a fair amount of damage; things are probably in better shape now
Its still dangerous due to are areas of landfill. They also really did not enforce building codes till rather recently.