Continental Drift by James D. Houston
The San Andreas Fault is both a real and a metaphorical player in this novel of northern California in the early 70s. Set on a ranch near Monterey Bay, it explores relationships in a family jarred by the return of a son from Vietnam, almost whole but shaken and confused. His return coincides with a series of bizarre killings that panic the community--a reminder that in the legendary land of promise abundant possibilities and agents of destruction live side by side.