Pacific Coastal & Marine Science Center
Coastal and Marine Earthquake Studies
|Central California/San Francisco Bay Earthquake Hazards Project, 1998
The Pacific and North American Plates
The Pacific-North American plate boundary has evolved over time. Before 30 million years ago, the entire west coast of California was a subduction zone (where one plate is forced under another), resembling the present-day Oregon-Washington coast line. Since 30 million years ago, the San Andreas fault has been cutting its way northward through the California coastal margin.
From Bohannon, R.G., and Parsons, T., 1995, Tectonic implications of post-30 Ma Pacific and North American relative plate motions: Geological Society of America Bulletin, 107, p. 937-959