WESTERN U.S. PLATE BOUNDARY ZONE

ALTHOUGH MOST (ABOUT 75%) OF THE MOTION BETWEEN PACIFIC AND NORTH AMERICAN PLATES OCCURS ON THE SAN ANDREAS, THE REST IS SPREAD OVER A BROAD ZONE OF EARTHQUAKES (DOTS), FAULTING, AND HIGH TOPOGRAPHY EXTENDING AS FAR EAST AS UTAH

THAT INCLUDES THE ZONE OF EXTENSION IN THE BASIN AND RANGE

(Bennett et al, 1999)

ARROWS: GPS & VLBI SITE MOTION VECTORS WITH RESPECT TO NORTH AMERICA