Lets continue northward along the west coast now, continuing to try and understand how an acceleration of change in the nature of plate-tectonic activity implied by the Edgar Cayce readings relates to the statement that "Los Angeles, San Francisco, most all of these will be among those that will be destroyed."
Consider Cape Mendocino, California, for example, where three tectonic plates come together in a "triple junction"; the plates in question are the Pacific, Gorda, and North American plates. Some of the highest rates of crustal deformation, surface uplift, and seismic activity in North America occur at this Mendocino triple junction. On April 25-26, 1992, for example, three powerful quakes occurred here, along with 1.4 miles of coastal emergence. According to the U.S. Geological Survey, the main shock of the series "may be the forerunner of a much more powerful, tsunami-generating earthquake in the Pacific Northwest...such an event could cause (great) damage due to the ground shaking, and the associated tsunami could devastate the coasts of California, Oregon, Washington, and British Columbia."
In early 1996 scientists detected a major volcanic upheaval at the north end of the sea-floor rift segment known as the Gorda Ridge. This is testimony to the ongoing geologic outpouring of material from the Earth's interior in this subsea region of the Pacific Northwest as heat is transported to the surface in the vicinity of the Gorda Ridge.