Magnetic survey off the west coast of North America, 32 degrees N. latitude to 42 degrees N. latitude

A ship-towed magnetometer survey of an area 2,300 mi. wide off the foot of the continental slope along the coast of California has revealed a narrow pattern of anomalies of about 400 gammas magnitude trending N.-S. for more than 500 mi. The pattern is interrupted at the known faults and elsewhere; offset of the pattern at the Murray fault suggests a right-lateral displacement of about 84 nautical mi. The anomalies are such as might be expected of slablike structures underlying the ocean floor; geological possibilities include basic lava flows, topography of the main crustal layer, and intrusion of ultrabasic material from the mantle.