Oregon State University sea gravity investigations

Abstract

In 1963 Oregon State University obtained over 4,000 miles of continuous gravity measurements at sea from the Oregon coast westward to beyond the seaward extension of the San Andreas fault and from Point Mendocino, California, to Astoria Canyon, Oregon. Measurements were made on the U. S. Coast Guard cutter Yocona, a 213‐foot, 1900‐ton ship. The measurements include 7 lines from the coast westward for a distance of 100–300 miles, 15 profiles across the San Andreas fault extension, and 1 profile across the Mendocino escarpment. Free air anomalies for these measurements have been calculated, and a free air anomaly map has been contoured.The reliability and accuracy of LaCoste‐Romberg gravity meter S‐9 was checked against a gravity range which had been previously obtained from an underwater gravity meter off Newport, Oregon. Surface‐ship gravity readings were found to be accurate within 6 mgal, even at Browne corrections up to 450 mgal, where the errors included navigational effects. Comparable errors were obtained at intersections of profiles in the larger gravity program off Oregon. Results of the reliability determinations of meter S‐9 are being prepared for publication, as based on measurements over the Newport gravity range, on measurements past an offshore petroleum platform in the Gulf of Mexico, and from intersections of numerous gravity profiles in the Gulf of Mexico and off the coast of Oregon.