Geodetic and geophysical crustal anomalies in southern California came in for a lot of attention at the 1978 Fall Meeting. In a paper titled ‘Regional Elevation and Gravity Changes in the Palmdale Bulge Area,’ John D. Bossier of the National Geodetic Survey reported on the Survey's efforts to relevel nearly 5000 kilometers of southern California because of the anomalous vertical crustal deformation. The magnitude of the current leveling effort is without parallel in the United States in the distances involved in such a short time frame.
From roughly 1930 to 1978, repeat surveys of southern California were done to redefine the relative locations of points on the earth's surface following earthquakes such as those in Long Beach (1932), Kern County (1952), and Sylmar (1971). This work, however, revealed a crustal uplift known as the Palmdale Uplift that was eventually followed by an episode of rapid subsidence, amounting in most cases to half the original uplift amplitude.