Analysis of repeated leveling observations in the vicinity of the San Gabriel fault in Southern California indicate subsidence immediately south of the fault relative to points to the north, south, and east. These observations were previously interpreted as reflecting tectonic motions associated with either the ''Palmdale Bulge'' or with preseismic effects of the San Fernando earthquake. Relative subsidence between 1953 and 1964 reaches approximately 9 cm and extends over a distance of more than 20 km. Subsidence occurs directly above the Sangus aquifer and shows a temporal correlation with the history of water level decline within the aquifer. The degree of subsidence of individual benchmarks is roughly proportional to the product of aquifer thickness and water level decline at the location of the benchmarks. These observations strongly suggest that movements of the surface near the San Gabriel Fault, previously inferred to be of tectonic origin, actually result from near surface sediment compaction within the Saugus basin.