Southern California uplift—Is it or isn't it?*



The Southern California session of the fall 1980 John Muir Geophysical Society meeting was an attempt to answer the question of whether the Southern California Uplift was real tectonic deformation or merely an artifact of systematic survey errors. The three principal speakers were D. D. Jackson (UCLA), W. E. Strange (National Geodetic Survey), and R. Stein (Lamont-Doherty—formerly with the U.S. Geological Survey). Jackson and Strange were arguing the negative side, i.e., that the uplift did not exist, while Stein argued that the uplift was real.

In leveling, observations are made so as to determine the height of permanent benchmarks, typically a kilometer or so apart relative to each other. Attempts are made to locate the marks on competent rock, although it is sometimes the case that marks are in fact placed in unconsolidated alluvium or in other soft ground, leading to unwanted instability. Additionally, real displacements are sometimes seen in alluvia that derive from nontectonic causes, such as water withdrawal.