Seasonal deformation of 2-mile straight line

Relative motions of parts of the Stanford Linear Accelerator housing were measured and corrected repeatedly between 1966 and 1971. The vertical motion shows a steady decline with time, whereas both vertical and horizontal motions have a periodic component of one cycle per year. Displacement is upward in winter and downward in summer, and is clearly correlated with rainfall and water level in nearby wells. Consequently, the observed displacements must be associated with local soil and rock properties, and are not due to tectonic stress around San Andreas fault system.