This action is for continued support of a field experiment designed to investigate the performance of buried pipelines when subjected to the ground shaking induced by a large earthquake; specifically the lateral offsets and ground strains induced by seismic wave propagation. This experiment has been constructed at Owens' Pasture, near Parkfield, California. This site was chosen so as to capitalize on the predicted recurrence of the 1966 Parkfield-Cholame earthquake sequence on the San Andreas fault. Although this earthquake has not yet occurred, transient and residual strains in the instrumented pipe segments were measured during the October 17, 1989 Loma Prieta earthquake. The distribution of strains in the pipes and their correlation with ground movements yields important insights into the behavior of girth-welded steel pipelines of the type used for oil, gas and water transmission. Data from the Loma Prieta earthquake and from the main Parkfield event yet to occur make it possible to evaluate critical assumptions of analytical models and, if necessary, revise them. One objective of this experiment is to evaluate current analytical models in light of the low amplitude data collected at Parkfield during the Loma Prieta earthquake. The measurements made during this earthquake indicate that when the predicted earthquake at Parkfield occurs, valuable data will be obtained from this event. This leads to the second goal, which is to maintain the experiment through 1993 in anticipation of this predicted event occurring. This is but one of many experiments at Parkfield, supported by federal and state agencies and non-profit institutions, which were installed and are being maintained in anticipation of the predicted earthquake occurring.
