A large number of excellent strong ground motion and structural response accelerograms were recorded during the M 7.5 Landers earthquake of June 28, 1992, which was the largest to occur in California since 1952. There was relatively little damage to engineered structures due to the remote location of the epicenter. However the ground motion records obtained from this event are among the most significant measured to date, and especially the recording from a free-field instrument installed and maintained by the Southern California Edison Co. (SCE). This instrument was located in Lucerne Valley within approximately one mile of the surface rupture, thus providing one of the closest near- field recordings of a major U.S. earthquake. A preliminary analysis of this record shows a very pronounced long-period pulse in the displacement with an amplitude of about 120 cm. This type of ground motion could have a serious effect on the response of large structures. The existence of significant long-period motion in the near-field of a large earthquake has been postulated for some years and analytical models have been proposed to characterize this near-field motion. However there has been insufficient data with which to verify either the existence or the nature of this type of motion. The evidence of significant strongly correlated long-period motion provided by a preliminary analysis of the Lucerne Valley (SCE) record is of very great interest and concern to earthquake engineers. The objective of this project is: (1) to undertake a thorough study of the site, the instrument, and the recorded data so as to determine the accuracy of the Lucerne Valley earthquake record, (2) to develop appropriate correction algorithms for this instrument and to apply these to the measured ground motion record, and (3) to study the characteristics of the Lucerne Valley record any available comparable data to obtain a better understanding of the possible effects of near-field earthquakes on structural response.
