The Los Angeles basin's sediments seem to moderate the type of ground motion that threatens single-story and low-rise buildings in a severe earthquake, a new study of data from the 1994 magnitude-6.7 Northridge quake has revealed.

The great 1857 Ft. Tejon earthquake (magnitude 7.8) which ruptured the San Andreas fault from central California to Cajon Pass was the largest earthquake to have hit southern California during the historic period. This great earthquake was followed by approximately 50 years of seismic quiet in the region west of Cajon Pass, including the Los Angeles basin.

New ground motion simulations for earthquakes on some of southern California's major faults show significant effects of the basin on both the amplitude and duration of long-period ground shaking (the "rolling motion" from earthquakes).

The Southern California Earthquake Center is collecting and interpreting geodetic survey data for southern California to monitor fault motions and earthquake potential. A major product of this work is a set of deformation velocity estimates (the rate at which the Earth's crust moves) for 287 sites in southern California. These new estimates reveal the horizontal component of deformation resulting from strain build-up and aseismic motions in the crust.

The Earthquake Center is planning a new series of paleoseismic studies of the San Andreas fault over the next few years. (Paleoseismology is a term that denotes the investigation of individual earthquakes well after their occurrence.) The San Andreas was the focus of the first paleoseismic studies in southern California by Kerry Sieh and others in the 1970s and 1980s. But with the inception of the Earthquake Center in 1991, the emphasis shifted to the Los Angeles metropolitan area and its many faults posing a hazard to the urban environment.