A Screen Analysis Procedure for Seismic Slope Stability

Site-specific seismic slope stability analyses are required in California by the 1990 California Seismic Hazards Mapping Act for sites located within mapped hazard zones and scheduled for development with more than four single-family dwellings. A screen analysis is performed to distinguish sites for which only small ground deformations are likely from sites for which larger, more damaging landslide movements could occur. No additional analyses are required for sites that pass the screen, whereas relatively detailed analyses are required for sites that fail the screen. We present a screen analysis procedure that is based on a calibrated pseudo-static representation of seismic slope stability. The novel feature of the present screen procedure is that it accounts not only for the effects of ground motion amplitude on slope displacement, but also accounts for duration effects indirectly via the site seismicity. This formulation enables a more site-specific screen analysis than previous formulations that made a priori assumptions of seismicity/duration. This screen procedure has recently been adopted by the Landslide Hazard Implementation Committee for implementation by practicing engineers and engineering geologists in southern California.