Dynamic analysis of a slope failure from the 6 August 1979 Coyote Lake, California, earthquake
Dynamic analysis of a slope failure from the 6 August 1979 Coyote Lake, California, earthquake
Bulletin of the Seismological Society of America (June 1983) 73 (3): 863-877
The earthquake displaced a slump and formed a fissure 20 m long; with vertical offsets of 9 mm and horizontal offsets of 18 mm. The slump is within 100 m of the Calaveras fault trace. Two strong-motion records were written in the vicinity. These records combined with measurements of the slope, estimates of the material properties, and a dynamic numerical model based on the Newmark analysis of seismic slope stability to calculate a predicted displacement for the landslide. A displacement of 27 mm, calculated using the N50 degrees E component of the Gilroy #6 record, is in excellent agreement with the displacement measured in the field (21 mm). However, displacements of only 0.12 mm, calculated using the 250 degrees component of the Coyote Creek strong-motion record, reflect significant local variations in seismic shaking intensity. Because strong-motion records and slope failures rarely coincide, this landslide is an important test case for studying the dynamics of seismically induced landslides, as well as a warning that local seismologic variations need to be considered in any design applications.--Modified journal abstract.