USGS · 70197852
No abstract available.
Explore connections, maps & timelines
Manuel G. Bonilla. 1988. Minimum earthquake magnitude associated with coseismic surface faulting. https://doi.org/10.2113/gseegeosci.xxv.1.17
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
A large landslide failed catastrophically along steep, 90-m (300-ft) high bluffs overlooking the waters of Puget Sound at Tacoma, Washington, in April of 1949, three days after the region was struck by a magnitude 7.1 earthquake. The area of failure was investigated to estimate the static and seismic stability of the pre-earthquake slope and to identify factors that contributed to the failure. Results of static analyses suggest that the slope was marginally stable and that high ground-water conditions would have significantly reduced slope stability. The Newmark analysis of dynamic (seismic) slope stability was used to calculate predicted inertial displacements for the landslide for a range of possible material property and ground-water conditions. Comparison of predicted displacements with a reported displacement suggests that the ground motion could have initiated the large-scale failure. Results of the study provide a basis for discussion and comparison of similar bluffs in the Puget Sound region that may be susceptible to catastrophic, earthquake-induced slope failure.
Investigations of earthquakes world wide show that rock falls are the most abundant type of landslide that is triggered by earthquakes. An engineering classification originally used in tunnel design, known as the rock mass quality designation (Q), was modified for use in rating the susceptibility of rock slopes to seismically-induced failure. Analysis of rock-fall concentrations and Q-values for the 1980 earthquake sequence near Mammoth Lakes, California, defines a well-constrained upper bound that shows the number of rock falls per site decreases rapidly with increasing Q. Because of the similarities of lithology and slope between the Eastern Sierra Nevada Range near Mammoth Lakes and the Wasatch Front near Salt Lake City, Utah, the probabilities derived from analysis of the Mammoth Lakes region were used to predict rock-fall probabilities for rock slopes near Salt Lake City in response to a magnitude 6.0 earthquake. These predicted probabilities were then used to generalize zones of rock-fall susceptibility.
Faulure of rock slopes is a major cause of damage and casualties during moderate and strong earthquakes. This article presents a method for assessing the seismic stability of rock slopes, which can be applied on a regional scale, using data from existing maps, reports, aerial photographs, and reconnaissance-level field observations. The method is based on observed associations between landslide concentrations and slope characteristics in 24 earthquakes that occurred in various parts of the world.