Seismically induced rock slope failures resulting from topographic amplification of strong ground motions: The case of Pacoima Canyon, California

摘要: Abstract The 1994 Northridge earthquake (Mw = 6.7) triggered extensive rock slope failures in Pacoima Canyon, immediately north of Los Angeles, California. Canyon is a narrow and steep canyon incised gneissic granitic rocks. Peak accelerations nearly 1.6 g were recorded at ridge that forms the left abutment Dam; peak bottom less than 0.5 g, suggesting occurrence topographic amplification. Topographic effects have been previously suggested to explain similarly high ground motions site during 1971 San Fernando earthquake. Furthermore, landslide concentrations observed area attributed unusually strong rather higher susceptibility sliding compared with nearby zones. We conducted field investigations stability back-analyses confirm impact amplification on triggering landslides Our results suggest falling would not possible under unamplified seismic conditions, which generated significantly lower number areas affected by landslides. In contrast, modelling using amplified shaking predicts failure distributions matching what occurred 1994. This observation confirms significant role for site, emphasises need select carefully inputs analyses.