- ©2000. AAPG/DEG
Ground-penetrating radar (GPR) was used to investigate the internal structure of two large landslides in Anchorage, Alaska that resulted from the great 1964 earthquake. The Government Hill and Turnagain Heights landslides occurred in similar stratigraphic and geographic settings, yet the style of ground deformation is different at each site. GPR data are compared with previous investigations and are shown, under certain conditions, to have utility in the identification of ancient landslides. Reflection surveys accurately reproduced the subsurface geometry of horst and graben structures and imaged finer scale features such as ground cracks and fissures. Where more complete disintegration of the bluff occurred, GPR reflections from within the slide mass are generally chaotic and include no recognizable evidence of the original stratigraphy. Common midpoint surveys estimated GPR velocity in the sediment and allowed the conversion of travel times to depths.
Walter Barnhardt is a research geologist with the Coastal and Marine Geology Program of the U.S. Geological Survey in Menlo Park, California. He received a BS in geology from the College of William and Mary and an MS and PhD in geological sciences from the University of Maine. Dr. Barnhardt's research focuses on the geomorphology, sedimentology, and late Quaternary stratigraphy of coastal environments.
Robert Kayen is a research civil engineer at the United States Geological Survey (USGS) in Menlo Park, California. He serves as project chief at the USGS Coastal and Marine Geology Team for multidisciplinary earthquake hazard studies in the Pacific Northwest. He is on the editorial board of the American Society of Civil Engineers Journal of Geotechnical and Geoenvironmental Engineering . Kayen received a PhD in civil engineering from the University of California at Berkeley and an MS in geology. Currently, he is collaborating with Pacific Gas and Electric Company to quantify potential earthquake ground-deformations in San Francisco Bay area soils and assess the risk to buried utilities.