Earthquake Hazards, Ground Motions and Dynamic Response: On-Demand
Earthquakes represent a hazard to dams in many parts of the United States and therefore are of interest to design engineers and dam safety officials. The hazard from earthquakes includes strong shaking, fault rupture displacements, reservoir seiche and earthquake-induced landslides, all potentially damaging to dams and reservoirs. This webinar will discuss the physics and geology of the earthquake process and the methods used to identify seismic hazards in the field such as identifying geologic indicators of past earthquakes. The factors that control the earthquake ground motion at a site and the approaches used to predict ground motions for engineering analysis will be discussed. The intensity measures most commonly used to describe ground motions will be discussed along with the use and modification of motions for engineering analyses of dams. Finally, methods used to predict the dynamic response of embankment dams and their soil foundations to earthquake motions will be presented.
William A. Fraser
Retired, CA Division of Safety of Dams
William A. Fraser has worked his entire 33-year career in engineering geology related to the design, construction and maintenance of dams. While with the California State Water Project in the 1980’s he was involved in seismic stability investigations of several large dams, including a detailed investigation of the structural geology and piezometric condition at Castaic Dam, north of Los Angeles. He also performed design investigations for several large dams, including the proposed 300-foot high Los Banos Grandes Reservoir.
In 1988, William began at the Division of Safety of Dams and has been working in the design review and construction inspection of dams for the past 26 years, including almost 20 years as the Chief Geologist. He has worked on essentially all dams built in California during this period, including Diamond Valley, Seven Oaks, Los Vaqueros, Olivenhain, and New Calaveras dams, performing both site geotechnical characterizations and seismic hazard analyses. He has also been involved in seismic stability evaluations of numerous dams, some leading to stabilization efforts such as Lopez, San Pablo, Big Tujunga, and Perris dams.
William has been personally involved in over 200 dam projects in California. He is experienced all methods of site exploration, site characterization techniques for engineering analyses, and dam design options relevant for geologic conditions. He is also experienced in construction geology issues such as foundation acceptance and grouting. He is thoroughly familiar with paleoseismic fault investigations and seismic hazard analyses techniques; and has developed several policy-level guidelines for specifying ground motions for the purposes of dam safety assessments.
Lelio H. Mejia, PhD, PE, GE
Principal Engineer and Vice President, AECOM
Dr. Mejia is a registered civil and geotechnical engineer with over 30 years of experience in geotechnical and earthquake engineering. His main fields of expertise include dam engineering, soil liquefaction, earthquake ground motions, soil-structure interaction, and soil improvement.
He has directed the investigations and seismic stability studies of over 30 large earth dams and has been involved in the design and construction of over 15 major dam projects. He developed numerical techniques for the three-dimensional dynamic response analysis of rock and earthfill dams, and has conducted research on the applicability of two-dimensional and three-dimensional finite element techniques and fully nonlinear models to the dynamic response analysis of dams and earth structures. As a product of his research and project work, he has over 75 publications to his credit in refereed journals and conference proceedings.
He has served on technical review boards for the US Bureau of Reclamation, the US Army Corps of Engineers, and the California Department of Water Resources on various dam projects, and for other owners on various engineering projects.