Earthquake Hazards, Ground Motions and Dynamic Response: On-Demand

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Speakers: Lelio H. Mejia, Ph.D., P.E., G.E., Principal Engineer and Vice President, AECOM; and William A. Fraser, Retired, CA Division of Safety of Dams

PDHs: This webinar is eligible for 2 PDH credits.

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

Senior Principal

Geosyntec Consultants, Inc.

Dr. Lelio Mejia is a registered civil and geotechnical engineer with more than 35 years of experience in dam engineering, soil liquefaction, earthquake ground motions, soil-structure interaction, and soil improvement. He is a senior principal with Geosyntec Consultants and leads the firm’s Western U.S. dams and levees practice.

Lelio has directed the investigations and seismic stability evaluations of more than 25 large earth dams and has been involved in the design and construction of more than 15 major dam projects worldwide. He has served on multiple prestigious technical review boards and expert panels for U.S. federal and state agencies, water and power utilities, and other owners on various dam projects worldwide. He has led the design and helped manage the construction of several dam projects, including projects with more than $300 million in construction costs.
Lelio currently serves as the chair of the United States Society on Dams Earthquakes Committee and as a vice chairman of the International Commission on Large Dams Committee on Seismic Aspects of Dam Design. He was a member of the National Academies Committee for the State of the Art and Practice in Earthquake Induced Soil Liquefaction Assessment, a secretarial appointee to the Advisory Committee on Structural Safety of Department of Veterans Affairs Facilities, and chair of the Governance Board of the National Network for Earthquake Engineering Simulation. Lelio has been a lecturer of geotechnical earthquake engineering and a member of the editorial board for the American Society of Civil Engineers Journal of Geotechnical Engineering and was elected to the National Academy of Engineering.