Earthquakes can have devastating effects on communities, families, and societies as a whole. In the interest of saving lives and developing sustainable and resilient infrastructure, scientists and engineers are faced with the challenge of developing methods by which seismic hazards can be understood, quantified, and incorporated into seismic design. Jim's primary area of research focuses upon the prediction of earthquake-induced ground motion, an important component of any seismic hazard analysis. With a greater understanding of the level of ground motion expected during earthquakes, engineers will be better able to design earthquake-resistant structures, and ultimately improve our sustainability by reducing the loss of life and property during earthquakes.
Jim's research in earthquake engineering has focused on the statistical and theoretical modeling involved in site response analyses, ground-motion models, and probabilistic seismic hazard analyses. His research involves a balance between data-driven statistics and attention to the underlying physics of the models. Across his projects, his research philosophy has been to apply rigorous statistical methods upon large datasets, ultimately working towards improving models for predicting earthquake-induced ground motion. A secondary research interest of Jim's is engineering education, particularly on undergraduate geotechnical engineering courses, and he has been involved in multiple projects in this realm. Please visit the Publications page or his Google Scholar profile for further details on his work.
Site response analyses are used to estimate site-specific ground motions, as a function of the properties of the soil profile and the input motion at the base of the soil profile. These analyses attempt to capture the influence of near-surface geologic materials on seismic waves as they propagate from depth to the ground surface. Despite their broad usage in engineering practice, site response models are burdened with significant uncertainties. Jim has undertaken a number of projects involving ground motions from the data-rich Kiban-Kyoshin (KiK-net) network of vertical seismometer arrays in Japan. His work has sought to identify which parameters offer the greatest contributions to site response prediction uncertainty; to compare and quantify uncertainties in various site response models, modeling assumptions, input parameters, and input motion selection protocols; and to develop recommendations for the improvement of site response modeling. More locally, Jim has been involved in assessment of site response in the Boston basin, and the unique seismic hazards associated with sedimentary basins in the Central and Eastern United States.
A fundamental step in any seismic hazard analysis is the quantification of the expected levels of ground motions for potential earthquakes, as well as the uncertainties in the estimates. The expected level of ground motion may be estimated by a ground-motion model (GMM), which is a semi-empirical model that predicts the ground motion at a given location as a function of earthquake magnitude, distance from the earthquake source, site characteristics, and other variables. Compared to site response models (which are more site-specific in nature), GMMs offer predictions that can be applied over broader areas. Using a range of statistical methodologies, Jim developed a validation framework for GMMs, and used this approach to quantify the prediction accuracies of models released as part of the Next Generation Attenuation of Ground Motions (NGA-West) project. He also developed a methodology for estimating unknown source, path, and site parameters in GMMs, with the intent of making these models more accessible for engineering practitioners. Currently, he is working to improve the incorporation of site-specific geologic and ground motion data into the development of GMMs.
Probabilistic seismic hazard analyses
The purpose of probabilistic seismic hazard analyses (PSHAs) is to quantify the hazard due to earthquake ground shaking at a given location, by incorporating uncertainties in earthquake size, location, and rate of recurrence, and uncertainties in the level of ground motion. PSHAs are performed on a national basis for the development of the U.S. National Seismic Hazard Model by the U.S. Geological Survey (serving as the basis for building codes), as well as on a site-specific basis for critical infrastructure projects such as dams and nuclear power plants; Jim's research has addressed PSHAs at various scales. His work has sought to improve regional models for site response and seismic hazard in the Central and Eastern United States (with a recent project emphasizing the Atlantic and Gulf Coastal Plains), with the goal of informing future versions of the U.S. National Seismic Hazard Model. In addition, he has worked to advance the state-of-the-art of ground motion characterization and site response models in site-specific PSHAs, drawing from his consulting experience from a high-level PSHA at Idaho National Laboratory.
Geotechnical engineering education
As a professor at a predominantly undergraduate institution, Jim is deeply committed to undergraduate engineering education and methods by which student learning can be enhanced. His projects in the realm of geotechnical engineering education include: (1) the usage of pre- and post-course knowledge surveys to assess gains in student learning, (2) incorporation of natural disasters into the undergraduate civil engineering curriculum, and (3) the development and improvement of educational/research software for geotechnical engineering and earthquake engineering. Jim’s projects to develop free and open-source software have resulted in a number of products available for usage in the community, and may be accessed on the Software page.