[ghsc-seminars] GHSC Seminar—TOMORROW—James Kaklamanos, Merrimack College, Tuesday, June 21st, 2022, 10–11am MT

[Boyd, Oliver S]

Advancing Site Response Estimation: Limitations of the One-Dimensional Assumption

Speaker: James Kaklamanos
               Associate Professor
               Department of Civil Engineering
               Merrimack College
Location: online/virtual only
Date/Time: TOMORROW, Tuesday, June 21st, 2022, 10–11am MT

Abstract: Site response—the effect of near-surface geologic materials on seismic waves—is an important phenomenon that contributes to the seismic hazard at a specific location. A major drawback of models for predicting site response is that they are associated with large uncertainties and have often been found to poorly replicate observed ground motions. In this seminar, insights from a large dataset of sites and ground motions from the Kiban-Kyoshin (KiK-net) network of vertical seismometer arrays in Japan will be discussed. Analyses are performed to identify which parameters offer the greatest contributions to site response prediction uncertainty, and to compare and quantify uncertainties in various one-dimensional (1D) site response models, modeling assumptions, input parameters, and input motion selection protocols. In the aggregate, site response models are shown to be biased towards underprediction at high frequencies, due to breakdowns in 1D wave propagation assumptions and/or poorly characterized soil properties.  Various physical hypotheses are tested for improving this persistent model bias, such as applying a depth-dependent seismic velocity gradient within layers. The results of this study provide statistical and physical insights for improvements to 1D seismic site response models and the identification of sites that may be well-modeled by the 1D assumption, with the ultimate goal of improving the accuracy of ground motion predictions in engineering practice.
[cid:7611c610-2a65-4c3d-b4ba-13b8d567871a]
Figure 1.  Map of the 114 KiK-net stations in Japan used in this site response evaluation study, along with predicted site response complexity using a model derived from geospatial data.

Bio: Jim Kaklamanos is an Associate Professor of Civil Engineering at Merrimack College in North Andover, Massachusetts. Prior to joining the Merrimack faculty, he obtained his degrees in Civil and Environmental Engineering from Tufts University (BSCE 2008, M.S. 2010, Ph.D. 2012). He specializes in geotechnical earthquake engineering, and his research focuses on the improvement of models for predicting earthquake-induced ground motions. Jim’s published work has included research on site response analyses, ground-motion prediction equations, uncertainty in earthquake engineering, and engineering education. He is a member of the Ground Motion Characterization Technical Integration Team for an ongoing probabilistic seismic hazard analysis at Idaho National Laboratory, and he has been honored as one of the Top Ten New Faces of Civil Engineering by the American Society of Civil Engineers in 2017, one of New Hampshire’s 40 Under Forty by the New Hampshire Union Leader in 2022, and a recipient of the 2022 Early Career Educator Award from the U.S. Universities Council on Geotechnical Education and Research (USUCGER).


GHSC Seminar Committee: Oliver Boyd <olboyd at usgs.gov>, Josh Rigler <erigler at usgs.gov>, Francis Rengers <frengers at usgs.gov>


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