Description:

In the wrong place at the wrong time: Effects of local soil conditions on seismic hazards

Abstract

The geologic structure near the ground surface exerts a significant influence on the amplitude, frequency content, and duration of earthquake ground motions (GMs). This phenomenon is known as site effects, and past earthquakes have shown that it can exacerbate damage to the built environment. Site response models can numerically capture site effects on GMs. Recent advances in site response modeling have enabled site-specific evaluations of seismic hazards for critical infrastructure and nonergodic ground motion models. However, challenges associated with two main modeling components of site response analysis remain to be addressed: (1) the parameterization of near-surface attenuation or damping, and (2) the selection of hazard-consistent input ground motions. This seminar will explore these new frontiers in site response modeling, identifying current limitations and providing recommendations to obtain unbiased site response estimates. The first frontier examines an advanced parameterization of energy dissipation in soils. Rethinking damping metrics in site response analysis allows for the integration of the multi-scale and multi-physics nature of near-surface attenuation mechanisms taking place in the field. The second frontier challenges the ability of traditional protocols of input motion selection to result in a seismic loading that is both, representative of the seismic hazard at the site and compatible with the assumed reference rock conditions in the numerical model. The aforementioned areas have the potential to shift paradigms in the assessment of seismic hazards, shaping next-generation ground motion modeling efforts and improving the characterization of site effects.

Bio

Ashly Cabas is an Assistant Professor in the Department of Civil, Construction, and Environmental Engineering at North Carolina State University. She completed her undergraduate studies at Universidad Católica Andrés Bello (UCAB) in Caracas, Venezuela, and she earned her M.S. and Ph.D. in Civil Engineering at Virginia Tech. Dr. Cabas' research interests are interdisciplinary with a focus on geotechnical aspects of earthquake engineering. Her research team works on site-specific seismic hazard assessment, the characterization of variability and uncertainty in site response analysis, and geohazards such as liquefaction-induced lateral spreading. Dr. Cabas was awarded the 2021 EERI Shah Family Innovation Prize and her group’s work has been recognized with the EERI best paper awards in 2014 and 2018. She was recently elected as a member of the Board of Directors of the Seismological Society of America (SSA) and has joined NSF-sponsored GEER teams in response to the 2018 Mw 7.1 Alaska, and 2021 Mw 7.2 Haiti earthquakes. Her research program has been funded by the USGS, NSF, PG&E, and the Alaska DOT, while contributing to international collaborations with the GFZ German Research Center for Geosciences, and the IFSTTAR in France. Dr. Cabas was selected as a 2021 NCSU Impact Scholar, 2021 New Faces in ASCE Geo-Institute, and Fellow for the NSF Enabling the Next Generation of Hazards and Disasters Researchers Fellowship Program.