[ghsc-seminars] GHSC Seminar *HYBRID* - Andrew Makdisi, USGS, May 23, 2023

[Llenos, Andrea L]

Soil Liquefaction and its Role in Seismic Hazard and Risk

Speaker: Andrew Makdisi
                 Geologic Hazards Science Center
                 USGS
Location: hybrid (online and in person at 1711 Illinois St, Golden, CO, Rm 204)
                 *Non-USGS visitors welcome! Please bring a photo ID and arrive early to allow time to go through building security*
Date/Time: Tuesday, May 23, 2023, 10-11AM MDT

Abstract: Ground failure due to soil liquefaction poses substantial risks to the built environment and has caused significant damage in past earthquakes to buildings, roads, bridges, critical lifelines, dams, embankments, and other critical infrastructure. Characterizing liquefaction hazards in engineering practice is complicated by many challenges, mainly due to substantial uncertainties in (1) characterizing the presence, spatial extent, and cyclic properties of liquefaction-susceptible soils, (2) estimating the amplitude, frequency content, and duration of strong ground shaking likely to impact the site, and (3) incorporating soil-structure interaction effects to estimate the impacts of liquefaction on the structure or asset of interest. These cascading uncertainties can lead us to consider how liquefaction hazards fit into the broader concept of performance-based earthquake engineering (PBEE), which has increasingly become the basis of many building codes and seismic provisions for structural engineering applications (yet notably, less so for geotechnical applications). This presentation considers the current state of practice of liquefaction hazard assessment within the context of seismic performance, initially providing background on how we collectively define “acceptable performance” in earthquake engineering, and the various strategies for establishing performance objectives and bases of design. In doing so, I hope to motivate and present a more rigorous strategy for assessing liquefaction known as probabilistic liquefaction hazard analysis (PLHA), which makes use of and extends the USGS National Seismic Hazard Model to account for many of the aforementioned complexities in liquefaction, and assess liquefaction hazards in terms of annualized probabilities of occurrence. I’ll further discuss how PLHA can be used to characterize the implied liquefaction performance levels we get from our current building codes, and subsequently how PLHA can be used to develop more refined, consistent, and risk-targeted performance levels in future iterations of seismic provisions.

Bio: Andrew Makdisi joined the Geologic Hazards Science Center in 2021 as a research civil engineer, specializing in seismic hazard and risk characterization as it relates to geotechnical earthquake engineering, specifically soil liquefaction and ground failure. Andrew’s work at the GHSC contributes primarily to the Engineering & Risk (ERP) and National Seismic Hazard Model (NSHM) projects, focusing on improving the NSHM through the implementation of non-traditional ground motion intensity measures, extending the NSHM to consider downstream seismic hazard and risk in various ERP project efforts, and incorporating both of these aspects into risk assessments and earthquake building code updates. He currently serves as a voting member and USGS liaison on the Building Seismic Safety Council (BSSC), tasked with updating the National Earthquake Hazards Reduction Program (NEHRP) seismic provisions for new buildings, and is leading a number of BSSC efforts focused on advancing geotechnical design provisions towards novel, risk-based design criteria. Andrew received his B.S. in Civil Engineering from the University of California, Davis in 2012, and his M.S. and Ph.D. in Civil Engineering from the University of Washington in 2016 and 2021, respectively. He also spent a few years as a practicing geotechnical engineer and is a registered professional engineer in the state of California.

For questions, comments, or speaker suggestions, please contact the GHSC Seminar Committee: Andrea Llenos <allenos at usgs.gov>, Benjamin Murphy <bmurphy at usgs.gov>, Lauren Schaefer <lschaefer at usgs.gov>


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