CAREER: Decoding the Enigmas of U.S. Seismic Hazard Via Multi-Scale, Multi-Physics Approaches to Paleoliquefaction Analysis

University Of Washington, Seattle WA

Investigators

Abstract

This Faculty Early Career Development Program (CAREER) project will contribute knowledge that reduces the uncertainty of seismic hazards in the United States, thereby promoting scientific progress and the nation's prosperity and welfare. Nationally, there are many regions in which seismic hazards are especially uncertain because the return periods of earthquakes are longer than the historic record. In other words, it is known that earthquakes have and will continue to occur, but because prior earthquakes predate human records and/or the advent of seismic instruments, the expected characteristics of future earthquakes are highly uncertain. In these locales, soil liquefaction caused by past earthquakes, termed "paleoliquefaction," may provide the only evidence from which information about the seismic-hazard can be determined, including earthquake magnitudes, locations, and recurrence-rates. As a result, U.S. building codes are heavily influenced by paleoliquefaction evidence, and in turn, so too is public safety. This award supports fundamental research to improve the analysis of paleoliquefaction, which at present suffers from limitations that can lead to highly erroneous results. The findings will not only advance paleoliquefaction analytics, but will also benefit the understanding of liquefaction hazards in general, thus further reducing earthquake impacts on the built and natural environments. In addition, an educational research component will investigate links between seismic risk perception and socio-psychological bias, leading to more effective educational platforms in natural hazards engineering. This CAREER project aims to remove ubiquitous barriers to the accurate inverse-analysis of paleoliquefaction, which will be achieved by bridging fundamental knowledge-gaps at three distinct scales. The research includes: (1) micro-scale physical-numerical investigation of the mechanics controlling the formation and morphology of fluidized dikes and sand boils; (2) meso-scale formulation of a coupled, mechanically-consistent liquefaction triggering and manifestation model; and (3) a macro-scale approach to probabilistically geolocate seismic sources from paleoliquefaction and assess their rupture magnitudes. An analytical framework developed from the fundamental research will then be applied to paleoliquefaction evidence in regions where enigmatic seismic-hazards significantly impact society. These include the Cascadia Subduction Zone of the Northwest U.S.; the New Madrid Seismic Zone of the Central U.S.; the South Carolina Coastal Plain of the Eastern U.S.; and Coastal New England in the Northeast U.S. Aided by physical and numerical multi-scale modeling, field testing, and unprecedented case-history data, this research will advance both paleoliquefaction analytics and the understanding of liquefaction hazards in general, thus reducing future earthquake impacts. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.