Compilation and Forecasting of Paleoliquefaction Evidence for the Strength of Ground Motions in the U.S. Pacific Northwest: A Digital Dataset (Version 1)

In the U.S. Pacific Northwest (PNW), the historic earthquake record is often insufficient to provide inputs to seismic-hazard analyses (i.e., fault locations and magnitude-frequency relations) or to inform ground-motion predictions for certain seismic sources (e.g., the Cascadia Subduction Zone, CSZ). As a result, analyses of paleoseismic relics are commonly used to infer information about the seismic hazard. However, among the many types of coseismic evidence, soil liquefaction provides the best, if not only, evidence from which the intensities of previous ground motions may be constrained. Accordingly, the overarching goal of this research is to use paleoliquefaction to elucidate previous ground motions in the PNW – both for CSZ events and others – and to further constrain the locations, magnitudes, and recurrence rates of such ruptures. Towards that goal, this data product: (i) compiles all PNW paleoliquefaction evidence from the literature into a GIS package, resulting in data from 185 study sites (e.g., feature locations, types, sizes, and ages); and (iii) develops maps – specific to the CSZ – to guide field explorations for new evidence, such that these efforts are conducted efficiently and strategically. These maps consider both remote-sensing predictions of liquefaction susceptibility and the apparent utility of evidence toward constraint of CSZ ground-motion predictions. Of additional utility, the maps predict liquefaction regionally for various realizations of an M9 CSZ rupture, which may be useful in regional loss estimation, policy development, and science communication. Ultimately, as more paleoliquefaction evidence is identified and studied, better constraint of regional ground-motions in past earthquakes will result.