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In the U.S. Pacific Northwest (PNW), the historic earthquake record is often insufficient to provide inputs to seismic-hazard analyses or to inform ground-motion predictions for certain seismic sources (e.g., the Cascadia Subduction Zone, CSZ). As a result, paleoseismic studies are commonly used to infer information about the seismic hazard. However, among the many forms 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 paper: (i) reviews current paleoliquefaction inverse-analysis methods and their limited, prior applications in the PNW; (ii) compiles all PNW paleoliquefaction evidence from the literature into a GIS database, resulting in data from 185 study sites (e.g., feature locations, types, sizes, and ages); and (iii) develops maps – specific to the CSZ – that forecast paleoliquefaction for 30 different simulations of a CSZ event. These maps can be used to guide field explorations for new evidence, such that they are conducted efficiently and strategically, considering the apparent utility of evidence toward constraint of CSZ ground-motion models. Of additional utility, this process provides regional ground-motion predictions for physics-based simulations of an M9 event, to include expected site effects. Collectively, the maps of expected shaking intensity and liquefaction may be useful in downstream hazard modelling, regional loss estimation, policy development, and science communication. Ultimately, as more paleoliquefaction evidence is identified and studied, better constraint of regional ground-motion hazards will result. Version 2 (this posting) supersedes Version 1 (10.17603/ds2-jm19-2w09). Updates include GIS rasters that provide regional ground-motion intensity predictions (PGA, PGV) for 30 physics-based simulations of an M9 event, to include expected site effects
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From information to public preparedness in the Cascadia Subduction Zone: Examining risk communication outcomes in Metropolitan Portland, OR
A Cascadia Subduction Zone (CSZ) earthquake will cause widespread damage along the Pacific Northwest (PNW) coast of the United States. It is, therefore, crucial to understand how to reduce future impacts across this region and assess current levels of household preparedness. Here, we examine whether decades of risk and preparedness campaigns have established protective knowledge and promoted hazard adjustments for residents of the Portland, Oregon metropolitan (PDX) region, an area where risk and preparedness campaigns have been increasing over the last decade. We also explore how PDX preparedness levels compare to those in other PNW regions using analogous data from multiple surveys over a 20-year time interval and assess PDX respondent’s perceptions of risk information sources. We find that 63% of PDX residents do not intend to “Drop, Cover, and Hold On” (DCHO) when earthquake shaking starts and that, although residents are generally aware of earthquake hazards in the area, they are less aware of the specific risks for their homes. Furthermore, PDX residents’ preparedness levels seem to be comparable to those recently surveyed in Washington, but somewhat less than those surveyed two decades ago in California, though more comprehensive data are needed to verify these results. We also find that people rate risk information provided by emergency managers and their websites as more accurate, understandable, relevant, and new than other sources. Our results suggest that significant gaps remain in translating broad awareness of the CSZ earthquake into personal knowledge and preparedness. This work provides guidance to PDX emergency educators for more targeted messaging and provides methods to measure preparedness variables in other regions for future comparisons. By paying close attention to preparedness gaps, local officials can use their limited resources more effectively to develop strategies to inform their communities and improve preparedness before a major earthquake strikes.
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- Award ID(s):
- 1663642
- PAR ID:
- 10367133
- Publisher / Repository:
- SAGE Publications
- Date Published:
- Journal Name:
- Earthquake Spectra
- Volume:
- 38
- Issue:
- 2
- ISSN:
- 8755-2930
- Page Range / eLocation ID:
- p. 1223-1253
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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