GSA Connects 2021 in Portland, Oregon

Paper No. 231-13
Presentation Time: 4:55 PM


STAISCH, Lydia1, WATT, Janet2, WITTER, Robert3, PERKINS, Jonathan4, BROTHERS, Daniel S.5, DURA, Tina6, GOLDFINGER, Chris7, GRANT, Alex8, HAWKES, Andrea D.9, HILL, Jenna C.5, KELSEY, Harvey M.10, SHERROD, Brian L.11, ENGELHART, Simon E.12, ENKIN, Randy13, GOMBERG, Joan11, HAMILTON, Tark13, HONG, Isabel14, JAFFE, Bruce15, GARRISON-LANEY, Carrie16, LA SELLE, SeanPaul17, MEIGS, Andrew18, MELGAR, Diego19, NIEMINSKI, Nora20, PADGETT, Jason S.21, PATTON, Jason R.22, PEARL, Jessie23, PILARCZYK, Jessica21, SAHAKIAN, Valerie J.24, STANTON, Kelsay25 and WALTON, Maureen26, (1)U.S. Geological Survey, 2130 SW 5th Ave, Portland, OR 97201, (2)USGS Pacific Coastal and Marine Science Center, U.S. Geological Survey, 2885 Mission Street, Santa Cruz, CA 95060, (3)Alaska Science Center, U.S.G.S., Anchorage, AK 99508, (4)U.S. Geological Survey, Geology, Minerals, Energy, and Geophysics Science Center, P.O. Box 158, Moffett Field, CA 94035, (5)U.S. Geological Survey, Pacific Coastal and Marine Science Center, 2885 Mission Street, Santa Cruz, CA 95060, (6)4044 Derring Hall, 926 W Campus Dr, Blacksburg, VA 24061-1040, (7)College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Ocean Admin Bldg 104, Corvallis, OR 97331, (8)U.S. Geological Survey, 345 Middlefield Road, Menlo Park, CA 94025, (9)Geology & Geophysics Department, Woods Hole Oceanographic Institution, MS #22, 266 Woods Hole Rd, Woods Hole, MA 02543, (10)Geology Department, Humboldt State University, Arcata, CA 95521, (11)Earthquake Science Center, U.S. Geological Survey, University of Washington, Box 351310, Seattle, WA 98195, (12)Department of Geography, Durham University, Durham, United Kingdom, (13)Natural Resources Canada, Sidney, BC V8L 4B2, Canada, (14)Simon Fraser, Burnaby, BC V5A 1S6, Canada, (15)US Geological Survey, 2885 Mission Street, Santa Cruz, CA 95060, (16)Washington Sea Grant, Seattle, WA 98105, (17)US Geological Survey, Pacific Coastal and Marine Science Center, 2885 Mission Street, Santa Cruz, CA 95060, (18)Oregon State University, College of Earth, Ocean, Atmospheric Science, Corvallis, OR 97330, (19)University of Oregon, Eugene, OR 97403, (20)U.S. Geological SurveyPacific Coastal & Marine ScienceCenter, 2885 Mission St, Santa Cruz, CA 95060-5756, (21)Department of Earth Sciences, Simon Fraser University, Burnaby, BC V5A 1S6, Canada, (22)Conservation, California Geological Survey, 801 K St., Sacramento, CA 95814, (23)Seattle, WA 98195, (24)Department of Earth Sciences, University of Oregon, 2357 Grant St, Eugene, OR 97405, (25)Earth and Space Sciences, University of Washington, Seattle, WA 98195, (26)U.S. Geological SurveyPacific Coastal & Marine Science Ctr, 2885 Mission St, Santa Cruz, CA 95060-5756

The lack of historic seismicity along the Cascadia subduction zone (CSZ) fuels the uncertainty of the megathrust rupture process and resulting hazards in the US and Canadian Pacific Northwest. Diverse types of paleoseismic proxies uniquely record different aspects of the earthquake rupture process. Thus, margin-wide integration of paleoseismic proxy records leverages these unique transcripts to provide a richer understanding of past earthquake variability in time and space. In a series of virtual workshops, the USGS Powell Center research group on CSZ earthquake science and hazards have compiled paleoseismic records of coseismic coastal land-level change, tsunami inundation, and ground shaking proxies such as landslides, liquefaction, and turbidites. To consistently integrate different datasets, we constructed ranking schemes to quasi-quantitatively evaluate the quality of geochronologic age control and certainty of earthquake evidence at 49 coastal land level change sites, 81 tsunami sites, 76 terrestrial paleoseismic shaking sites, and 13 marine paleoseismic shaking sites. At each site, we evaluated how well geochronologic samples and results (14C dates, stratigraphy, geological context etc.) constrain the timing of candidate earthquake events. Similarly, we applied an evidence quality ranking scheme to assess how certain the observations of coastal land-level change, tsunami inundation, and strong ground motion were the result of a CSZ megathrust earthquake source. We also focused on historic records of non-local events, such as the 1964 Alaska earthquake and the 1992 Cape Mendocino earthquake, to identify the characteristics of distal subduction zone earthquakes and small local events, respectively, in the paleoseismic record. In the future we plan to identify the likely rupture characteristics of major CSZ earthquakes during the Holocene and to synthesize paleoseismic, geophysical, and instrumental datasets to identify the existence and persistence of rupture boundaries along the subduction zone.