The Search for Geologic Evidence of Distant-Source Tsunamis Using New Field Data in California Meters from shore A’ 75 100 125 150 175 200 225 250 275 300 325 350 2.0 1.5 AVD88 AVD88 1.0 N 0.5 0 Elevation, in meters above -0.5 -1.0 -1.5 Open-File Report 2013–1170–C California Geological Survey Special Report 229 U.S. Department of the Interior U.S. Geological Survey FRONT COVER: A photograph of two scientists collecting gouge core samples in the field, a photograph of a core containing the 1946 tsunami deposit (upper sand unit) at Half Moon Bay, and a figure showing correlations between layers in cores along a transect. The SAFRR (Science Application for Risk Reduction) Tsunami Scenario Stephanie Ross and Lucile Jones, Editors The Search for Geologic Evidence of Distant-Source Tsunamis Using New Field Data in California By Rick Wilson, Eileen Hemphill-Haley, Bruce Jaffe, Bruce Richmond, Robert Peters, Nick Graehl, Harvey Kelsey, Robert Leeper, Steve Watt, Mary McGann, Don Hoirup, Catherine Chagué-Goff, James Goff, Dylan Caldwell, and Casey Loofbourrow Open-File Report 2013-1170–C California Geological Survey Special Report 229 U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior SALLY JEWELL, Secretary U.S. Geological Survey Suzette M. Kimball, Acting Director U.S. Geological Survey, Reston, Virginia 2014 For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment—visit http://www.usgs.gov or call 1–888–ASK–USGS For an overview of USGS information products, including maps, imagery, and publications, visit http://www.usgs.gov/pubprod To order this and other USGS information products, visit http://store.usgs.gov Suggested citation: Wilson, R., Hemphill-Haley, E., Jaffe, B., Richmond, B., Peters, R., Graehl, N., Kelsey, H., Leeper, R., Watt, S., McGann, M., Hoirup, D., Chague-Goff, C., Goff, J., Caldwell, D., and Loofbourrow, C., 2014, The search for geologic evidence of distant source tsunamis using new field data in California, chap C of Ross, S.L., and Jones, L.M., eds., The SAFRR (Science Application for Risk Reduction) tsunami scenario: U.S. Geological Survey Open- File Report 2013-1170-C, 122 p., http://dx.doi.org/10.3133/ofr20131170c. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner. ISSN 2331-1258 (online) ii STATE OF CALIFORNIA EDMUND G. BROWN, JR. GOVERNOR THE NATURAL RESOURCES AGENCY JOHN LAIRD SECRETARY FOR RESOURCES DEPARTMENT OF CONSERVATION MARK NECHODOM DIRECTOR CALIFORNIA GEOLOGICAL SURVEY JOHN G. PARRISH, Ph.D. STATE GEOLOGIST iii Page intentionally left blank iv Contents Abstract ....................................................................................................................................................................... 1 Introduction ................................................................................................................................................................. 2 Significant Historical Tsunamis ................................................................................................................................... 3 Tsunami Deposit Investigation .................................................................................................................................... 7 Site Selection .......................................................................................................................................................... 8 Existing Geological and Geotechnical Literature.................................................................................................. 8 Aleutian-Alaska Subduction Zone III (AASZ III) Numerical Tsunami Model ......................................................... 8 Additional Reference Data ................................................................................................................................... 8 Tsunami Deposit Identification ................................................................................................................................. 9 Suspension Grading in Tsunami Deposits ......................................................................................................... 11 Reconnaissance Fieldwork .................................................................................................................................... 12 Reconnaissance Field Sites North of Point Conception, 2011–2012 ................................................................. 17 Bodega Bay (Doran Marsh) ............................................................................................................................ 17 Point Reyes 1 (Barries Bay) ........................................................................................................................... 19 Point Reyes 2 (Home Bay) ............................................................................................................................. 23 Bolinas Lagoon .............................................................................................................................................. 29 Rodeo Lagoon ................................................................................................................................................ 30 Scott Creek .................................................................................................................................................... 33 Carmel River Lagoon and Wetland Natural Preserve ..................................................................................... 38 Los Osos Creek (Morro Bay) .......................................................................................................................... 41 Sweet Springs Nature Preserve (Morro Bay) ................................................................................................. 47 Morro Estuary Natural Preserve (Morro Bay) ................................................................................................. 56 San Luis Obispo Creek (Avila Beach) ............................................................................................................ 63 Reconnaissance Field Sites South of Point Conception, 2012 .......................................................................... 66 Point Mugu ..................................................................................................................................................... 66 Seal Beach ..................................................................................................................................................... 69 Los Penasquitos ............................................................................................................................................. 70 Tijuana Estuary (Tijuana River National Estuarine Research Reserve; Oneonta Slough) ............................. 72 Detailed Site Evaluations ....................................................................................................................................... 76 Crescent City Marshes (primary summary by Eileen Hemphill-Haley) ............................................................... 76 Introduction .................................................................................................................................................... 76 Field Localities ............................................................................................................................................... 76 Conclusions .................................................................................................................................................... 85 Pillar Point Marsh (primary summary by Bruce Jaffe and Bruce Richmond) ...................................................... 85 Introduction .................................................................................................................................................... 85 Field Studies .................................................................................................................................................. 87 Conclusions .................................................................................................................................................... 94 Carpinteria Salt Marsh (primary summary by Robert Peters)............................................................................. 94 Introduction .................................................................................................................................................... 94 Field Studies .................................................................................................................................................. 95 Historical and Prehistoric Conditions at Carpinteria Salt Marsh ..................................................................... 96 Candidate Tsunami Deposits ......................................................................................................................... 97 Normal and Suspension Grading ................................................................................................................. 101 Microfossils