CTD_DATABASE - Cascadia tsunami deposit database

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What does this data set describe?

Title: CTD_DATABASE - Cascadia tsunami deposit database
The Cascadia Tsunami Deposit Database contains data on the location and sedimentological properties of tsunami deposits found along the Cascadia margin. Data have been compiled from 52 studies, documenting 59 sites from northern California to Vancouver Island, British Columbia that contain known or potential tsunami deposits. Bibliographical references are provided for all sites included in the database. Cascadia tsunami deposits are usually seen as anomalous sand layers in coastal marsh or lake sediments. The studies cited in the database use numerous criteria based on sedimentary characteristics to distinguish tsunami deposits from sand layers deposited by other processes, such as river flooding and storm surges. Several studies cited in the database contain evidence for more than one tsunami at a site. Data categories include age, thickness, layering, grainsize, and other sedimentological characteristics of Cascadia tsunami deposits. The database documents the variability observed in tsunami deposits found along the Cascadia margin.
The database uses the Microsoft Excel spreadsheet program to present the data and is also available in text format (tab delimited) and as an ArcView coverage. (Some entries may be truncated in ArcView at 255 characters. Please refer to text or Excel formats for complete entries.) Data categories are located on the horizontal axis (columns) and the site locations on the vertical axis (rows). Initially, the sites are sorted by latitude, from north to south, although data may be sorted by any data category in Excel by the user. The format of the data often varies from publication to publication. Wherever possible, we have used the authors own words or descriptions. Where conversions are clear and simple, we converted data into standard formats appropriate for the category, such as decimal degrees for latitude and longitude or centimeters for deposit thickness. When a publication describes more than one tsunami deposit at a site, each deposit is catalogued separately (i.e. a separate row is used for each deposit). If significant differences in deposit characteristics are reported at different locations within a site, these are also catalogued separately. If an author uses one description to characterize several layers, these may be grouped into a single entry. None of the publications cited in the database cover all data categories. Many are limited in scope and cover only a few categories. In others, tsunami deposits were only a secondary theme of the paper. For some sites, there is only mention that a tsunami deposit was present, but no details are given.
  1. How might this data set be cited?
    Peters, Robert, Jaffe, Bruce, Gelfenbaum, Guy, and Peterson, Curt, 2003, CTD_DATABASE - Cascadia tsunami deposit database: Open-File Report 03-013, U.S. Geological Survey, Coastal and Marine Geology Program, Pacific Science Center, Santa Cruz, CA.

    Online Links:

    This is part of the following larger work.

    Peters, Robert, Jaffe, Bruce, Gelfenbaum, Guy, and Peterson, Curt, 2003.

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -127.846200
    East_Bounding_Coordinate: -122.710000
    North_Bounding_Coordinate: 50.508900
    South_Bounding_Coordinate: 40.619700
  3. What does it look like?
    http://geo-nsdi.er.usgs.gov/metadata/open-file/03-13/browse.png (PNG)
    ArcExplorer screen capture showing distribution of cataloged tsunami deposits from this database along with geographic reference layers showing coastlines, topography, and political boundaries, 750x554 pixels, 202k bytes
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 1987
    Ending_Date: 2002
    publication date
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: vector digital data
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      This is a Vector data set. It contains the following vector data types (SDTS terminology):
      • Entity point (314)
    2. What coordinate system is used to represent geographic features?
      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.000000. Longitudes are given to the nearest 0.000000. Latitude and longitude values are specified in Decimal degrees. The horizontal datum used is North American Datum of 1983.
      The ellipsoid used is Geodetic Reference System 80.
      The semi-major axis of the ellipsoid used is 6378137.000000.
      The flattening of the ellipsoid used is 1/298.257222.
  7. How does the data set describe geographic features?
    Description of a tsunami deposit
    The name of the location where the tsunami deposits are located, including state. The name may refer to the nearest easily recognized place name, such as a town, a body of water, or other geographic feature.
    grading describes textural changes in the vertical direction within a layer. Normal grading refers to fining upwards. Inverse grading refers to coarsening upwards.
    material other than sediment grains in a deposit, including plant material, shells or other macrofossils, artifacts, etc.
    Internal feature number. (Source: ESRI) Sequential unique whole numbers that are automatically generated.
    description of gradients in thickness (landward thinning, etc.) and continuity of the deposit.
    sorting is a measure of the variability of the grain sizes in the deposit and is usually characterized from well sorted (little variability) to poorly sorted (large variability). More quantitative statistical measures have not generally been reported in the Cascadia tsunami deposit literature. (Source: Folk, 1980)
    citing for reference that provided the data by author and year. Complete citing is listed in the reference section of this report and on the references worksheet in the database.
    Feature geometry. (Source: ESRI) Coordinates defining the features.

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Robert Peters
    • Bruce Jaffe
    • Guy Gelfenbaum
    • Curt Peterson
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
    Guy Gelfenbaum
    U.S Geological Survey
    345 Middlefield Road
    Menlo Park, CA

    (650) 329-5483 (voice)
    (650) 329-5198 (FAX)

Why was the data set created?

The Cascadia Tsunami Deposit Database is a compilation of published data on the location and sedimentary characteristics of tsunami deposits found along the Cascadia margin. It consolidates data from the earliest published reports on Cascadia tsunami deposits (e.g. Atwater, 1987, Reinhart and Bourgeois, 1987) to studies published or in press by the year 2002. This database and associated report is intended as a guide to the sedimentary features that characterize Cascadia tsunami deposits and to the locations where tsunami deposits have been found along the Cascadia margin. It also provides references for all of the tsunami deposits cited. The Cascadia Subduction Zone (CSZ) is situated off of the Pacific Northwest coast of North America, from Northern California to Vancouver Island, British Columbia (Figure 1). Great earthquakes (m > 8.0) on subduction zones have the potential to trigger large tsunamis. While not all subduction zones generate great earthquakes, it is believed that the CSZ has the potential to generate great earthquakes. The CSZ shares many features with other subduction zones that experience great earthquakes ( Heaton and Kanamori, 1984). Geologic evidence for great earthquakes along the CSZ include turbidites off the Cascadia margin (Adams, 1990) and stratigraphic evidence of sudden coastal subsidence (e.g. Atwater et al., 1995, Nelson and Peronius, 1996). Although no great earthquakes have occurred on the CSZ since European colonization of the Pacific Northwest in the mid 1800s, an Indian oral tradition from the Pacific Northwest predating written records alludes to great shaking of the earth and coastal flooding (Heaton and Snavely, 1985, Clague, 1995). Geologic evidence for large tsunamis along the Cascadia margin has only recently been recognized. Atwater (1987) published a report attributing anomalous sand layers in marsh sediments from southern coastal Washington to tsunamis generated by great earthquakes on the CSZ. Since this time, more than 50 studies have been published, documenting numerous sites containing confirmed or potential tsunami deposits and detailing deposit characteristics along the Pacific Northwest coast from Northern California to Vancouver Island, British Columbia ( Figure 2). This rapid increase in our knowledge of Cascadia tsunami deposits has led to a greater public awareness of tsunami hazards, and improved our ability to assess the risk from future tsunamis. Data from tsunami deposits have been included on tsunami inundation maps (e.g. Walsh et al., 2000). Tsunami deposits are a key component to the recognition and mitigation of tsunami hazards in the Pacific Northwest.

How was the data set created?

  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
    (process 1 of 2)
    Identification of CSZ Tsunami Deposits
    The studies cited in the database use a variety of sedimentary features to identify tsunami deposits in outcrops and cores. Preliminary identification of tsunami deposits is often based on the recognition of anomalous layers of sand in environments where the deposition of sand layers is unusual, such as coastal marshes or lakes (Reinhart and Bourgeois, 1987). Tsunamis can transport sand, cobbles, boulders and debris from offshore and from beaches and deposit it over coastal lowlands (Dawson, 1994). However, other energetic processes, such as river flooding or storm surges, may leave sandy deposits in otherwise low-energy environments (Nelson et al., 1996). Key sedimentary characteristics of the deposit are often cited to confirm a tsunami origin for the sand layer. While no single characteristic may universally be used to distinguish a tsunami deposit, the combination of several characteristics are often used to rule out other processes and leave little or no doubt as to a tsunami origin for the deposit. Tsunami deposits may be distinguished from river deposits by distinct biological markers, spatial distribution, sediment characteristics and geochemistry. The presence of marine or brackish water macro- and microfossils is used to infer a marine rather than river source for the deposit (Hemphill- Haley, 1995). Thinning and fining of the deposit landward are often used to suggest a marine surge rather than a river source for the deposit (Atwater, 1987; Benson et al., 1997). Flop-overs, which consist of the leaves and stems of herbaceous plants bent over by the flow, preserve information about flow direction and may indicate a landward-directed flow, suggesting a marine source (Atwater and Hemphill-Haley, 1997). The composition and texture of the sand grains has been used to differentiate between a coastal or upriver source (Darienzo and Peterson, 1990; Peterson and Darienzo, 1996). Geochemical indicators, such as bromine enrichment, have also been used to indicate a marine source for the deposit (Schlichting, 2000). Storm surge deposits are more difficult to distinguish from tsunami deposits because, similar to tsunami deposits, they also contain marine or brackish water macro- and microfossils, have saltwater chemistry, and thin and fine landward (Nelson et al., 1996). Some studies use distance inland to indicate a tsunami source, arguing that it is not likely that storm waves or a storm surge could deposit sand inland to the extent of the deposit (Clague et al., 2000). Reinhart (1991) argues that in protected tidal channels, storms are unlikely to suspend the volume of sediment necessary to produce the deposits observed. When layers are present, their number and thickness are sometimes used to differentiate between a tsunami and storm deposit (Williams and Hutchinson, 2000, Witter, in press). Tsunami deposits tend to have several relatively thick normally graded beds, suggesting deposition from suspension by successive waves in the tsunami wave train, while storm deposits may be expected to have thinner and more numerous laminations from higher frequency but lower energy storm waves (Nelson et al., 1996b). Abramson (1998) uses the presence of rip-up clasts in the deposit to indicate the higher energy deposition of a tsunami. Association of the sand layer with paleoseismicity is often used to link a sand layer to a tsunami source. Coseismic coastal subsidence may accompany great subduction zone earthquakes (Atwater, 1996). Association of the sand layer with evidence of coseismic subsidence is often key to the identification of the sand layer as a tsunami deposit (Atwater, 1987, Darienzo and Peterson, 1990). This is usually seen as a buried soil or layer of peat, representing a marsh surface that formed above the reach of high tide, abruptly overlain by a layer of sand (the tsunami deposit), which is then overlain by tidal flat mud. Linking a sand layer to liquifaction features also may tie a potential tsunami deposit to a seismic event (Atwater, 1992). The presence of stems of herbaceous plants in growth position within the deposit is used to indicate approximate coincidence of deposition of the sand layer with submergence of the marsh surface (Atwater, 1992). Deposit geometry and the number of sand layers present in a core or outcrop are sometimes used to differentiate between a deposit produced by a tsunami from a great earthquake on the CSZ and one left by a tsunami with a distant source. Carver et al. (1996) proposed using deposit extent and thickness to differentiate CSZ tsunamis from distant tsunamis by comparing them to deposits left by historic distant tsunamis. Witter (2001) uses the estimated 500-540 year average recurrence interval for great CSZ earthquakes (Atwater and Hemphill Haley, 1997) to suggest that at least two out of four sand layers in a 600 year interval were deposited by distant tsunamis or storm surges. In lake deposits, the source of the tsunami (local or distant) may not be evident in the sediments (Clague, 1997).
    (process 2 of 2)
    Metadata imported. Data sources used in this process:
    • C:\DOCUME~1\VPASKE~1\LOCALS~1\Temp\xml1D4.tmp
  3. What similar or related data should the user be aware of?

How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?
  2. How accurate are the geographic locations?
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
    It is the goal of the authors that the database be comprehensive. The database currently cites 53 papers documenting 60 sites where known or potential tsunami deposits have been reported along the Cascadia margin (Figure 2). All known journal articles pertaining to specific sites along the Cascadia margin and published in English by the time of submission have been included. While every attempt has been made to include all theses and conference or symposium abstracts and proceedings that pertain to Cascadia tsunami deposits, the limited availability and inadequate referencing of some of these publications has made some omissions likely. Also, some conference abstracts that were superceded by journal publications were omitted if they did not contain any additional information. Similarly, if a USGS open file report was superceded by a USGS professional paper, only the professional paper was included. The Cascadia Tsunami Deposit Database documents the variety found in tsunami deposits along the Pacific Northwest coast. It contains data on the age, number of deposits, sedimentary characteristics and identifying features of Cascadia tsunami deposits. It includes data from Northern California, north of the Mendocino triple junction through Vancouver Island, British Columbia, Canada. While the focus of the database are deposits from tsunamis that originate from earthquakes on the CSZ, data from historical tsunami deposits originating from trans-oceanic tsunamis are included for comparison. Tsunami deposits located in the Puget Sound area that are not believed to be of a Cascadia origin are not included in the database.
  5. How consistent are the relationships among the observations, including topology?
    The data derive from a wide variety of studies with differences in focus, scope, and intent. Details concerning techniques, errors, difficulties, inconsistencies, variability, and potential alternate interpretations of the data are beyond the scope of this report. These are usually site-specific and the original citation should be consulted. This report contains data from both peer-reviewed journals and from publications not typically subjected to extensive peer review. Techniques varied widely among the various studies and the accuracy and precision between separate entries may not be comparable. No attempt has been made in this report to quantify errors. The exception is in dating the deposits, where the errors reported in the publications are included. Even these may not be comparable due to differences in material dated, sampling techniques, or in the case of ages reported in calendar years, the calibration curve used and the error estimation method (Stuvier and Becker, 1986, 1993). It is recommended that the original reference, supplied for each entry, be consulted before using data compiled in this report.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Physical materials are under controlled on-site access.
If available, access to physical samples is described in the "WR CMG Sample Distribution Policy" at http://walrus.wr.usgs.gov/infobank/programs/html/definition/sample-dist-policy.html
Public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution. Please recognize the U.S. Geological Survey as the originator of the dataset.
Some USGS information accessed through this means may be preliminary in nature and presented without the approval of the Director of the USGS. This information is provided with the understanding that it is not guaranteed to be correct or complete and conclusions drawn from such information are the responsibility of the user.
  1. Who distributes the data set? (Distributor 1 of 1)
    Guy Gelfenbaum
    U.S Geological Survey
    345 Middlefield Road
    Menlo Park, CA

    (650) 329-5483 (voice)
    (650) 329-5198 (FAX)
  2. What's the catalog number I need to order this data set? Downloadable Data: USGS Open-File Report 03-13; Cascadia tsunami deposits database (ctd_database)
  3. What legal disclaimers am I supposed to read?
    Although these data have been used by the U.S. Geological Survey (USGS), U.S. Department of the Interior (DOI), no warranty expressed or implied is made by the U.S. Geological Survey as to the accuracy of the data. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of these data or related materials.
    Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
  4. How can I download or order the data?
  5. What hardware or software do I need in order to use the data set?
    These data are available in Environmental Systems Research Institute (ESRI) shapefile format. The user must have ArcGIS or ArcView 3.0 or greater software to read and process the data file. In lieu of ArcView or ArcGIS, the user may utilize another GIS application package capable of importing data. A free data viewer, ArcExplorer, capable of displaying the data is available from ESRI at www.esri.com.

Who wrote the metadata?

Last modified: 08-Dec-2006
Metadata author:
U.S Geological Survey
Attn: Robert Peters
Pacific Science Center
Santa Cruz, CA

(831) 426-4738 (voice)
(831) 426-4748 (FAX)
Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)
Metadata extensions used:

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