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Cascadia tsunami deposit database

Dates

Publication Date
Start Date
1987
End Date
2002
File Modification Date
2013-05-16 14:07:18

Summary

The Cascadia Tsunami Deposit Database contains data on thelocation and sedimentological properties of tsunami depositsfound along the Cascadia margin. Data have been compiled from52 studies, documenting 59 sites from northern California toVancouver Island, British Columbia that contain known orpotential tsunami deposits. Bibliographical references areprovided for all sites included in the database. Cascadiatsunami deposits are usually seen as anomalous sand layers incoastal marsh or lake sediments. The studies cited in thedatabase use numerous criteria based on sedimentarycharacteristics to distinguish tsunami deposits from sandlayers deposited by other processes, such as river floodingand storm surges. Several studies cited in the [...]

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Purpose

The Cascadia Tsunami Deposit Database is acompilation of published data on the location and sedimentarycharacteristics of tsunami deposits found along the Cascadiamargin. It consolidates data from the earliest publishedreports on Cascadia tsunami deposits (e.g. Atwater, 1987,Reinhart and Bourgeois, 1987) to studies published or inpress by the year 2002. This database and associated reportis intended as a guide to the sedimentary features thatcharacterize Cascadia tsunami deposits and to the locationswhere tsunami deposits have been found along the Cascadiamargin. It also provides references for all of the tsunamideposits cited. The Cascadia Subduction Zone (CSZ) issituated off of the Pacific Northwest coast of North America,from Northern California to Vancouver Island, BritishColumbia (Figure 1). Great earthquakes (m > 8.0) onsubduction zones have the potential to trigger largetsunamis. While not all subduction zones generate greatearthquakes, it is believed that the CSZ has the potential togenerate great earthquakes. The CSZ shares many features withother subduction zones that experience great earthquakes (Heaton and Kanamori, 1984). Geologic evidence for greatearthquakes along the CSZ include turbidites off the Cascadiamargin (Adams, 1990) and stratigraphic evidence of suddencoastal subsidence (e.g. Atwater et al., 1995, Nelson andPeronius, 1996). Although no great earthquakes have occurredon the CSZ since European colonization of the PacificNorthwest in the mid 1800s, an Indian oral tradition from thePacific Northwest predating written records alludes to greatshaking of the earth and coastal flooding (Heaton andSnavely, 1985, Clague, 1995). Geologic evidence for largetsunamis along the Cascadia margin has only recently beenrecognized. Atwater (1987) published a report attributinganomalous sand layers in marsh sediments from southerncoastal Washington to tsunamis generated by great earthquakeson the CSZ. Since this time, more than 50 studies have beenpublished, documenting numerous sites containing confirmed orpotential tsunami deposits and detailing depositcharacteristics along the Pacific Northwest coast fromNorthern California to Vancouver Island, British Columbia (Figure 2). This rapid increase in our knowledge of Cascadiatsunami deposits has led to a greater public awareness oftsunami hazards, and improved our ability to assess the riskfrom future tsunamis. Data from tsunami deposits have beenincluded on tsunami inundation maps (e.g. Walsh et al.,2000). Tsunami deposits are a key component to therecognition and mitigation of tsunami hazards in the PacificNorthwest.
ArcExplorer screen capture showing distribution of catalogedtsunami deposits from this database along with geographicreference layers showing coastlines, topography, and politicalboundaries, 750x554 pixels, 202k bytes
ArcExplorer screen capture showing distribution of catalogedtsunami deposits from this database along with geographicreference layers showing coastlines, topography, and politicalboundaries, 750x554 pixels, 202k bytes

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