Seattle Fault
Seattle Fault | |
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The Seattle Fault is a zone of multiple shallow east–west thrust faults that cross the Puget Sound Lowland and through Seattle (in the U.S. state of Washington) in the vicinity of Interstate Highway 90. The Seattle Fault was first recognized as a significant seismic hazard in 1992, when a set of reports showed that about 1,100 years ago it was the scene of a major earthquake of about magnitude 7 – an event that entered Native American oral traditions. Extensive research has since shown the Seattle Fault to be part of a regional system of faults.
Notable earthquake
First suspected from mapping of gravitational anomalies in 1965
Although the 923-924 CE earthquake was over a thousand years ago, local Traditional Stories have preserved an association of a powerful supernatural spirit – a'yahos, noted for shaking, rushes of water, and landsliding – with five locales along the trace of the Seattle Fault, including a "spirit boulder" called
Geology
The Seattle Fault is the structural boundary where 50–60 million years old (early
The fault extends for approximately 70 km (43 miles)[15] from near Fall City on the east, where it appears to be terminated by the South Whidbey Island Fault,[16] to Hood Canal on the west[17] (not shown on the map). However, boundaries defining the western termination zone is currently unclear (see Puget Sound faults#Question of western termination[18]). It is the northern edge of the Seattle Uplift, of which the Tacoma Fault is the southern edge. One model has the Seattle and Tacoma faults converging at depth to form a wedge, which is being popped up by approximately north–south oriented compression that ultimately derives from plate tectonics.[19] Another model (see diagram) interprets the Seattle Uplift as a sheet of rock that is being forced up a ramp.[20] Subsequent work suggests that the structure of the Seattle Fault may vary from east to west, with both models being applicable in different sections.[21] A later model has part of the north-thrusting sheet forming a wedge between the sedimentary formations of the Seattle Basin and the underlying bedrock.[22]
The Seattle Fault is believed to date from about 40 million years ago (late
Other scarps associated with the Seattle fault have been identified by
Surface scarps due to faulting are rarely observed in this area (due to topography, vegetation, and urbanization); a rare exception can be seen at Mee Kwa Mooks Park south of Alki Point. This is the site of the West Seattle Fault; the prominent rise there is due to uplift on the north side of the fault.[28]
Hazard
The Seattle Fault (and the related Tacoma Fault) is not the only source of earthquake hazard in the Puget Lowland. Other faults in the near surface continental crust, such as the South Whidbey Island Fault (near Everett), and the yet to be studied Olympia Fault (near Olympia), though historically quiescent, are suspected of generating earthquakes of around magnitude 7. Others, such as the 2001 Nisqually earthquake, originate about 50 to 60 km (31 to 37 miles) below Puget Sound in the Benioff zone of the subducting Juan de Fuca Plate; being so deep their energy is dissipated. And there are the infrequent but very powerful great subduction events, such as the magnitude 9 1700 Cascadia earthquake, where the entire Cascadia subduction zone, from Cape Mendocino to Vancouver Island, slips.[29]
But the Seattle and Tacoma faults are probably the most serious earthquake threat to the populous Seattle–Tacoma area. A 2002 study of bridge vulnerability estimated that a magnitude 7 earthquake on the Seattle Fault would damage approximately 80 bridges in the Seattle–Tacoma area,
Other recent work[34] indicates that the Seattle Fault can generate two types of earthquakes; both pose "considerable hazard" to the Seattle metropolitan region. The A.D. 900–930 earthquake is believed to be the only instance in the past 7,000 years of the type that causes a regional uplift. The other type is more localized and shallower (and therefore more damaging); at least four such events are believed to have occurred in the past 3,000 years on the west end of the fault. (The history of the central and eastern segments is not known.)
Calculations based on fault length and
See also
Notes
- ^ Danes & others 1965.
- ^ Bucknam & others 1992.
- ^ Atwater & Moore 1992.
- ^ Karlin & Abella 1992.
- ^ Schuster & others 1992.
- ^ Jacoby & others 1992.
- ^ https://www.science.org/doi/10.1126/sciadv.adh4973?adobe_mc=MCMID%3D06292276686449277044143600107531816595%7CMCORGID%3D242B6472541199F70A4C98A6%2540AdobeOrg%7CTS%3D1695670174)
- ^ Ludwin & others 2005; Buerge 1985.
- ^ Excerpt from DGER Geological Map GM-52
- ^ Pratt & others 1997, p.27,471; Johnson & others 1994, p.72; Nelson & others 2003, p.1389.
- ^ QFFDB Fault 570
- ^ Johnson & others 1999.
- ^ Blakely & others 2002.
- ^ Blakely & others 2002, p.170.
- ^ Blakely & others 2002, p.170; QFFDB Fault 570.
- ^ Dragovich & others 2009, GM-73.
- ^ Blakely & others 2009, p.118; Liberty 2009.
- ^ Anderson & others 2008
- ^ Brocher & others 2001, p.13,558.
- ^ Pratt & others 1997, § 4.3 and figure 2.
- ^ Johnson & others 2004, § 72.
- ^ Kelsey & others 2008. See also Nelson & others 2003.
- ^ Pratt & others 1997, p.27,481; Blakely & others 2002, p.169.
- ^ Vance & Miller 1994; Tabor & others 1984, pp.26, 43.
- ^ Haugerud & others 2003.
- ^ Nelson & others 2003, p.1389.
- ^ Karlin & Abella 1992, p.1619; Karlin & others 2004.
- ^ Kelsey & others 2008, p.1588; Troost & Booth 2004.
- ^ Bucknam & others 1992, p. 1611; Fisher & others 2005, p. 8.
- ^ Ballantyne & others 2002, p.9.
- ^ The much greater energy of subduction earthquake is spread out over a larger area, and concentrated mainly on the coast, where there is less development.
- ^ Ballantyne & others 2002, p.11.
- ^ Swanson & Findlay 2007, "Executive Summary", § 2.1.3, and figure 2.
- ^ Kelsey & others 2008, p. 1596.
- ^ Bucknam & others 1992, p. 1613.
- ^ Koshimura & Mofjeld 2001, p. 872.
- ^ Walsh & others 2009.
- ^ Gonzalez & others 2003, § 3; Kayen & Barnhardt 2007.
Sources
- Anderson, M. L.; Dragovich, J. D.; Blakely, R. J.; Wells, R.; Brocher, T. M. (2008), "Where Does the Seattle Fault End? Structural Links and Kinematic Implications [Abstract #T23B-2022]", American Geophysical Union Fall Meeting 2008, Bibcode:2008AGUFM.T23B2022A, abstract #T23B-2022
- Atwater, B. F. (1999), "Radiocarbon dating of a Seattle earthquake to A.D. 900–930.", Seismological Research Letters, 70: 232,
- Atwater, B. F.; Moore, A. L. (4 December 1992), "A Tsunami About 1000 Years Ago in Puget Sound, Washington" (PDF), Science, 258 (5088): 1614–1617, S2CID 34602506
- Ballantyne, D.; Pierepiekarz, M.; Chang, S. (2002), Seismic Vulnerability Assessment of the Seattle–Tacoma Highway Corridor using HAZUS (PDF)
- Blakely, R. J.; Wells, R. E.; Weaver, C. S.; Johnson, S. Y. (February 2002), "Location, structure, and seismicity of the Seattle fault zone, Washington: Evidence from aeromagnetic anomalies, geologic mapping, and seismic-reflection data" (PDF), GSA Bulletin, 114 (2): 169–177, S2CID 128977256, archived from the original(PDF) on 2019-10-21
- Blakely, R. J.; Sherrod, B. L.; Hughes, J. F.; Anderson, M. L.; Wells, R. E.; Weaver, C. S. (2009), "The Saddle Mountain Fault Deformation Zone, Olympic Peninsula, Washington: Western Boundary of the Seattle Uplift" (PDF), Geosphere, 5 (2): 105–125,
- Brocher, T. M.; Parsons, T.; Blakely, R. J.; Christensen, N. I.; Fisher, M. A.; Wells, R. E.; the SHIPS Working Group (10 July 2001), "Upper crustal structure in Puget Lowland, Washington: Results from the 1998 Seismic Hazards Investigation in Puget Sound" (PDF), Journal of Geophysical Research, 106 (B7): 13, 541–13, 564,
- Brown, E. H.; Dragovich, J. D. (December 2003), "Tectonic elements and evolution of northwest Washington", Washington Division of Geology and Earth Resources, Geologic Map GM–52, 1 sheet, scale 1:625,000, 12 p. text
- Bucknam, R. C.; Hemphill-Haley, E.; Leopold, E. B. (4 December 1992), "Abrupt Uplift Within the Past 1700 Years at Southern Puget Sound, Washington" (PDF), Science, 258: 1611–1614, S2CID 39423769
- Buerge, D. M. (March 6–13, 1985), "Lost Seattle, our shameful neglect of a rich archeological past", Seattle Weekly
- Daneš, Z. F.; Bonno, M. M.; Brau, E.; Gilham, W. D.; Hoffman, T. T.; Johansen, D.; Jones, M. H.; Malfait, B.; Masten, J.; Teague, G. O. (15 November 1965), "Geophysical investigation of the Southern Puget Sound area, Washington", Journal of Geophysical Research, 70 (22): 5573–5580,
- Dragovich, J. D.; Walsh, T. J.; Anderson, M. L.; Hartog, R.; DuFrane, S. A.; Vervoot, J.; Williams, S. A.; Cakir, R.; Stanton, K. D.; Wolff, F. E.; Norman, D. K.; Czajkowski, J. L. (2009), "Geologic map of the North Bend 7.5-minute quadrangle, King County, Washington", Washington Division of Geology and Earth Resources, Geological Map GM–73, 1 sheet, scale 1:24,000, 39 p. text
- Fisher, M. A.; Hyndman, R. D.; Johnson, S. Y.; Brocher, T. M.; Crosson, R. S.; Wells, R. A.; Calvert, A. J.; ten Brink, U. S. (2005), "Crustal Structure and Earthquake Hazards of the Subduction Zone in Southwestern British Columbia and Western Washington" (PDF), U. S. Geological Survey, Professional Paper 1661-C
- González, F. I.; Sherrod, B. L.; Atwater, B. F.; Frankel, A. P.; Palmer, S. P.; Holmes, M. L.; Karlin, R. E.; Jaffe, B. E.; Titov, V. V.; Mofjeld, H. O.; Venturato, A. J. (June 2003), "Puget Sound Tsunami Sources – 2002 Workshop Report" (PDF), NOAA
- Haugerud, R. A.; Harding, D. J.; Johnson, S. Y.; Harless, J. L.; Weaver, C. S.; Sherrod, B. L. (June 2003), "High-Resolution Lidar Topography of the Puget Lowland, Washington – A Bonanza for Earth Science" (PDF), GSA Today, 13 (6): 4–10,
- Jacoby, G. C.; Williams, P. L.; Buckley, B. M. (4 December 1992), "Tree Ring Correlation Between Prehistoric Landslides and Abrupt Tectonic Events in Seattle, Washington", Science, 258: 1621–1623, S2CID 35721127
- Johnson, S. Y.; Blakely, R. J.; Stephenson, W. J.; Dadisman, S. V.; Fisher, M. A. (2004), "Active shortening of the Cascadia forearc and implications for seismic hazards of the Puget Lowland" (PDF), Tectonics, 23 (TC1011): 1–27,
- Johnson, S. Y.; Blakely, R. J.; Brocher, T. M.; Bucknam, R. C.; Haeussler, P. J.; Pratt, T. L.; Nelson, A. R.; Sherrod, B. L.; Wells, R.E.; Lidke, D.J.; Harding, D.J.; Kelsey, H.M. (2004), "Fault number 570, Seattle fault zone", in U.S. Geological Survey (ed.), Quaternary fault and fold database for the United States
- Johnson, S. Y.; Dadisman, S. V.; Childs, J. R.; Stanley, W. D. (July 1999), "Active Tectonics of the Seattle Fault and Central Puget Sound, Washington: Implications for earthquake hazards", GSA Bulletin, 111 (7): 1042–1053,
- Johnson, S. Y.; Potter, C. J.; Armentrout, J. M. (January 1994), "Origin and evolution of the Seattle Fault and Seattle Basin, Washington", Geology, 22 (1): 71–74,
- Karlin, R. E.; Abella, S. E. B. (4 December 1992), "Paleoearthquakes in the Puget Sound Region Recorded in Sediments from Lake Washington, U.S." (PDF), Science, 258: 1617–1620, S2CID 8354010
- Karlin, R. E.; Holmes, M.; Abella, S. E. B.; Sylvester, R. (February 2004), "Holocene landslides and a 3500-year record of Pacific Northwest earthquakes from sediments in Lake Washington", GSA Bulletin, 116 (1–2): 94–108, doi:10.1130/B25158.1
- Kayen, R. E.; Barnhardt, W. A. (2007), "Seismic stability of the Duwamish River delta, Seattle, Washington", U. S. Geological Survey, Professional Paper 1661-E
- Kelsey, H. M.; Sherrod, B. L.; Nelson, A. R.; Brocher, T. M. (November–December 2008), "Earthquakes generated from bedding plane-parallel reverse faults above an active wedge thrust, Seattle fault zone.", GSA Bulletin, 120 (11/12): 1581–1597, doi:10.1130/B26282.1
- Koshimura, S.; Mofjeld, H. O. (2001), "Inundation modeling of local tsunamis in Puget Sound, Washington, due to potential earthquakes", ITS 2001 Proceedings (Session 7, Number 7–18): 861–873
- Liberty, L. M. (2009), "The western extension of the Seattle fault: new insights from seismic reflection data" (PDF), U.S. Geological Survey, NEHRP, Project Award Number 08HQGR0075
- Ludwin, R. S.; Thrush, C. P.; Buerge, D.; Jonientz-Trisler, C.; Rasmussen, J.; Troost, K.; de los Angeles, A. (July–August 2005), "Serpent Spirit-power Stories along the Seattle Fault" (PDF), Seismological Research Letters, 76 (4): 426–431,
- Nelson, A. R.; Johnson, S. Y.; Kelsey, H. M.; Wells, R. E.; Sherrod, B. L.; Pezzopane, S. K.; Bradley, L.; Koehler, R. D.; Bucknam, R. C. (November 2003), "Late Holocene earthquakes on the Toe Jam Hill fault, Seattle fault zone, Bainbridge Island, Washington" (PDF), GSA Bulletin, 115 (11): 1368–1403, doi:10.1130/B25262.1
- Pratt, T. L.; Johnson, S. Y.; Potter, C. J.; Stephenson, W. J. (10 December 1997), "Seismic reflection images beneath Puget Sound, western Washington State: The Puget Lowland thrust sheet hypothesis" (PDF), Journal of Geophysical Research, 102 (B12): 27, 469–27, 490,
- Schuster, R. L.; Logan, R. L.; Pringle, P. T. (4 December 1992), "Prehistoric Rock Avalanches in the Olympic Mountains, Washington" (PDF), Science, 258: 1620–1621, S2CID 34847168
- Swanson, D. B.; Findlay, A. (December 2007), "City of Seattle Unreinforced Masonry Building Seismic Hazards Study" (PDF), City of Seattle Department of Planning and Development
- Tabor, R. W.; Frizzell, V. A. Jr.; Vance, J. A.; Naeser, C. W. (January 1984), "Ages and stratigraphy of lower and middle Tertiary sedimentary and volcanic rocks of the central Cascades, Washington: Application to the tectonic history of the Straight Creek fault", GSA Bulletin, 95 (1): 26–44,
- Troost, K. G.; Booth, D. B. (May 22, 2004), Geology of Seattle: City of Seattle Field Trip (PDF), Seattle-Area Geologic Mapping Project Department of Earth and Space Sciences University of Washington
- Vance, J. A.; Miller, R. B. (1994), "Another look at the Fraser River-Straight Creek Fault (FRSCF) [abstract]", Geological Society of America 1994 Annual Meeting, Abstracts with Programs, 24: 88
- Walsh, T. J.; Arcas, D.; Venturato, A. J.; Titov, V. V.; Mofjeld, H. O.; Chamberlin, C. C.; González, F. I. (July 2009), "Tsunami hazard map of Tacoma, Washington—Model results for Seattle fault and Tacoma fault earthquake tsunamis" (PDF), Washington Division of Geology and Earth Resources, Open File Report 2009-9
Further reading
- Moore, G. L.; Roland, E.; Bennett, S. E. K.; Watt, J.; Kluesner, J.; Brothers, D.; Myers, E. (2022). "High-Resolution Marine Seismic Imaging of the Seattle Fault Zone: Near-Surface Insights into Fault Zone Geometry, Quaternary Deformation, and Long-Term Evolution". Bulletin of the Seismological Society of America. 112 (5): 2715–2744. S2CID 251698220.
External links
- USGS Professional Paper 1560: Assessing Earthquake Hazards and Reducing Risk in the Pacific Northwest Technical, but readable. And has many good pictures.
- USGS: Reducing Earthquake Hazards in the Pacific Northwest
- USGS: Earthquake ground motion movies
- "Pinpointing devastation if Seattle Fault ruptures", Seattle Times, 2005-02-20, archived from the original on 2005-02-22, retrieved 2019-01-15
- Scenario for a Magnitude 6.7 Earthquake on the Seattle Fault Vivid and comprehensive.
- Washington State's Bridge Seismic Retrofit Program
- Earthquake Study: Four Vashon-Specific Scenarios Considerations for all islands.
- Puget Sound Tsunami Inundation Modeling (NOAA)
- Elliott Bay inundation map (DNR)
- Tsunami Hazard Map of the Elliott Bay Area (NOAA)
- Additional inundation maps (DNR Publications)
- Puget Sound Lidar Consortium Use of Lidar for locating faults.