fbpx
Wikipedia

Seattle Fault

May 04, 2024

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.

Seattle Fault
The Seattle Fault cuts across Puget Sound and into Seattle itself. Restoration Point in the foreground, Alki Point is barely seen at the right edge of the picture.
EtymologySeattle
Coordinates47°36′36″N 122°19′59″W / 47.610°N 122.333°W / 47.610; -122.333
CountryUnited States
StateWashington
CitiesSeattle
Characteristics
Part ofPuget Sound faults
Length70 km (43 mi)
Tectonics
PlateNorth American
StatusActive
Earthquakesc. 900 CE
TypeThrust fault
MovementReverse
AgeEocene-recent (40-0 Ma)

Notable earthquake edit

See also: Lake Washington sunken forests

First suspected from mapping of gravitational anomalies in 1965[1] and an uplifted marine terrace at Restoration Point (foreground in picture above), the Seattle Fault's existence and likely hazard were definitively established by a set of five reports published in Science in 1992. These reports looked at the timing of abrupt uplift and subsidence around Restoration Point and Alki Point (distant right side of picture),[2] tsunami deposits on Puget Sound,[3] turbidity in lake paleosediments,[4] rock avalanches,[5] and multiple landslides around Lake Washington,[6] and determined that all these happened about 1100 years ago (between 900 and 930 CE[7]), and most likely due to an earthquake of magnitude 7 or greater on the Seattle Fault.

 
Representation of the a'yahos spirit.

Although the 900–930 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 Psai-Yah-hus near the Fauntleroy ferry dock in West Seattle.[8]

Geology edit

 
Approximate location of the Seattle Fault Zone (and other faults). The section of the fault zone directly under "Seattle" corresponds to the red line in the photo at the top. (DGER[9])
 
One model of the Seattle Uplift: Cross-section (south to north) along the east side of central Puget Sound, looking west. TB = Tacoma Basin EPZ = East Passage Zone (Maury Island), SFZ = Seattle Fault Zone (Alki Point). Grey dots are hypocenters of earthquakes of magnitude 2 or more for 1970–2001. (Fig. 17D from Johnson & others 2004)

The Seattle Fault is the structural boundary where 50–60 million years old (early Tertiary) basalt of the Crescent Formation on the south has been uplifted – the Seattle Uplift – and is tipping into the Seattle Basin, where the Tertiary bedrock is buried under at least 7 km (4.3 miles) of relatively softer, lighter sedimentary strata of the younger Blakeley and Blakely Harbor formations.[10] This has resulted in a 4 to 7 km (2.5 to 4.3 miles) wide zone of complex faulting, with three or more main south-dipping thrust faults.[11] Most of the faulting is "blind" (not reaching the surface), and generally difficult to locate because of heavy vegetation or development. Three principal strands have been identified, their location determined by high-resolution seismic reflection[12] and aeromagnetic surveys.[13] The northernmost strand lies nearly along Interstate 90 and then under Lake Sammamish.[14] The central section of the fault zone – where it crosses the apparent location of the Olympic–Wallowa Lineament – shows marked variation in the location of the strands and of the underlying structure, but the nature and significance of this is not understood.

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 Eocene).[23] This is about the time that the strike-slip movement on the north-striking Straight Creek Fault to the east ceased, due to the intrusions of plutons.[24] It appears that when the Straight Creek Fault became stuck the north–south compressive force that it had accommodated by strike-slip motion was transferred to the crust of the Puget Lowland, which subsequently folded and faulted, and the various blocks jammed over one another.

Other scarps associated with the Seattle fault have been identified by LIDAR-based mapping;[25] trenching has generally shown the faulting to be more complex than was first realized.[26] Many of the details of the Seattle Fault, including recurrence rate, remain to be resolved. A study of sediments in Lake Washington found evidence of seven large (M > 7) earthquakes in the last 3500 years.[27]

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 edit

 
Shipping-container crane at Port-au-Prince (Haiti) harbor leaning after earthquake-induced ground failure. Seattle's waterfront faces similar risk

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,[30] whereas a magnitude 9 subduction event would damage only around 87 bridges in all of Western Washington.[31] The same study also found that with failure of just six bridges (the minimum damage for a Benioff M 6.5 event) there could be at least $3 billion lost in business revenue alone.[32] Subsequent retrofitting by the Washington Department of Transportation and the City of Seattle would likely reduce damage to key bridges. But there is concern that such an earthquake on the Seattle Fault would devastate unreinforced masonry (URM) buildings, of which the City of Seattle is estimated to have around a thousand, concentrated in Capitol Hill, Pioneer Square, and the International District.[33]

 
Damage to a masonry building (Cadillac Hotel) in Seattle, from the 2001 Nisqually earthquake

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 paleoseismological studies show that the Seattle Fault can generate a very damaging magnitude 7.0 earthquake.[35] In addition to extensive damage to unreinforced structures and structures built on fill (such as much of Seattle's Pioneer Square area, the industrial area, and the waterfront), computer modeling has shown that such earthquakes could cause a tsunami of about 2 m (6 feet 7 inches) high on Elliott Bay.[36] The modeling shows that such a tsunami would also inundate the industrial areas on Commencement Bay 30 miles south (Tacoma) and low-lying areas on the Puyallup River delta.[37] There is also concern that a severe or prolonged event could cause failure of the Duwamish or Puyallup River deltas, where the main port facilities for Seattle and Tacoma are located (Harbor Island and Commencement Bay).[38]

See also edit

Notes edit

  1. ^ Danes & others 1965.
  2. ^ Bucknam & others 1992.
  3. ^ Atwater & Moore 1992.
  4. ^ Karlin & Abella 1992.
  5. ^ Schuster & others 1992.
  6. ^ Jacoby & others 1992.
  7. ^ Atwater 1999.
  8. ^ Ludwin & others 2005; Buerge 1985.
  9. ^ Excerpt from DGER Geological Map GM-52
  10. ^ Pratt & others 1997, p.27,471; Johnson & others 1994, p.72; Nelson & others 2003, p.1389.
  11. ^ QFFDB Fault 570
  12. ^ Johnson & others 1999.
  13. ^ Blakely & others 2002.
  14. ^ Blakely & others 2002, p.170.
  15. ^ Blakely & others 2002, p.170; QFFDB Fault 570.
  16. ^ Dragovich & others 2009, GM-73.
  17. ^ Blakely & others 2009, p.118; Liberty 2009.
  18. ^ Anderson & others 2008
  19. ^ Brocher & others 2001, p.13,558.
  20. ^ Pratt & others 1997, § 4.3 and figure 2.
  21. ^ Johnson & others 2004, § 72.
  22. ^ Kelsey & others 2008. See also Nelson & others 2003.
  23. ^ Pratt & others 1997, p.27,481; Blakely & others 2002, p.169.
  24. ^ Vance & Miller 1994; Tabor & others 1984, pp.26, 43.
  25. ^ Haugerud & others 2003.
  26. ^ Nelson & others 2003, p.1389.
  27. ^ Karlin & Abella 1992, p.1619; Karlin & others 2004.
  28. ^ Kelsey & others 2008, p.1588; Troost & Booth 2004.
  29. ^ Bucknam & others 1992, p. 1611; Fisher & others 2005, p. 8.
  30. ^ Ballantyne & others 2002, p.9.
  31. ^ 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.
  32. ^ Ballantyne & others 2002, p.11.
  33. ^ Swanson & Findlay 2007, "Executive Summary", § 2.1.3, and figure 2.
  34. ^ Kelsey & others 2008, p. 1596.
  35. ^ Bucknam & others 1992, p. 1613.
  36. ^ Koshimura & Mofjeld 2001, p. 872.
  37. ^ Walsh & others 2009.
  38. ^ Gonzalez & others 2003, § 3; Kayen & Barnhardt 2007.

Sources edit

  • 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, doi:10.1785/gssrl.70.2.190
  • 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, Bibcode:1992Sci...258.1614A, doi:10.1126/science.258.5088.1614, PMID 17742526, 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), (PDF), GSA Bulletin, 114 (2): 169–177, Bibcode:2002GSAB..114..169B, doi:10.1130/0016-7606(2002)114<0169:LSASOT>2.0.CO;2, 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, Bibcode:2009Geosp...5..105B, doi:10.1130/GES00196.1
  • 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, Bibcode:2001JGR...10613541B, doi:10.1029/2001JB000154
  • 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, Bibcode:1992Sci...258.1611B, doi:10.1126/science.258.5088.1611, PMID 17742525, 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, Bibcode:1965JGR....70.5573D, doi:10.1029/JZ070i022p05573
  • 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, doi:10.1130/1052-5173(2003)13<0004:HLTOTP>2.0.CO;2
  • 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, Bibcode:1992Sci...258.1621J, doi:10.1126/science.258.5088.1621, PMID 17742529, 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, Bibcode:2004Tecto..23.1011J, doi:10.1029/2003TC001507
  • 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, Bibcode:1999GSAB..111.1042J, doi:10.1130/0016-7606(1999)111<1042:ATOTSF>2.3.CO;2
  • 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, Bibcode:1994Geo....22...71J, doi:10.1130/0091-7613(1994)022<0071:OAEOTS>2.3.CO;2
  • 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, Bibcode:1992Sci...258.1617K, doi:10.1126/science.258.5088.1617, PMID 17742527, 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, Bibcode:2004GSAB..116...94K, 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, Bibcode:2008GSAB..120.1581K, 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, Bibcode:2005SeiRL..76..426L, doi:10.1785/gssrl.76.4.426
  • 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, Bibcode:2003GSAB..115.1388N, 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, Bibcode:1997JGR...10227469P, doi:10.1029/97JB01830
  • 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, Bibcode:1992Sci...258.1620S, doi:10.1126/science.258.5088.1620, PMID 17742528, 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, Bibcode:1984GSAB...95...26T, doi:10.1130/0016-7606(1984)95<26:AASOLA>2.0.CO;2
  • 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 edit

  • 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. Bibcode:2022BuSSA.112.2715M. doi:10.1785/0120220013. ISSN 0037-1106. S2CID 251698220.

External links edit

  • 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
  • , 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.

May 04, 2024
seattle, fault, zone, multiple, shallow, east, west, thrust, faults, that, cross, puget, sound, lowland, through, seattle, state, washington, vicinity, interstate, highway, first, recognized, significant, seismic, hazard, 1992, when, reports, showed, that, abo. 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 Seattle FaultThe Seattle Fault cuts across Puget Sound and into Seattle itself Restoration Point in the foreground Alki Point is barely seen at the right edge of the picture EtymologySeattleCoordinates47 36 36 N 122 19 59 W 47 610 N 122 333 W 47 610 122 333CountryUnited StatesStateWashingtonCitiesSeattleCharacteristicsPart ofPuget Sound faultsLength70 km 43 mi TectonicsPlateNorth AmericanStatusActiveEarthquakesc 900 CETypeThrust faultMovementReverseAgeEocene recent 40 0 Ma Contents 1 Notable earthquake 2 Geology 3 Hazard 4 See also 5 Notes 6 Sources 7 Further reading 8 External linksNotable earthquake editSee also Lake Washington sunken forests First suspected from mapping of gravitational anomalies in 1965 1 and an uplifted marine terrace at Restoration Point foreground in picture above the Seattle Fault s existence and likely hazard were definitively established by a set of five reports published in Science in 1992 These reports looked at the timing of abrupt uplift and subsidence around Restoration Point and Alki Point distant right side of picture 2 tsunami deposits on Puget Sound 3 turbidity in lake paleosediments 4 rock avalanches 5 and multiple landslides around Lake Washington 6 and determined that all these happened about 1100 years ago between 900 and 930 CE 7 and most likely due to an earthquake of magnitude 7 or greater on the Seattle Fault nbsp Representation of the a yahos spirit Although the 900 930 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 Psai Yah hus near the Fauntleroy ferry dock in West Seattle 8 Geology edit nbsp Approximate location of the Seattle Fault Zone and other faults The section of the fault zone directly under Seattle corresponds to the red line in the photo at the top DGER 9 nbsp One model of the Seattle Uplift Cross section south to north along the east side of central Puget Sound looking west TB Tacoma Basin EPZ East Passage Zone Maury Island SFZ Seattle Fault Zone Alki Point Grey dots are hypocenters of earthquakes of magnitude 2 or more for 1970 2001 Fig 17D from Johnson amp others 2004 The Seattle Fault is the structural boundary where 50 60 million years old early Tertiary basalt of the Crescent Formation on the south has been uplifted the Seattle Uplift and is tipping into the Seattle Basin where the Tertiary bedrock is buried under at least 7 km 4 3 miles of relatively softer lighter sedimentary strata of the younger Blakeley and Blakely Harbor formations 10 This has resulted in a 4 to 7 km 2 5 to 4 3 miles wide zone of complex faulting with three or more main south dipping thrust faults 11 Most of the faulting is blind not reaching the surface and generally difficult to locate because of heavy vegetation or development Three principal strands have been identified their location determined by high resolution seismic reflection 12 and aeromagnetic surveys 13 The northernmost strand lies nearly along Interstate 90 and then under Lake Sammamish 14 The central section of the fault zone where it crosses the apparent location of the Olympic Wallowa Lineament shows marked variation in the location of the strands and of the underlying structure but the nature and significance of this is not understood 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 Eocene 23 This is about the time that the strike slip movement on the north striking Straight Creek Fault to the east ceased due to the intrusions of plutons 24 It appears that when the Straight Creek Fault became stuck the north south compressive force that it had accommodated by strike slip motion was transferred to the crust of the Puget Lowland which subsequently folded and faulted and the various blocks jammed over one another Other scarps associated with the Seattle fault have been identified by LIDAR based mapping 25 trenching has generally shown the faulting to be more complex than was first realized 26 Many of the details of the Seattle Fault including recurrence rate remain to be resolved A study of sediments in Lake Washington found evidence of seven large M gt 7 earthquakes in the last 3500 years 27 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 edit nbsp Shipping container crane at Port au Prince Haiti harbor leaning after earthquake induced ground failure Seattle s waterfront faces similar risk 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 30 whereas a magnitude 9 subduction event would damage only around 87 bridges in all of Western Washington 31 The same study also found that with failure of just six bridges the minimum damage for a Benioff M 6 5 event there could be at least 3 billion lost in business revenue alone 32 Subsequent retrofitting by the Washington Department of Transportation and the City of Seattle would likely reduce damage to key bridges But there is concern that such an earthquake on the Seattle Fault would devastate unreinforced masonry URM buildings of which the City of Seattle is estimated to have around a thousand concentrated in Capitol Hill Pioneer Square and the International District 33 nbsp Damage to a masonry building Cadillac Hotel in Seattle from the 2001 Nisqually earthquake 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 paleoseismological studies show that the Seattle Fault can generate a very damaging magnitude 7 0 earthquake 35 In addition to extensive damage to unreinforced structures and structures built on fill such as much of Seattle s Pioneer Square area the industrial area and the waterfront computer modeling has shown that such earthquakes could cause a tsunami of about 2 m 6 feet 7 inches high on Elliott Bay 36 The modeling shows that such a tsunami would also inundate the industrial areas on Commencement Bay 30 miles south Tacoma and low lying areas on the Puyallup River delta 37 There is also concern that a severe or prolonged event could cause failure of the Duwamish or Puyallup River deltas where the main port facilities for Seattle and Tacoma are located Harbor Island and Commencement Bay 38 See also editGeology of the Pacific Northwest Tacoma FaultNotes edit Danes amp others 1965 Bucknam amp others 1992 Atwater amp Moore 1992 Karlin amp Abella 1992 Schuster amp others 1992 Jacoby amp others 1992 Atwater 1999 Ludwin amp others 2005 Buerge 1985 Excerpt from DGER Geological Map GM 52 Pratt amp others 1997 p 27 471 Johnson amp others 1994 p 72 Nelson amp others 2003 p 1389 QFFDB Fault 570 Johnson amp others 1999 Blakely amp others 2002 Blakely amp others 2002 p 170 Blakely amp others 2002 p 170 QFFDB Fault 570 Dragovich amp others 2009 GM 73 Blakely amp others 2009 p 118 Liberty 2009 Anderson amp others 2008 Brocher amp others 2001 p 13 558 Pratt amp others 1997 4 3 and figure 2 Johnson amp others 2004 72 Kelsey amp others 2008 See also Nelson amp others 2003 Pratt amp others 1997 p 27 481 Blakely amp others 2002 p 169 Vance amp Miller 1994 Tabor amp others 1984 pp 26 43 Haugerud amp others 2003 Nelson amp others 2003 p 1389 Karlin amp Abella 1992 p 1619 Karlin amp others 2004 Kelsey amp others 2008 p 1588 Troost amp Booth 2004 Bucknam amp others 1992 p 1611 Fisher amp others 2005 p 8 Ballantyne amp 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 amp others 2002 p 11 Swanson amp Findlay 2007 Executive Summary 2 1 3 and figure 2 Kelsey amp others 2008 p 1596 Bucknam amp others 1992 p 1613 Koshimura amp Mofjeld 2001 p 872 Walsh amp others 2009 Gonzalez amp others 2003 3 Kayen amp Barnhardt 2007 Sources editAnderson 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 doi 10 1785 gssrl 70 2 190 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 Bibcode 1992Sci 258 1614A doi 10 1126 science 258 5088 1614 PMID 17742526 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 Bibcode 2002GSAB 114 169B doi 10 1130 0016 7606 2002 114 lt 0169 LSASOT gt 2 0 CO 2 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 Bibcode 2009Geosp 5 105B doi 10 1130 GES00196 1 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 Bibcode 2001JGR 10613541B doi 10 1029 2001JB000154 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 Bibcode 1992Sci 258 1611B doi 10 1126 science 258 5088 1611 PMID 17742525 S2CID 39423769 Buerge D M March 6 13 1985 Lost Seattle our shameful neglect of a rich archeological past Seattle Weekly Danes 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 Bibcode 1965JGR 70 5573D doi 10 1029 JZ070i022p05573 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 Gonzalez 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 doi 10 1130 1052 5173 2003 13 lt 0004 HLTOTP gt 2 0 CO 2 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 Bibcode 1992Sci 258 1621J doi 10 1126 science 258 5088 1621 PMID 17742529 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 Bibcode 2004Tecto 23 1011J doi 10 1029 2003TC001507 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 Bibcode 1999GSAB 111 1042J doi 10 1130 0016 7606 1999 111 lt 1042 ATOTSF gt 2 3 CO 2 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 Bibcode 1994Geo 22 71J doi 10 1130 0091 7613 1994 022 lt 0071 OAEOTS gt 2 3 CO 2 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 Bibcode 1992Sci 258 1617K doi 10 1126 science 258 5088 1617 PMID 17742527 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 Bibcode 2004GSAB 116 94K 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 Bibcode 2008GSAB 120 1581K 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 Bibcode 2005SeiRL 76 426L doi 10 1785 gssrl 76 4 426 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 Bibcode 2003GSAB 115 1388N 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 Bibcode 1997JGR 10227469P doi 10 1029 97JB01830 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 Bibcode 1992Sci 258 1620S doi 10 1126 science 258 5088 1620 PMID 17742528 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 Bibcode 1984GSAB 95 26T doi 10 1130 0016 7606 1984 95 lt 26 AASOLA gt 2 0 CO 2 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 Gonzalez 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 9Further reading editMoore 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 Bibcode 2022BuSSA 112 2715M doi 10 1785 0120220013 ISSN 0037 1106 S2CID 251698220 External links editUSGS 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 Retrieved from https en wikipedia org w index php title Seattle Fault amp oldid 1198106861, wikipedia, wiki, book, books, library,

article

, read, download, free, free download, mp3, video, mp4, 3gp, jpg, jpeg, gif, png, picture, music, song, movie, book, game, games.