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1700 Cascadia earthquake

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The 1700 Cascadia earthquake occurred along the Cascadia subduction zone on January 26, 1700, with an estimated moment magnitude of 8.7–9.2. The megathrust earthquake involved the Juan de Fuca plate from mid-Vancouver Island, south along the Pacific Northwest coast as far as northern California. The plate slipped an average of 20 meters (66 ft) along a fault rupture about 1,000 kilometers (620 miles) long.

1700 Cascadia earthquake
1700 Cascadia earthquake is located in North America
1700 Cascadia earthquake
USGS-ANSSComCat
Local dateJanuary 26, 1700; 324 years ago (1700-01-26)
Local timecirca 21:00 PST[1]
Magnitude8.7–9.2 Mw[2]
Epicenter45°N 125°W / 45°N 125°W / 45; -125[1]
FaultCascadia subduction zone
TypeMegathrust
TsunamiYes
CasualtiesMany Native Americans killed or displaced by shaking or subsequent tsunami

The earthquake caused a tsunami which struck the west coast of North America and the coast of Japan.[3] Japanese tsunami records, along with reconstructions of the wave moving across the ocean, put the earthquake at about 9:00 PM Pacific Time on the evening of 26 January 1700.[4]

Cascadia subduction zone
Sandsheet thought to have resulted from the tsunami caused by the 1700 earthquake, exposed on the bank of the Salmon River, Oregon

Evidence

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The earthquake took place at about 21:00 PT on January 26, 1700 (NS). Although there are no written records for the region from the time, the timing of the earthquake has been inferred from Japanese records of a tsunami that does not correlate with any other Pacific Rim quake. The Japanese records exist primarily in the modern-day Iwate Prefecture, in communities such as Tsugaruishi, Miyako (Kuwagasaki) and Ōtsuchi.[4]

Scientific research

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The most important clue linking the tsunami in Japan and the earthquake in the Pacific Northwest comes from studies of tree rings (dendrochronology), which show that several "ghost forests" of red cedar trees in Oregon and Washington, killed by lowering of coastal forests into the tidal zone by the earthquake, have outermost growth rings that formed in 1699, the last growing season before the tsunami.[5] This includes both inland stands of trees, such as one on the Copalis River in Washington,[5] and pockets of tree stumps that are now under the ocean surface and become exposed only at low tide.[6]

Sediment layers in these locations demonstrate a pattern consistent with seismic and tsunami events around this time.[7] Core samples from the ocean floor, as well as debris samples from some earthquake-induced landslides in the Pacific Northwest, also support this timing of the event.[6] Archaeological research in the region has uncovered evidence of several coastal villages having been flooded and abandoned around 1700.[8]

Cultural research

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The contemporary indigenous groups of Cascadia had no known written documentation like that of the Japanese tsunami, but numerous oral traditions describing a great earthquake and inundation exist among indigenous coastal peoples from British Columbia to Northern California.[5][9] These do not specify a date, and not all earthquake stories in the region can be ascribed to the 1700 quake; however, virtually all of the native peoples in the region have at least one traditional story of an event of unmatched destructive power.

Some of the stories contain temporal clues—such as a time estimate in generations since the event[8]—which suggest a date range in the late 1600s or early 1700s,[5] or which concur with the event's timing in other ways. For instance, the Huu-ay-aht legend of a large earthquake and ocean wave devastating their settlements at Pachena Bay places the event on a winter evening shortly after the village's residents had gone to sleep (consistent with the 9pm reconstructed time).[10] Every community on Pachena Bay was wiped out except for Masit on a mountainside 75 feet (23 m) above sea level.[11] The only other Panchena Bay survivor was a young woman named Anacla aq sop, who happened to be staying that day at Kiix-in, located on the less-tsunami-impacted Barkley Sound.

Kwakwaka'wakw (Kwakiutl) stories from the north end of Vancouver Island report a night-time earthquake that caused virtually all houses in their community to collapse;[8] Cowichan stories from Vancouver Island's inner coast speak of a nighttime earthquake, causing a landslide that buried an entire village.[8] Makah stories from Washington speak of a great night-time earthquake, of which the only survivors were those who immediately fled inland before the tsunami hit.[12] The Quileute people in Washington have a story about a flood so powerful that villagers in their canoes were swept inland all the way to Hood Canal.[13]

Ethnographic research has focused on a common regional pattern of art and mythology depicting a great battle between a thunderbird and a whale,[8] as well as cultural signifiers such as earthquake-inspired ritual masks and dances.[14]

Future threats

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Cascadia earthquake sources
 
A scenario of a magnitude 9.0 earthquake on the Cascadia subduction zone by the United States Geological Survey.

The geological record reveals that great earthquakes with moment magnitude 8 or higher occur in the Cascadia subduction zone about every 500 years on average, often accompanied by tsunamis. There is evidence of at least 13 events at intervals from about 300 to 900 years with an average of 570–590 years.[15]

As seen in the 1700 quake, the 2004 Indian Ocean earthquake, and the 2011 Tōhoku earthquake and tsunami, subduction zone earthquakes can cause large tsunamis, and many coastal areas in the region have prepared tsunami evacuation plans in anticipation of a possible future Cascadia earthquake. However, the major nearby cities, notably Seattle, Portland, Vancouver, Victoria, and Tacoma might be sheltered from the full brunt of a tsunami. These cities do have many vulnerable structures, especially bridges and unreinforced brick buildings; consequently, most of the damage to the cities would probably be from the earthquake itself. One expert asserts that buildings in Seattle are inadequate even to withstand an event of the size of the magnitude 7.9 1906 San Francisco earthquake, let alone a more powerful one.[16]

Kenneth Murphy, who directs FEMA's Region X, the division responsible for Oregon, Washington, Idaho, and Alaska, stated, "Our operating assumption is that everything west of Interstate 5 will be toast."[17]

Recent findings conclude that the Cascadia subduction zone is more complex and volatile than previously believed.[18] In 2010, geologists predicted a 37% chance of a magnitude 8.2+ event within 50 years, and a 10% to 15% chance that the entire Cascadia subduction zone will rupture with a magnitude 9+ event within the same time frame.[19][20] Geologists have also determined the Pacific Northwest is not prepared for such an earthquake. The tsunami produced could reach heights of 80 to 100 feet (24 to 30 m).[21]

A 2004 study revealed the potential for relative mean sea level rise (caused by subsidence of coastal land) along the Cascadia subduction zone. It postulated that cities on the west coast of Vancouver Island, such as Tofino and Ucluelet, are at risk for a 1-to-2-metre (3 ft 3 in to 6 ft 7 in) subsidence, relative to mean sea level.[22]

The confirmation of their oral traditions about a great earthquake has led many aboriginal groups in the area to initiate projects to relocate their coastal communities to higher and safer ground in preparation for the predicted next earthquake.[10] The Huu-ay-aht People have rebuilt their administration building on a high point in their territory;[10] coastal residents are immediately evacuated to this building whenever a tsunami warning is issued, as an interim measure toward eventually relocating all residents to higher ground.[23] The Quileute people secured a land grant from the US government in 2012 to move their settlement inland, both as protection from a future tsunami threat and because of more frequent flooding on the Quillayute River.[13] The Shoalwater Bay Indian Tribe also sought federal funding to move their community uphill receiving a FEMA PDM grant to build the first vertical evacuation tower on their coast, completed near the Tokeland Marina in 2022.[24][25]

In 2023, Washington scientists reported on a detailed study of a high-pressure and high-temperature seafloor seep, likely on the plate boundary, offshore of Oregon.[26] The first seep found on the CSZ, it has been named 'Pythia's Oasis', and may play a role in the regulation of overpressures.[27]

Some other subduction zones have major earthquakes every 100 to 200 years; the longer interval here may indicate unusually large stress buildup and subsequent unusually large earthquake slip.[28]

Bridge of the Gods – Bonneville Slide

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It was once conjectured that the Cascadia earthquake may also have been linked to the Bridge of the Gods – Bonneville Slide and the Tseax Cone eruption in British Columbia, Canada.[29] However, recent investigations using radiocarbon dating and dendrochronology date the Bonneville landslide around 1450.[30][31][32]

See also

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References

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  1. ^ a b National Geophysical Data Center / World Data Service (NGDC/WDS) (1972), Significant Earthquake Information (Data Set), National Geophysical Data Center, NOAA, doi:10.7289/V5TD9V7K
  2. ^ Atwater et al. 2005, p. 98
  3. ^ Atwater, B. F.; Musumi-Rokkaku, S.; Satake, K.; Yoshinobu, T.; Kazue, U.; Yamaguchi, D. K. (2005). The Orphan Tsunami of 1700 – Japanese Clues to a Parent Earthquake in North America. U.S. Geological Survey Professional Paper 1707. United States Geological Survey–University of Washington Press. ISBN 978-0-295-98535-0.
  4. ^ a b Kenji Satake; Kunihiko Shimazaki; Yoshinobu Tsuji; Kazue Ueda (18 January 1996). "Time and size of a giant earthquake in Cascadia inferred from Japanese tsunami records of January 1700". Nature. 379 (6562): 246–249. Bibcode:1996Natur.379..246S. doi:10.1038/379246a0. S2CID 8305522.
  5. ^ a b c d Kathryn Schulz (July 20, 2015). "The Really Big One". The New Yorker.
  6. ^ a b "Jan. 26, 1700: How Scientists Know When The Last Big Earthquake Happened Here". Oregon Public Broadcasting, January 26, 2015.
  7. ^ "Ghosts of Tsunamis Past" Archived 2018-08-28 at the Wayback Machine. American Museum of Natural History.
  8. ^ a b c d e Ruth S. Ludwin; Robert Dennis; Deborah Carver; Alan D. McMillan; Robert Losey; John Clague; Chris Jonientz-Trisler; Janine Bowechop; Jacilee Wray; Karen James (2005), "Dating the 1700 Cascadia Earthquake: Great Coastal Earthquakes in Native Stories" (PDF), Seismological Research Letters, 76 (2): 140–148, Bibcode:2005SeiRL..76..140L, doi:10.1785/gssrl.76.2.140, archived from the original (PDF) on 2015-07-24, retrieved 2015-07-24
  9. ^ "Tsunamis and Earthquakes – Native American Legends of Tsunamis in Pacific NW – USGS PCMSC".
  10. ^ a b c Meissner, Dirk (18 January 2015), "Earth will rip open like a zipper, expert says, when overdue Vancouver Island quake strikes", Toronto Star, retrieved 19 January 2015
  11. ^ "Prepare for next tsunami, says chief". Raven's Eye, Vol. 8, No. 9, 2009.
  12. ^ "Cascadia’s Locked Fault Means Massive Earthquake Is Due in Pacific Northwest: Seismologists" Archived 2015-07-31 at the Wayback Machine. Indian Country Today Media Network, December 16, 2014.
  13. ^ a b "Haida Gwaii Quake Brings Home the Importance of Quileute Relocation Legislation" Archived 2016-08-23 at the Wayback Machine. Indian Country Today Media Network, November 6, 2012.
  14. ^ "Get ready for the Big One". The Globe and Mail, April 22, 2011.
  15. ^ Witter, Robert C.; Kelsey, Harvey M.; Hemphill-Haley, Eileen (October 2003). "Great Cascadia earthquakes and tsunamis of the past 6700 years, Coquille River estuary, southern coastal Oregon". Geological Society of America Bulletin. 115 (10): 1289–1306. Bibcode:2003GSAB..115.1289W. doi:10.1130/b25189.1.
  16. ^ Yanev, Peter (27 March 2010). "Shake, Rattle, Seattle". The New York Times. p. WK11.
  17. ^ Schulz, Kathryn (20 July 2015). "The Really Big One". The New Yorker.
  18. ^ "A Major Earthquake in the Pacific Northwest Looks Even Likelier". The Atlantic. August 16, 2016.
  19. ^ "Odds Are 1-In-3 That A Huge Quake Will Hit Northwest in Next 50 Years". Oregon State University. 24 May 2010. Archived from the original on 27 May 2010. Retrieved 2010-05-24.
  20. ^ Oregon State University (May 25, 2010). "Odds are about 1-in-3 that mega-earthquake will hit Pacific Northwest in next 50 years, scientists say". ScienceDaily (Press release).
  21. ^ "Perilous Situation". The Oregonian. 2009-04-19. Archived from the original on 23 April 2009. Retrieved 2009-05-12.
  22. ^ Leonard, Lucinda J.; Hyndman, Roy D.; Mazzotti, Stéphane (2004). "Coseismic subsidence in the 1700 great Cascadia earthquake: Coastal estimates versus elastic dislocation models". GSA Bulletin. 116 (5–6): 655–670. Bibcode:2004GSAB..116..655L. doi:10.1130/B25369.1.
  23. ^ Munro, Margaret (March 8, 2012). "Monster earthquake threat looms over B.C. coastal communities". Vancouver Sun. Archived from the original on February 3, 2019. Retrieved January 27, 2019.
  24. ^ "Coastal Washington tribe creates higher ground by building tsunami tower, first of its type here". Oregon Public Broadcasting. 2022-08-08. Archived from the original on 10 February 2023. Retrieved 2023-02-10.
  25. ^ "Here's Where the U.S. Is Testing a New Response to Rising Seas". The New York Times. 2022-11-02. Archived from the original on 10 February 2023. Retrieved 2023-02-10.
  26. ^ Hickey, Hannah (10 Apr 2023). "Warm liquid spewing from Oregon seafloor comes from Cascadia fault, could offer clues to earthquake hazards". UW News. Retrieved 13 April 2023.
  27. ^ Brendan T. Philip (25 Jan 2023). "Fluid sources and overpressures within the central Cascadia Subduction Zone revealed by a warm, high-flux seafloor seep". Science Advances. 9 (4): eadd6688. Bibcode:2023SciA....9D6688P. doi:10.1126/sciadv.add6688. PMC 9876559. PMID 36696502.
  28. ^ "Cascadia Subduction Zone". Pacific Northwest Seismic Network.
  29. ^ Hill, Richard L. (2002-05-15). "Great Cascadia Earthquake Penrose Conference". The Oregonian. Archived from the original on 2008-10-24.
  30. ^ O'Connor, Jim E. (September 2004). "The Evolving Landscape of the Columbia River Gorge: Lewis and Clark and Cataclysms on the Columbia". Oregon Historical Quarterly. 105 (3): 390–421. doi:10.1353/ohq.2004.0043. S2CID 131976728. Archived from the original on 2009-03-28. Retrieved 2009-09-07.
  31. ^ Pringle, Patrick T. (2009). "The Bonneville slide" (PDF). Columbia Gorge Interpretive Center Museum Explorations (Fall-Winter 2009): 2–3. Archived from the original (PDF) on 2018-01-05. Retrieved 2012-02-03.
  32. ^ "10,000 years of Cascadia earthquakes". The Oregonian. Retrieved June 11, 2019.

Further reading

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General

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Native and Japanese accounts

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Current hazards

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