Open main menu
Home
Random
Recent changes
Special pages
Community portal
Preferences
About Wikipedia
Disclaimers
Incubator escapee wiki
Search
User menu
Talk
Dark mode
Contributions
Create account
Log in
Editing
Cascadia subduction zone
Warning:
You are not logged in. Your IP address will be publicly visible if you make any edits. If you
log in
or
create an account
, your edits will be attributed to your username, along with other benefits.
Anti-spam check. Do
not
fill this in!
{{Short description|Convergent plate boundary that stretches from northern Vancouver Island to Northern California}} {{multiple image | align = right | image1 = Cascadia Subduction Zone.jpg | image2 = 9.0 Cascadia scenario (median).pdf | footer = Area of the Cascadia subduction zone (left) and a USGS scenario ShakeMap for a Mw9.0 event }} {{Coord|45|-124|type:landmark_region:US_dim:500km|display=title}} The '''Cascadia subduction zone''' is a {{cvt|960|km}} [[convergent boundary|convergent]] [[plate boundary]], about {{cvt|70|-|100|mi|-2|order=flip}} off the Pacific coast of North America, that stretches from northern [[Vancouver Island]] in [[Canada]] to [[Northern California]] in the United States. It is capable of producing 9.0+ [[Moment magnitude scale|magnitude]] earthquakes and [[tsunami]]s that could reach 30 m (100 ft) high. The Oregon Department of Emergency Management estimates shaking would last 5–7 minutes along the coast, with strength and intensity decreasing further from the epicenter.<ref>{{cite web | url=https://www.oregon.gov/oem/hazardsprep/pages/cascadia-subduction-zone.aspx | title=Oregon Department of Emergency Management : Cascadia Subduction Zone : Hazards and Preparedness : State of Oregon }}</ref> It is a very long, sloping [[subduction]] zone where the [[Explorer plate|Explorer]], [[Juan de Fuca plate|Juan de Fuca]], and [[Gorda plate|Gorda]] plates move to the east and slide below the much larger mostly continental [[North American plate]]. The zone varies in width and lies offshore beginning near [[Cape Mendocino]], Northern California, passing through [[Oregon]] and [[Washington (state)|Washington]], and terminating in Canada at about [[Vancouver Island]] in [[British Columbia]].<ref name="Schulz2015" /> The Explorer, Juan de Fuca, and Gorda plates are some of the remnants of the vast ancient [[Farallon plate]] which is now mostly subducted under the North American plate. The North American plate itself is moving slowly in a generally southwest direction, sliding over the smaller plates as well as the huge oceanic [[Pacific plate]] (which is moving in a northwest direction) in other locations such as the [[San Andreas Fault]] in central and southern California. Tectonic processes active in the Cascadia subduction zone region include [[Accretion (geology)|accretion]], [[subduction]], deep [[earthquake]]s, and active [[volcanism]] of the [[Cascade Volcanoes|Cascades]]. This volcanism has included such notable eruptions as [[Mount Mazama]] ([[Crater Lake]]) about 7,500 years ago, the [[Mount Meager massif]] ([[Bridge River Vent]]) about 2,350 years ago, and [[Mount St. Helens]] in 1980.<ref name="emporia.edu">{{cite web|url=http://www.emporia.edu/earthsci/student/geller2/cascadia.html |title=Cascadia Subduction Zone Volcanism in British Columbia |access-date=2008-12-18 |url-status=dead |archive-url=https://web.archive.org/web/20100602050632/http://www.emporia.edu/earthsci/student/geller2/cascadia.html |archive-date=2010-06-02 }} USGS</ref> Major cities affected by a disturbance in this subduction zone include [[Vancouver]] and [[Victoria, British Columbia]]; [[Seattle]], Washington; and [[Portland, Oregon]]. ==History== ===Tradition=== {{Main|Thunderbird and Whale}} There are no contemporaneous written records of the [[1700 Cascadia earthquake]]. Orally transmitted legends from the [[Olympic Peninsula]] area tell of [[Thunderbird and Whale|an epic battle between a thunderbird and a whale]]. In 2005, seismologist Ruth Ludwin set out to collect and analyze anecdotes from various [[Native Americans in the United States|First Nations]] groups. Reports from the [[Huu-ay-aht First Nations|Huu-ay-aht]],<ref name=NatGeo/> [[Makah]],<ref name=NatGeo/> [[Hoh Indian Tribe of the Hoh Indian Reservation|Hoh]],<ref name=AMNH/> [[Quileute]],<ref name=Smithsonian/><ref name=AMNH/> [[Yurok people|Yurok]],<ref name=Smithsonian/> and [[Duwamish tribe|Duwamish]]<ref name=Smithsonian/> peoples referred to earthquakes and saltwater floods. This collection of data allowed the researchers to come up with an estimated date range for the event; the midpoint was in the year 1701.<ref name=NatGeo/> ===Ghost forests=== [[File:Neskowin Ghost Forest - 2016.jpg|thumb|Stumps of trees at the Neskowin Ghost Forest]] [[File:Neskowin Ghost Forest Stump Close Up.jpg|thumb|Large tree stump protruding from beach sand]] During low tide one day in March 1986, paleogeologist [[Brian Atwater]] dug along [[Neah Bay]] with a ''nejiri gama'', a small hand hoe. Under a top layer of sand, he uncovered a distinct plant—[[arrowgrass]]—that had grown in a layer of marsh soil. This finding was evidence that the ground had suddenly sunk under sea level, causing saltwater to kill the vegetation. The event had happened so quickly that the top layer of sand sealed away the air, thus preserving centuries-old plants.<ref name = Discover/> In 1987, Atwater mounted another expedition paddling up the [[Copalis River]] with Dr. David Yamaguchi, who was then studying the eruptions of [[Mount St. Helens]].<ref name = Discover/> The pair happened upon a section of "[[ghost forest]]", so-called due to the dead, gray stumps left standing after a sudden inundation of salt water had killed them hundreds of years ago.<ref name = AMNH>{{cite web|url=http://www.amnh.org/explore/science-bulletins/earth/documentaries/tsunami-science-reducing-the-risk/ghosts-of-tsunamis-past|title=Ghosts of Tsunamis Past|publisher=American Museum of Natural History|access-date=15 July 2015|archive-url=https://web.archive.org/web/20180828035721/https://www.amnh.org/explore/science-bulletins/earth/documentaries/tsunami-science-reducing-the-risk/ghosts-of-tsunamis-past/|archive-date=28 August 2018|url-status=dead}}</ref> Originally thought to have died slowly due to a gradual rise in sea level,<ref name = "Schulz2015" >{{cite magazine|last=Schulz|first=Kathryn|author-link=Kathryn Schulz|url=http://www.newyorker.com/magazine/2015/07/20/the-really-big-one|title=The Really Big One: An earthquake will destroy a sizable portion of the coastal Northwest. The question is when.|date=July 20, 2015|magazine=[[The New Yorker]]|access-date=July 14, 2015}}</ref> closer inspection yielded a different story: the land plummeted up to two meters during an earthquake.<ref name=AMNH/> Having initially tested [[spruce]] using [[Dendrochronology|tree-ring dating]], they found that the stumps were too rotted to count all the outer rings. However, upon having examined those of the [[Thuja plicata|western red cedar]] and comparing them to the living specimens meters away from the banks, they were able to approximate their year of death. There were rings up until the year 1699, indicating that the incident had occurred shortly thereafter. Root samples confirmed their conclusion, narrowing the time frame to the winter of 1699 to 1700.<ref name = NatGeo>{{cite magazine|url=http://news.nationalgeographic.com/news/2003/12/1208_031208_tsunami.html|archive-url=https://web.archive.org/web/20031211072304/http://news.nationalgeographic.com/news/2003/12/1208_031208_tsunami.html|url-status=dead|archive-date=December 11, 2003|title=Did North American Quake Cause 1700 Japanese Tsunami?|author=Stefan Lovgren|magazine=National Geographic|date=8 December 2003|access-date=15 July 2015}}</ref><ref name = Discover /> As with the arrowgrass site, the banks of the Copalis River are lined with a layer of marsh followed by a layer of sand. Jody Bourgeois and her team went on to demonstrate that the sand cover had originated with a tsunami surge rather than a storm surge.<ref name=AMNH/> In 1995, an international team led by Alan Nelson of the [[USGS]] further corroborated these findings with 85 new samples from the rest of the [[Pacific Northwest]]. All along British Columbia, Washington State, and Oregon, the coast had fallen due to a violent earthquake and been covered by sand from the subsequent tsunami.<ref name=Discover/> A further ghost forest was identified by Gordon Jacoby, a [[Dendrochronology|dendrochronologist]] from Columbia University, {{convert|60|ft|m}} underwater in [[Lake Washington]]. Unlike the other trees, these suffered from a landslide rather than a dip in the fault during a separate event around 900 CE.<ref name = Smithsonian/> ===Activity=== In the 1960s, underground fractures were uncovered by oil companies in [[Puget Sound]]. These were believed to be inactive through the 1990s.<ref name = Smithsonian>{{cite magazine|url=http://www.smithsonianmag.com/science-nature/future-shocks-83897640/?no-ist|title=Future Shocks: Modern science, ancient catastrophes and the endless quest to predict earthquakes|magazine=Smithsonian Magazine|author= Kevin Krajick|date=March 2005|access-date=15 July 2015}}</ref> In the 1980s, geophysicists [[Thomas H. Heaton|Tom Heaton]] and [[Hiroo Kanamori]] of [[California Institute of Technology|Caltech]] compared the generally quiet Cascadia to more active subduction zones elsewhere in the [[Ring of Fire]]. They found similarities to faults in Chile, Alaska, and Japan's [[Nankai Trough]], locations known for [[megathrust earthquake]]s, a conclusion that was met with skepticism from other geophysicists at the time.<ref name = Discover>{{cite magazine|url=http://discovermagazine.com/2012/extreme-earth/01-big-one-earthquake-could-devastate-pacific-northwest|title=The Giant, Underestimated Earthquake Threat to North America|magazine=Discover Magazine|date=13 March 2012|author= Jerry Thompson|access-date=15 July 2015}}</ref> ===Orphan tsunami=== A 1996 study published by seismologist [[Kenji Satake]] supplemented the research by Atwater et al. with tsunami evidence across the Pacific.<ref name=NatGeo/> Japanese annals, which have recorded natural disasters since approximately 600 CE,<ref name = "Schulz2015" /> had reports of a sixteen-foot tsunami that struck the coast of [[Honshu Island]] during the [[Genroku]] era.<ref name=Discover/><ref name=NatGeo/> Since no earthquake had been observed to produce it, scholars dubbed it an "[[orphan tsunami]]".<ref name="Schulz2015" /> Translating the [[Japanese calendar]], Satake found the incident had taken place around midnight of 27–28 January 1700, ten hours after the earthquake occurred. The original magnitude 9.0 earthquake in the Pacific Northwest had thus occurred around 9 pm Pacific Standard Time on 26 January 1700.<ref name="Schulz2015" /> ==Geophysics== [[Image:JuandeFucasubduction.jpg|thumb|upright=1.4|Structure of the Cascadia subduction zone]] The Cascadia subduction zone is a {{convert|1000|km|abbr=on}} long dipping [[Fault (geology)|fault]] that stretches from Northern Vancouver Island to [[Cape Mendocino]] in northern California. It separates the Juan de Fuca and North America plates. New Juan de Fuca plate is created offshore along the [[Juan de Fuca Ridge]].<ref name="Juan de Fuca Volcanics">{{cite web|url=http://vulcan.wr.usgs.gov/Volcanoes/JuanDeFucaRidge/description_juan_de_fuca.html|title=Juan de Fuca Volcanics|access-date=2008-05-06}} USGS</ref><ref name="Roadside Geology of Oregon">{{cite book|title=Roadside Geology of Oregon|year=1978|publisher=Mountain Press|first1=David D.|last1=Alt|first2=Donald W.|last2=Hyndman|location=Missoula, Montana|isbn=978-0-87842-063-6|edition=19th|page=3}}</ref> The Juan de Fuca plate moves toward, and eventually is pushed under the continent (North American plate). The zone separates the [[Juan de Fuca plate]], [[Explorer plate]], [[Gorda plate]], and [[North American plate]]. Here, the [[oceanic crust]] of the Pacific Ocean has been sinking beneath the continent for about 200 million years, and currently does so at a rate of approximately 40 mm/[[year|yr]].<ref name="Juan de Fuca Volcanics"/><ref name="Roadside Geology of Oregon"/> At depths shallower than {{convert|30|km|abbr=on}} or so, the Cascadia zone is locked by friction while stress slowly builds up as the subduction forces act, until the fault's frictional strength is exceeded and the rocks slip past each other along the fault in a [[megathrust earthquake]]. Below {{convert|30|km|abbr=on}} the plate interface exhibits [[episodic tremor and slip]]. The width of the Cascadia subduction zone varies along its length, depending on the angle of the subducted oceanic plate, which heats up as it is pushed deeper beneath the continent. As the edge of the plate sinks and becomes hotter and more molten, the subducting rock eventually loses the ability to store mechanical stress; [[earthquake]]s may result. On the Hyndman and Wang diagram (not shown, click on reference link below) the "locked" zone is storing up energy for an earthquake, and the "transition" zone, although somewhat plastic, could probably rupture.<ref>{{Cite web|url=https://www.researchgate.net/publication/247990703|title=The rupture zone of Cascadia great earthquakes from current deformation and thermal regime|website=ResearchGate}}</ref> The Cascadia subduction zone runs from [[triple junction]]s at its north and south ends. To the north, just below [[Haida Gwaii]], it intersects the [[Queen Charlotte Fault]] and the [[Explorer Ridge]]. To the south, just off Cape Mendocino in California, it intersects the [[San Andreas Fault]] and the [[Mendocino fracture zone]] at the [[Mendocino triple junction]].{{clear}} == Recent seismicity == Subduction zones experience various types of earthquakes (or seismicity); including [[slow earthquake]]s, [[megathrust earthquake]]s, [[interplate earthquake]]s, and [[intraplate earthquake]]s. Unlike other subduction zones on Earth, Cascadia currently experiences low levels of seismicity and has not generated a [[megathrust earthquake]] since January 26, 1700. Despite low levels of seismicity compared to other subduction zones, Cascadia hosts various types of earthquakes that are recorded by seismic and [[Geodesy|geodetic]] instruments, such as [[seismometer]]s and [[GNSS applications|GNSS receivers]]. Tremor, a type of [[Slow earthquake|slow fault slip]], occurs along almost the entire length of Cascadia<ref>{{Cite journal|last1=Brudzinski|first1=Michael R.|last2=Allen|first2=Richard M.|s2cid=6682060|date=2007|title=Segmentation in episodic tremor and slip all along Cascadia|journal=Geology|volume=35|issue=10|pages=907|doi=10.1130/g23740a.1|issn=0091-7613|bibcode=2007Geo....35..907B}}</ref> at regular intervals of 13–16 months.<ref>{{Cite journal|last=Rogers|first=G.|date=2003-06-20|title=Episodic Tremor and Slip on the Cascadia Subduction Zone: The Chatter of Silent Slip|journal=Science|volume=300|issue=5627|pages=1942–1943|doi=10.1126/science.1084783|issn=0036-8075|bibcode=2003Sci...300.1942R|pmid=12738870|s2cid=2672381|doi-access=free}}</ref> Tremor occurs deeper on the subduction interface than the locked area where megathrust earthquakes occur. The depth of tremor along the subduction interface in Cascadia ranges from 28 km to 45 km,<ref name=":0">{{Cite journal|last1=Bostock|first1=Michael G.|last2=Christensen|first2=Nikolas I.|last3=Peacock|first3=Simon M.|date=2019-05-01|title=Seismicity in Cascadia|journal=Lithos|volume=332–333|pages=55–66|doi=10.1016/j.lithos.2019.02.019|issn=0024-4937|bibcode=2019Litho.332...55B|s2cid=134015941}}</ref> and the motion is so slow that it is not felt at the surface by people or animals, but it can be measured [[Geodesy|geodetically]]. The highest density of tremor activity in Cascadia occurs from northern Washington into southern Vancouver Island, and in northern California.<ref name=":0" /> Tremor in Cascadia is monitored by the [[Pacific Northwest Seismic Network]]'s semi-automatic tremor detection system.<ref name=":0" /> The majority of [[interplate earthquake]]s, or earthquakes that occur near the boundaries of tectonic plates, near the Cascadia subduction zone occur in the [[forearc]] of the overriding [[North American plate]] in Washington, west of the [[Cascade Volcanoes|Cascade Volcanic Arc]] and east of where tremor occurs.<ref name=":0" /> These earthquakes are sometimes referred to as crustal earthquakes, and they are capable of causing significant damage due to their relatively shallow depths. A damaging magnitude 7 interplate earthquake occurred on the [[Seattle Fault]] around 900–930 CE<ref>{{Cite journal|last=Atwater|first=Brian|date=1999-03-01|title=Radiocarbon dating of a Seattle earthquake to A.D. 900–930.|journal=Seismological Research Letters|volume=70|issue=2|pages=190–277|doi=10.1785/gssrl.70.2.190|issn=0895-0695}}</ref> that generated 3 meters of uplift and a 4-5 meter tsunami.<ref>{{Cite journal|last=Arcos|first=M. E. M.|date=2012-06-01|title=The A.D. 900-930 Seattle-Fault-Zone Earthquake with a Wider Coseismic Rupture Patch and Postseismic Submergence: Inferences from New Sedimentary Evidence|url=https://pubs.geoscienceworld.org/bssa/article/102/3/1079-1098/326677|journal=Bulletin of the Seismological Society of America|volume=102|issue=3|pages=1079–1098|doi=10.1785/0120110123|issn=0037-1106|bibcode=2012BuSSA.102.1079A|url-access=subscription}}</ref> A substantial number of [[forearc]] [[interplate earthquake]]s also occur in northern California.<ref name=":0" /> Much less interplate seismicity occurs in Oregon compared to Washington and northern California, although Oregon hosts more [[volcanic activity]] than its neighboring states.<ref>{{Cite journal|last1=Sherrod|first1=David R.|last2=Smith|first2=James G.|date=1990|title=Quaternary extrusion rates of the Cascade Range, northwestern United States and southern British Columbia|journal=Journal of Geophysical Research: Solid Earth|volume=95|issue=B12|pages=19465–19474|doi=10.1029/JB095iB12p19465|issn=2156-2202|bibcode=1990JGR....9519465S}}</ref> Intraslab earthquakes, frequently associated with stresses within the subducting plate in [[Convergent boundary|convergent margins]], occur most frequently in northern Cascadia along the west coast of Vancouver Island and in Puget Sound, and in southern Cascadia within the subducting [[Gorda plate]], near the [[Mendocino triple junction]] offshore of northern California. The [[1949 Olympia earthquake]] was a damaging magnitude 6.7 intraslab earthquake that occurred at 52 km depth and caused eight deaths. Another notable intraslab earthquake in the [[Puget Sound]] region was the magnitude 6.8 [[2001 Nisqually earthquake]]. Intraslab earthquakes in Cascadia occur in areas where the subducting plate has high [[curvature]].<ref name=":0" /> Much of the seismicity that occurs off the coast of northern California is due to [[intraplate deformation]] within the [[Gorda plate]]. Similar to the distribution of interplate earthquakes in Cascadia, intraslab earthquakes are infrequent in Oregon, with its strongest earthquake since statehood being the 5.6 magnitude [[1993 Scotts Mills earthquake]], an [[oblique-slip]] quake.<ref name=":0" /><ref>{{Cite web|last=Strauss|first=Mark|title=Oregon Earthquake History|url=https://oregoninsuranceadvisor.com/earthquake-insurance/oregon-earthquake-history/|url-status=live|access-date=2021-06-21|website=Oregon Insurance Advisor|date=20 October 2014|archive-url=https://web.archive.org/web/20150401022212/http://oregoninsuranceadvisor.com:80/earthquake-insurance/oregon-earthquake-history/ |archive-date=2015-04-01 }}</ref> ==Megathrust earthquakes== [[Image:Cascadia earthquake sources.png|thumb|upright=1.4|3D bloc of Cascadia subduction zone with earthquake sources]] ===Earthquake effects=== [[Megathrust earthquake]]s are the most powerful earthquakes known to occur, and can exceed [[Moment magnitude scale|magnitude]] 9.0, which releases 1,000 times more energy than magnitude 7.0 and 1 million times more energy than a magnitude 5.0.<ref name=Nedimovic/><ref>{{Cite web|last=Haas|first=Ryan|date=2015-03-09|title=What Is A 9.0 Earthquake?|url=https://www.opb.org/news/series/unprepared/what-is-a-90-earthquake-/|url-status=live|access-date=2021-06-21|website=Oregon Public Broadcasting|language=en|archive-url=https://web.archive.org/web/20150126173645/http://www.opb.org:80/news/series/unprepared/what-is-a-90-earthquake-/ |archive-date=2015-01-26 }}</ref><ref>{{Cite web|title="How Much Bigger…?" Calculator|url=https://earthquake.usgs.gov/education/calculator.php|url-status=live|access-date=2021-06-21|publisher=United States Geological Survey|department= Earthquake Hazards Program|archive-url=https://web.archive.org/web/20190928152746/https://earthquake.usgs.gov/education/calculator.php |archive-date=2019-09-28 }}</ref> They occur when enough energy (stress) has accumulated in the "locked" zone of the fault to cause a rupture. The magnitude of a megathrust earthquake is proportional to length of the rupture along the fault. The Cascadia subduction zone, which forms the boundary between the Juan de Fuca and North American plates, is a very long sloping fault that stretches from mid-Vancouver Island to Northern California.<ref name="Nedimovic" /> Because of the great length of the fault, the Cascadia subduction zone is capable of producing very large earthquakes if rupture occurs along its entire length. Thermal and deformation studies indicate that the region 60 kilometers (about 40 miles) [[Strike and dip|downdip]] (east) of the deformation front (where plate deformation begins) is fully locked (the plates do not move past each other). Further downdip, there is a transition from fully locked to [[Aseismic creep|aseismic sliding]].<ref name=Nedimovic>{{cite journal | last1 = Nedimović | first1 = Mladen R. | last2 = Hyndman | first2 = Roy D. | last3 = Ramachandran | first3 = Kumar | last4 = Spence | first4 = George D. | title=Reflection signature of seismic and aseismic slip on the northern Cascadia subduction interface | journal=[[Nature (journal)|Nature]] | volume=424 | issue=6947 | date = 24 July 2003 | pages=416–420 | pmid=12879067 | doi=10.1038/nature01840|bibcode = 2003Natur.424..416N | s2cid = 4383885 }}</ref> In 1999, a group of Continuous [[Global Positioning System]] sites registered a brief reversal of motion of approximately 2 centimeters (0.8 inches) over a 50 kilometer by 300 kilometer (about 30 mile by 200 mile) area. The movement was the equivalent of a 6.7 magnitude earthquake.<ref name=Dragert2001>{{cite journal | last1 = Dragert | first1 = Herb | last2 = Wang | first2 = Kelin | last3 = James | first3 = Thomas S. | title=A silent slip event on the deeper Cascadia subduction interface | journal=[[Science (journal)|Science]] | volume=292 | issue=5521 | date = 25 May 2001 | pages=1525–1528 | pmid=11313500 | doi=10.1126/science.1060152|bibcode = 2001Sci...292.1525D | s2cid = 10928887 | doi-access = free }}</ref> The motion did not trigger an earthquake and was only detectable as silent, non-earthquake seismic signatures.<ref name=rogers2003>{{cite journal | last1 = Rogers | first1 = Garry | last2 = Dragert | first2 = Herb | title=Episodic tremor and slip on the Cascadia subduction zone: the chatter of silent slip | journal=[[Science (journal)|Science]] | volume=300 | issue=5627 | date = 20 June 2003 | pages = 1942–1943 | pmid=12738870 | doi=10.1126/science.1084783|bibcode = 2003Sci...300.1942R | s2cid = 2672381 | doi-access = free }}</ref> In 2004, a study conducted by the Geological Society of America analyzed the potential for land subsidence along the Cascadia subduction zone. It postulated that several towns and cities on the west coast of Vancouver Island, such as [[Tofino]] and [[Ucluelet]], are at risk for a sudden, earthquake initiated, 1–2 m subsidence.<ref>{{cite journal |title=Coseismic subsidence in the 1700 great Cascadia earthquake: Coastal estimates versus elastic dislocation models| first1 = Lucinda J. | last1 = Leonard | first2 = Roy D. | last2 = Hyndman | first3 = Stéphane | last3 = Mazzotti | s2cid = 62833386 | doi = 10.1130/B25369.1 | journal = [[GSA Bulletin]] | volume = 116 | issue = 5–6 | pages = 655–670 | bibcode = 2004GSAB..116..655L |year=2004}}</ref> ===San Andreas Fault connection=== Studies of past earthquake traces on both the northern [[San Andreas Fault]] and the southern Cascadia subduction zone indicate a correlation in time which may be evidence that quakes on the Cascadia subduction zone may have triggered most of the major quakes on the northern San Andreas during at least the past 3,000 years or so. The evidence also shows the rupture direction going from north to south in each of these time-correlated events. The [[1906 San Francisco earthquake]] seems to have been a major exception to this correlation, however, as it was not preceded by a major Cascadia quake.<ref>{{Cite web|url=https://www.sciencedaily.com/releases/2008/04/080403131923.htm|title=Earthquakes Along The Cascadia And San Andreas Faults May Be Linked, Affecting Risk To San Francisco Bay Region|website=ScienceDaily}}</ref> === Earthquake timing === {| class="wikitable sortable" align="right" style="text-align:center;" |+ Great earthquakes ! colspan="2" | estimated year !! interval |- ! 2005 source<ref name="Atwater-et-al-2005"> {{cite book | author=Brian F Atwater | author2=Musumi-Rokkaku Satoko | author3=Satake Kenji | author4=Tsuji Yoshinobu | author5=Ueda Kazue | author6=David K Yamaguchi | year=2005 | title=The Orphan Tsunami of 1700 – Japanese Clues to a Parent Earthquake in North America | edition=U.S. Geological Survey Professional Paper 1707 | publisher=University of Washington Press | location=Seattle and London | isbn=978-0-295-98535-0 | url=https://archive.org/details/orphantsunamiof100atwa/page/100 | page=[https://archive.org/details/orphantsunamiof100atwa/page/100 100 (timeline diagram)] | url-access=registration }} </ref> !! 2003 source<ref name="Atwater-et-al-2003"> {{citation |author=Brian F Atwater |author2=Martitia P Tuttle |author3=Eugene S Schweig |author4=Charles M Rubin |author5=David K Yamaguchi |author6=Eileen Hemphill-Haley |title=Earthquake Recurrence Inferred from Paleoseismology |journal=Developments in Quaternary Science |publisher=Elsevier BV |issn=1571-0866 |year=2003 |volume=1 |doi=10.1016/S1571-0866(03)01015-7 |url=http://www.gps.caltech.edu/~simons/TectonicObservatory/AtwaterQuantSciece1.pdf |access-date=2011-03-15 |at=Figures 10 and 11 (pp 341, 342); article pp 331–350 |url-status=dead |archive-url=https://web.archive.org/web/20120319210743/http://www.gps.caltech.edu/~simons/TectonicObservatory/AtwaterQuantSciece1.pdf |archive-date=2012-03-19 |series=Developments in Quaternary Sciences |isbn=9780444514707 }} </ref> !! (years) <!-- See this article's talk page for more about this table. --> |- | colspan="2" | <span style="display:none">Y</span> About 9 p.m., January 26, 1700 ([[Old Style and New Style dates|NS]]) || 780 |- | <span style="display:none">W</span> 780–1190 [[Common Era|CE]] || 880–960 CE || 210 |- | <span style="display:none">U</span> 690–730 CE || 550–750 CE || 330 |- | <span style="display:none">S</span> 350–420 CE || 250–320 CE || 910 |- | <span style="display:none">N</span> 660-440 [[Common Era|BCE]] || 610–450 BCE || 400 |- | <span style="display:none">L</span> 980–890 BCE || 910–780 BCE || 250 |- | <span style="display:none">J</span> 1440–1340 BCE || 1150–1220 BCE || unknown |} The last known great earthquake in the northwest was the [[1700 Cascadia earthquake]], {{age in years|26 JAN 1700}} years ago. [[Geology|Geological]] evidence indicates that great earthquakes (> magnitude 8.0) may have occurred sporadically at least seven times in the last 3,500 years, suggesting a return time of about 500 years.<ref name=Discover/><ref name = NatGeo/><ref name = AMNH/> Seafloor core evidence indicates that there have been forty-one subduction zone earthquakes on the Cascadia subduction zone in the past 10,000 years, suggesting a general average earthquake recurrence interval of only 243 years.<ref name="Schulz2015" /> Of these 41, nineteen have produced a "full margin rupture", wherein the entire fault opens up.<ref name="Discover"/> By comparison, similar [[subduction]] zones in the world usually have such earthquakes every 100 to 200 years; the longer interval here may indicate unusually large stress buildup and subsequent unusually large earthquake slip.<ref name=PNSN>{{cite web|url=http://pnsn.org/outreach/earthquakesources/csz|title=Cascadia Subduction Zone|publisher=Pacific Northwest Seismic Network}}</ref> There is also evidence of accompanying [[tsunami]]s with every earthquake. One strong line of evidence for these earthquakes is convergent timings for fossil damage from tsunamis in the [[Pacific Northwest]] and historical Japanese records of tsunamis.<ref name=japan>{{cite web|url=http://pubs.usgs.gov/pp/pp1707/pp1707.pdf|title=The Orphan Tsunami of 1700—Japanese Clues to a Parent Earthquake in North America|access-date=2008-05-06}} USGS Professional Paper 1707</ref> The next rupture of the Cascadia subduction zone is anticipated to be capable of causing widespread destruction throughout the [[Pacific Northwest]].<ref name=CREW>{{cite web|url=http://www.crew.org/sites/default/files/CREWCascadiaFinal.pdf|title=Cascade Range Earthquake Workgroup – Magnitude 9 scenario|access-date=2012-03-27|archive-url=https://web.archive.org/web/20121024010654/http://crew.org/sites/default/files/CREWCascadiaFinal.pdf|archive-date=2012-10-24|url-status=dead}}</ref> === Forecasts of the next major earthquake === {{See also|1700 Cascadia earthquake#Future threats}} Prior to the 1980s, scientists thought that the subduction zone did not generate earthquakes like other subduction zones around the world, but research by [[Brian Atwater]] and [[Kenji Satake]] tied together evidence of a large tsunami on the Washington coast with documentation of an orphan tsunami in Japan (a tsunami without an associated earthquake). The two pieces of the puzzle were linked, and they then realized that the subduction zone was more hazardous than previously suggested. In 2009, some geologists predicted a 10% to 14% probability that the Cascadia subduction zone will produce an event of magnitude 9.0 or higher in the next 50 years.<ref name="Sooner">{{cite news | url = http://www.oregonlive.com/news/index.ssf/2009/04/big_earthquake_coming_sooner_t.html | newspaper = [[The Oregonian]] | title=Big earthquake coming sooner than we thought, Oregon geologist says | date=April 19, 2009 | first = Lori | last = Tobias }}</ref> In 2010, studies suggested that the risk could be as high as 37% for earthquakes of magnitude 8.0 or higher.<ref>{{cite news | url = http://www.nature.com/news/2010/100531/full/news.2010.270.html | title = Risk of giant quake off American west coast goes up | first = Richard A. | last = Lovett | access-date = 2010-06-08 | doi = 10.1038/news.2010.270 | journal = [[Nature (journal)|Nature]] | date = 31 May 2010}}</ref><ref>{{cite press release | url = https://www.sciencedaily.com/releases/2010/05/100524121250.htm | title = Odds are about 1-in-3 that mega-earthquake will hit Pacific Northwest in next 50 years, scientists say | date = May 25, 2010 | publisher = [[Oregon State University]] | via = [[Science Daily]] }}</ref> Geologists and civil engineers have broadly determined that the Pacific Northwest region is not well prepared for such a colossal earthquake. The earthquake is expected to be similar to the [[2011 Tōhoku earthquake and tsunami]], because the rupture is expected to be as long as the [[2004 Indian Ocean earthquake and tsunami]]. The resulting [[tsunami]] might reach heights of approximately 30 meters (100 ft).<ref name="Sooner"/> [[FEMA]] estimates some 13,000 fatalities from such an event, with another 27,000 injured, which would make it the deadliest natural disaster in American, and North American, history.<ref name="Schulz2015" /><ref>{{Cite web|last=Roos|first=Dave|date=2020-09-18|title=The Deadliest Natural Disasters in U.S. History|url=https://www.history.com/news/deadliest-natural-disasters-us-storm-flood-hurricane-fire|url-status=live|access-date=2021-06-21|website=HISTORY|archive-url=https://web.archive.org/web/20181203045559/https://www.history.com/news/deadliest-natural-disasters-us-storm-flood-hurricane-fire |archive-date=2018-12-03 }}</ref><ref>{{Cite web|last=Powell|first=Kimberly|date=2018-07-19|title=10 Deadliest Natural Disasters in U.S. History|url=https://www.thoughtco.com/top-deadliest-us-natural-disasters-1422019|url-status=live|access-date=2021-06-21|website=ThoughtCo.|archive-url=https://web.archive.org/web/20171014183218/https://www.thoughtco.com/top-deadliest-us-natural-disasters-1422019 |archive-date=2017-10-14 }}</ref> FEMA further predicts that a million people will be displaced, with yet another 2.5 million requiring food and water. An estimated 1/3 of public safety workers will not respond to the disaster due to a collapse in infrastructure and a desire to ensure the safety of themselves and their loved ones.<ref name="Schulz2015" /> Other analyses predict that even a magnitude 6.7 earthquake in Seattle would result in 7,700 dead and injured, $33 billion in damage, 39,000 buildings severely damaged or destroyed, and 130 simultaneous fires.<ref name = Smithsonian/> ==Cascade Volcanic Arc== [[File:Cascade Volcanic Arc.jpg|thumb|upright=1.4|Juan de Fuca triple junctions and the Cascade Volcanic Arc]] {{Main|Cascade Volcanoes}} The [[Cascade Volcanic Arc]] is a [[continental arc]] of [[volcanoes]] that extends from northern [[California]] to the coastal peninsula of [[Alaska]].<ref>{{cite web |url=https://geology.com/plate-tectonics.shtml |title= Plate Tectonics Map – Plate Boundary Map |access-date=2020-11-18 |first1=Hobart M |last1=King| website=geology.com}}</ref> The arc consists of a series of [[Quaternary]] age stratovolcanoes that grew on top of pre-existing geologic materials that ranged from [[Miocene]] volcanics to [[Glacier|glacial ice]].<ref name="emporia.edu"/> The Cascade Volcanic arc is located approximately 100 km inland from the coast, and forms a north-to-south chain of peaks that average over 3,000 m (10,000 ft) in elevation.<ref name="emporia.edu"/> The major peaks from south to north include: * [[Lassen Peak]] and [[Mount Shasta]] (California) * [[Crater Lake]] (Mazama), [[Three Sisters (Oregon)|Three Sisters]], [[Mount Jefferson (Oregon)|Mount Jefferson]], [[Mount Hood]] (Oregon) * [[Mount Adams (Washington)|Mount Adams]], [[Mount St. Helens]], [[Mount Rainier]], [[Glacier Peak]], [[Mount Baker]] (Washington) * [[Mount Garibaldi]] and [[Mount Meager massif]] (British Columbia) The most active volcanoes in the chain include Mount St. Helens, Mount Baker, Lassen Peak, Mount Shasta, and Mount Hood. Mount St. Helens captured worldwide attention when it [[1980 eruption of Mount St. Helens|erupted catastrophically in 1980]].<ref name="emporia.edu"/> St. Helens continues to rumble, albeit more quietly, emitting occasional steam plumes and experiencing small earthquakes, both signs of continuing magmatic activity.<ref name="emporia.edu"/> Most of the volcanoes have a main, central vent from which the most recent eruptions have occurred. The peaks are composed of layers of solidified [[Andesite|andesitic]] to [[Dacite|dacitic]] [[magma]], and the more siliceous (and explosive) [[rhyolite]]. ===Volcanoes above the subduction zone=== The volcanoes above the subduction zone include: {{Div col|colwidth=15em}} * [[Silverthrone Caldera]] * [[Mount Meager massif]] * [[Mount Cayley]] * [[Mount Garibaldi]] * [[Mount Baker]] * [[Glacier Peak]] * [[Mount Rainier]] * [[Mount St. Helens]] * [[Mount Adams (Washington)|Mount Adams]] * [[Mount Hood]] * [[Mount Jefferson (Oregon)|Mount Jefferson]] * [[Three Sisters (Oregon)|Three Sisters]] * [[Newberry Volcano]] * [[Mount Mazama]] (Crater Lake) * [[Mount McLoughlin]] * [[Medicine Lake Volcano]] * [[Mount Shasta]] * [[Lassen Peak]] * [[Black Butte (Oregon)|Black Butte]] * [[Black Butte (Siskiyou County, California)|Black Butte (California)]] {{Div col end}} == See also == * [[Astoria Fan]] * [[Cascade Range]] * [[Cascadia (region)]] * [[Cascadia Channel]] * [[Cascadia Region Earthquake Science Center|Cascadia Region Earthquake Science Center (CRESCENT)]] * [[Geology of the Pacific Northwest]] * [[Neskowin Ghost Forest]] * [[North Cascades National Park]] * [[Plate tectonics]] {{Clear}} ==References== {{Reflist}} ==Further reading== *Owen, R., 2024, A clearer picture of Cascadia emerges from modern mapping, Temblor, {{doi|10.32858/temblor.347}} ==External links== * {{cite web |title=Turbidite event history—Methods and implications for Holocene paleoseismicity of the Cascadia subduction zone |url=http://pubs.usgs.gov/pp/pp1661f |publisher=United States Geological Survey |id=Professional Paper 1661–F |editor=Robert Kayen |author=Chris Goldfinger |author2=C. Hans Nelson |author3=Ann E. Morey |author4=Joel E. Johnson |author5=Jason R. Patton |author6=Eugene Karabanov |author7=Julia Gutiérrez-Pastor |author8=Andrew T. Eriksson |author9=Eulàlia Gràcia |author10=Gita Dunhill |author11=Randolph J. Enkin |author12=Audrey Dallimore |author13=Tracy Vallier |year=2012 |ref=none}} * {{cite journal | author=Atwater, BF | title=Evidence for great Holocene earthquakes along the outer coast of Washington State| journal=[[Science (journal)|Science]] | volume=236 | issue=4804 | year=1987 | pages=942–44 | doi=10.1126/science.236.4804.942 | pmid=17812748|bibcode = 1987Sci...236..942A | citeseerx=10.1.1.175.8056| s2cid=39790838 |ref=none}} * [https://web.archive.org/web/20160401065513/http://www.dailywireless.org/2009/04/21/cascadia-peril-09/ "Cascadia Peril '09"] at dailywireless.org * [https://earthquake.usgs.gov/earthquakes/shakemap/global/shake/Casc9.0_se/ 9.0 Shakemap Scenario] * [https://www.youtube.com/watch?v=-EGqKhWc5wU The Really Big One] – University of California Television * [https://www.youtube.com/watch?v=UJ7Qc3bsxjI Great Earthquakes of the Pacific Northwest] – [[Central Washington University]] * [https://www.youtube.com/watch?v=Iy5a2P3zXl4 Toast, tsunamis and the really big one | Chris Goldfinger | TEDxMtHood] – TEDx {{Faults}} {{Authority control}} [[Category:Cascade Volcanoes]] [[Category:Geologic provinces of California]] [[Category:Geology of British Columbia]] [[Category:Geology of Oregon]] [[Category:Geology of Washington (state)]] [[Category:Natural hazards in British Columbia]] [[Category:Seismic zones of British Columbia]] [[Category:Subduction zones]]
Edit summary
(Briefly describe your changes)
By publishing changes, you agree to the
Terms of Use
, and you irrevocably agree to release your contribution under the
CC BY-SA 4.0 License
and the
GFDL
. You agree that a hyperlink or URL is sufficient attribution under the Creative Commons license.
Cancel
Editing help
(opens in new window)
Pages transcluded onto the current version of this page
(
help
)
:
Template:Age in years
(
edit
)
Template:Authority control
(
edit
)
Template:Citation
(
edit
)
Template:Cite book
(
edit
)
Template:Cite journal
(
edit
)
Template:Cite magazine
(
edit
)
Template:Cite news
(
edit
)
Template:Cite press release
(
edit
)
Template:Cite web
(
edit
)
Template:Clear
(
edit
)
Template:Convert
(
edit
)
Template:Coord
(
edit
)
Template:Cvt
(
edit
)
Template:Div col
(
edit
)
Template:Div col end
(
edit
)
Template:Doi
(
edit
)
Template:Faults
(
edit
)
Template:Main
(
edit
)
Template:Multiple image
(
edit
)
Template:Reflist
(
edit
)
Template:See also
(
edit
)
Template:Short description
(
edit
)