The Queen Charlotte Fault is an active transform fault that marks the boundary of the North American plate and the Pacific plate. [1] [2] It is Canada's right-lateral strike-slip equivalent to the San Andreas Fault to the south in California. [3] The Queen Charlotte Fault forms a triple junction south with the Cascadia subduction zone and the Explorer Ridge (the Queen Charlotte Triple Junction). The Queen Charlotte Fault (QCF) forms a transpressional plate boundary, and is as active as other major transform fault systems (i.e. San Andreas, Alpine) in terms of slip rates and seismogenic potential. [4] It sustains the highest known deformation rates among continental or continent-ocean transform systems globally, accommodating greater than 50mm/yr dextral offset. [5] The entire approximately 900 km offshore length has ruptured in seven greater than magnitude 7 events during the last century, making the cumulative historical seismic moment release higher than any other modern transform plate boundary system. [6]
The fault is named for the Queen Charlotte Islands (now Haida Gwaii) which lie just north of the triple junction. The Queen Charlotte Fault continues northward along the Alaskan coast where it is called the Fairweather Fault. [7] The two segments are collectively called the Queen Charlotte-Fairweather Fault System.
The junction of the Queen Charlotte, Fairweather, and Transition faults is located at the southeastern tip of the Yakutat block, an oceanic plateau and microplate. [8] The southern boundary of the QCF is marked by the complex Pacific–North American–Explorer triple junction off the coast of southern British Columbia. [8] The Queen Charlotte Fault continues northward along the Alaskan coast where it is called the Fairweather Fault. The two segments are collectively called the Queen Charlotte-Fairweather Fault System. The current state of transpressive plate boundary systems results from spatial and temporal changes between both rheologic and kinematic parameters. From north to south, there is a decreasing rate of convergence [8] and change in fault obliquity which appears to divide the fault into at least three distinct kinematic zones [2] along strike with associated changes in seafloor morphology, fault structure, and seismicity. [3] We have the northern, central and southern segments with maximum obliquity (approximately 15°-20°) occurring south of 53.2°N and minimum obliquity (less than 5°) occurring north of 56°N. Existing geophysical data suggest abrupt transitions in deformation mechanisms and plate boundary dynamics across these boundaries with incipient underthrusting and strain partitioning in the south along Haida Gwaii, [9] distributed transpression in the central segment, [8] and highly localized strike-slip deformation in the north. [5] There are various mechanisms proposed to accommodate oblique convergence along the QCF, this include underthrusting and strain partitioning, [2] crustal thickening, [10] and distributed shear. [3] [8] Through geologic time, a change in pacific plate motion beginning as recently as approximately 6 Ma [11] or as early as approximately 12 Ma [12] caused an increase in convergence along the entire length of the fault and initiated underthrusting [13] along the southern segment where convergence is highest, [2] a process that ultimately led to the 2012 Haida Gwaii thrust earthquake. [14]
Crustal deformation via strain partitioning likely dominates the southern segment, [15] [16] [8] as evidenced by the thrust mechanism of the 2012 Haida Gwaii earthquake, [17] where geoscientists observed downwarping and normal faulting on the Pacific Plate west of Haida Gwaii. [18] This hypothesis is also supported by the morphology of the Queen Charlotte Terrace, an approximately 30 km-wide deformed accretionary prism-like complex west of the main QCF trace. [19] Several recent studies based on seismicity, GPS observations of coseismic and postseismic deformation, and thermal modeling support the presence of a shallow plate boundary thrust. [20] [21] [22] [23]
In the central segment, abrupt changes in both seafloor morphology and structural geometry accompany a decrease in convergence angle. The Queen Charlotte Terrace widens and deepens, forming a series of oblique ridges and basins west of the QCF main trace. [24] [8] There is a distinct structural transition due to a change in the stress regime from pure shear in the southern QCF segment to simple shear in the central QCF segment as a result of convergence decreasing below a critical angle of approximately 15°. [8]
In the northern segment, which bore the epicenter of the strike-slip 2013 Craig earthquake, bathymetric data suggests that the ridge-basin complex gives way to simpler fault morphology. [5] Deformation largely occurs on what appears to be a single strike-slip structure. [5] The same location also marks earthquake rupture boundaries between the 2013 Craig event [25] and the 1972 M7.6 Sitka event, [26] [27] as well as the inferred intersection of the Chatham Strait Fault and the Aja Fracture Zone (FZ) with the Queen Charlotte Fault; the Aja FZ also marks an approximately 3 million year contrast in Pacific Plate crustal age. [2] Accommodation of strike-slip plate motion along a narrow deformation zone is consistent with focal mechanisms determined for the Craig event and its aftershocks. [28] Combined with other observations along the fault, this behavior implies that there may be a critical angle of obliquity within the simple shear regime at which distributed shear across multiple structures is not sustainable, and deformation can be more easily accommodated on a single structure.The fault has been the source of large, very large, and great earthquakes.
Date | M | Damage | Article |
---|---|---|---|
1929 | ~7 | ||
1949 | 8.1 | Landslides, housing and infrastructure damage, oil tank collapse | 1949 Queen Charlotte Islands earthquake |
1958 | 7.8 | Landslide, megatsunami (524 m), housing and infrastructure destruction, 5 casualties | 1958 Lituya Bay earthquake and megatsunami |
1970 | 7.4 | Landslides | |
1990 | 5.3 | Minor | |
2001 | 6.3 | Minor | |
2004 | 6.8 | Land slippage | |
2008 | 6.5 | Minor | |
2009 | 6.6 | Minor | |
2012 | 7.8 | Temporary desiccation of hot springs, 1 casualty (indirect) | 2012 Haida Gwaii earthquake |
2013 | 7.6 | Minor | 2013 Craig, Alaska earthquake |
2014 | 6.0 | Undersea fiber-optic cable damage, causing widespread telecommunications outages | 2014 Palma Bay earthquake |
Six large earthquakes have occurred along the Queen Charlotte Fault within the last hundred years: a magnitude 7 event in 1929, a magnitude 8.1 in 1949 (Canada's largest recorded earthquake since the 1700 Cascadia earthquake), a magnitude 7.8 in 1958, a magnitude 7.4 in 1970, a magnitude 7.8 in 2012, and a magnitude 7.6 in 2013. [4]
The P nodal focal mechanism for the 1949 earthquake indicates a virtually pure strike-slip movement with a northwest-striking nodal plane corresponding to the strike of the fault. [4] This is similar to the 1970 earthquake, which also showed a strike-slip movement with a small but significant thrust component, consistent with relative plate motion. The 1949 earthquake was larger than the 1906 San Francisco earthquake, causing nearly a 500 kilometer-long segment of the Queen Charlotte Fault to break.
The 1958 earthquake had a magnitude of 7.8 and led to a major landslide in Lituya Bay, Alaska. This resulted in a 1,720-foot (524-meter) tsunami that crashed into a mountainside, the largest ever recorded tsunami run-up. [29]
The 2012 magnitude 7.8 earthquake struck off the western coast of Haida Gwaii at around 8:10pm Pacific Time on Saturday 27 October. This was the biggest quake in Canadian territory since 1949. Aftershocks as large as 6.3 magnitude were reported. A 45-cm tsunami was reported locally. Alerts were sent across the Pacific Basin. [30] This earthquake did not have any major impacts, except for the temporary desiccation of the hotsprings on Hotspring Island. The springs seemed to have returned to borderline normal functioning as of July 2014. [31]
The 2012 quake was remarkable for having been a thrust, rather than strike-slip, tremor, more like the mechanism of the Cascadia Subduction Zone to the south. [32] Recent detailed seafloor mapping has revealed the expression of the Queen Charlotte Fault on the seafloor, [33] including the truncation of submarine canyons that occur along the continental slope. [34]
The Cascadia subduction zone is a 960 km fault at a convergent plate boundary, about 112-160 km off the Pacific Shore, that stretches from northern Vancouver Island in Canada to Northern California in the United States. It is capable of producing 9.0+ magnitude earthquakes and tsunamis that could reach 30m. 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. It is a very long, sloping subduction zone where the Explorer, Juan de Fuca, and 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, and terminating at about Vancouver Island in British Columbia.
Megathrust earthquakes occur at convergent plate boundaries, where one tectonic plate is forced underneath another. The earthquakes are caused by slip along the thrust fault that forms the contact between the two plates. These interplate earthquakes are the planet's most powerful, with moment magnitudes (Mw) that can exceed 9.0. Since 1900, all earthquakes of magnitude 9.0 or greater have been megathrust earthquakes.
The 1999 Hector Mine earthquake occurred in Southern California, United States, on October 16 at 02:46:50 PDT. Its moment magnitude was 7.1 and the earthquake was preceded by 12 foreshocks, the largest of which had a magnitude of 3.8. The event is thought to have been triggered by the 1992 Landers earthquake which occurred seven years earlier. It also deformed nearby faults vertically and horizontally. The earthquake's hypocenter was at a depth of 20 kilometers and its epicenter at 34.603° N 116.265° W.
The Newport–Inglewood Fault is a right-lateral strike-slip fault in Southern California. The fault extends for 47 mi (76 km) from Culver City southeast through Inglewood and other coastal communities to Newport Beach at which point the fault extends east-southeast into the Pacific Ocean where it is known as the Rose Canyon Fault. The fault can be inferred on the Earth's surface as passing along and through a line of hills extending from Signal Hill to Culver City. The fault has a slip rate of approximately 0.6 mm (0.024 in)/year and is predicted to be capable of a 6.0–7.4 magnitude earthquake on the moment magnitude scale. A 2017 study concluded that, together, the Newport–Inglewood Fault and Rose Canyon Fault could produce an earthquake of 7.3 or 7.4 magnitude.
The 1949 Queen Charlotte Islands earthquake struck Haida Gwaii and the Pacific Northwest coast at 8:01 p.m. PDT on August 21. The earthquake had a moment magnitude of 8.0 and a surface wave magnitude of 8.1. The maximum Mercalli Intensity in the event was VIII (Severe).
In seismology, a supershear earthquake is an earthquake in which the propagation of the rupture along the fault surface occurs at speeds in excess of the seismic shear wave (S-wave) velocity. This causes an effect analogous to a sonic boom.
The 2002 Denali earthquake occurred at 22:12:41 UTC November 3 with an epicenter 66 km ESE of Denali National Park, Alaska, United States. This 7.9 Mw earthquake was the largest recorded in the United States in 37 years. The shock was the strongest ever recorded in the interior of Alaska. Due to the remote location, there were no fatalities and only one injury.
The 1833 Sumatra earthquake occurred on November 25 at about 22:00 local time, with an estimated magnitude in the range of 8.8–9.2 Mw . It caused a large tsunami that flooded the southwestern coast of the island. There are no reliable records of the loss of life, with the casualties being described only as 'numerous'. The magnitude of this event has been estimated using records of uplift taken from coral microatolls.
The 1797 Sumatra earthquake occurred at 22:00 local time on February 10. It was the first in a series of great earthquakes that ruptured part of the Sumatran segment of the Sunda megathrust. It caused a damaging tsunami that was particularly severe near Padang, where a 150–200 ton English ship was driven 1 km inland up the Arau River.
The 1861 Sumatra earthquake occurred on 16 February and was the last in a sequences of earthquakes that ruptured adjacent parts of the Sumatran segment of the Sunda megathrust. It caused a devastating tsunami which led to several thousand fatalities. The earthquake was felt as far away as the Malay peninsula and the eastern part of Java. The rupture area for the 2005 Nias–Simeulue earthquake is similar to that estimated for the 1861 event.
The 1935 Sumatra earthquake occurred at 09:35 local time on 28 December. It had a magnitude of Mw 7.7 and a maximum felt intensity of VII (Damaging) on the European macroseismic scale. It triggered a minor tsunami.
The 1943 Alahan Panjang earthquakes occurred on June 8 and June 9 UTC in Sumatra, then under Japanese occupation. This was an earthquake doublet.
The 1762 Arakan earthquake occurred at about 17:00 local time on 2 April, with an epicentre somewhere along the coast from Chittagong to Arakan in modern Myanmar. It had an estimated moment magnitude between 8.5 and 8.8 and a maximum estimated intensity of XI (Extreme). It triggered a local tsunami in the Bay of Bengal and caused at least 200 deaths. The earthquake was associated with major areas of both uplift and subsidence. It is also associated with a change in course of the Brahmaputra River to from east of Dhaka to 150 kilometres (93 mi) to the west via the Jamuna River.
The 2012 Haida Gwaii earthquake occurred just after 8:04 p.m. PDT on October 27. The shock had a moment magnitude of 7.8 and a maximum Mercalli Intensity of V (Moderate). The earthquake's epicentre was on Moresby Island of the Haida Gwaii archipelago. This was the second largest Canadian earthquake ever recorded by a seismometer, after the 1949 Queen Charlotte Islands earthquake, about 135 kilometres (84 mi) away. One person died due to a car crash related to the tsunami in Oahu, Hawaii.
The Main Himalayan Thrust (MHT) is a décollement under the Himalaya Range. This thrust fault follows a NW-SE strike, reminiscent of an arc, and gently dips about 10 degrees towards the north, beneath the region. It is the largest active continental megathrust fault in the world.
The 2013 Craig, Alaska earthquake struck on January 5, at 12:58 am (UTC–7) near the city of Craig and Hydaburg, on Prince of Wales Island. The Mw 7.5 earthquake came nearly three months after an Mw 7.8 quake struck Haida Gwaii on October 28, in 2012. The quake prompted a regional tsunami warning to British Columbia and Alaska, but it was later cancelled. Due to the remote location of the quake, there were no reports of casualties or damage.
The 1906 Manasi earthquake (玛纳斯地震), also known as the Manas earthquake occurred in the morning of December 23, 1906, at 02:21 UTC+8:00 local time or December 22, 18:21 UTC. It measured 8.0–8.3 on the moment magnitude scale and 8.3 on the surface-wave magnitude scale. The epicenter of this earthquake is located in Manas County, Xinjiang, China. An estimated 280–300 people died and another 1,000 more were injured by the earthquake.
The 1980 Nepal earthquake devastated the Nepal–India border region on the evening of July 29. The epicenter of the 6.6 Mw earthquake was located in Nepal, northwest of Khaptad National Park. At least 200 people died and 5,600 were injured in the disaster. Extensive damage occurred on both sides of the border, amounting to 245 million USD.
The 1933 Sumatra earthquake or Liwa earthquake occurred in West Lampung Regency, Lampung Province, Indonesia on June 25. The earthquake had an estimated surface-wave magnitude (Ms ) of 7.7 occurring at a shallow depth of 20 km. It had an epicenter onshore, devastating the city of Liwa. At least 76 people were reported killed, although the death toll may have been in the thousands. Aftershocks followed, including one which was strong enough to cause additional fatalities. The mainshock also triggered a nearby volcanic eruption two weeks later, killing some people.
The 1979 Saint Elias earthquake occurred near noon local time on the 28th of February. It measured Mw 7.4–7.6. Though the maximum recorded Modified Mercalli intensity was VII, damage was minimal and there were no casualties due to the remoteness of the faulting. The epicenter lies near the Alaskan border between America and Canada.