The Queen Charlotte Fault is an active

transform fault A transform fault or transform boundary, is a fault (geology), fault along a plate boundary where the motion (physics), motion is predominantly Horizontal plane, horizontal. It ends abruptly where it connects to another plate boundary, either an ...

on the boundary between the

North American North America is a continent in the Northern and Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Caribbean Sea, and to the sou ...

plate and Pacific plates. It is

Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...

's right-lateral strike-slip equivalent to the

San Andreas Fault The San Andreas Fault is a continental Fault (geology)#Strike-slip faults, right-lateral strike-slip transform fault that extends roughly through the U.S. state of California. It forms part of the tectonics, tectonic boundary between the Paci ...

to the south in

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

. The Queen Charlotte Fault forms a

triple junction A triple junction is the point where the boundaries of three tectonic plates meet. At the triple junction each of the three boundaries will be one of three types – a ridge (R), trench (T) or transform fault (F) – and triple junctions can be ...

at its southern with the

Cascadia subduction zone The Cascadia subduction zone is a convergent plate boundary, about 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+ m ...

and the

Explorer Ridge The Explorer Ridge is a mid-ocean ridge, a divergent tectonic plate boundary located about west of Vancouver Island, British Columbia, Canada. It lies at the northern extremity of the Pacific spreading axis. To its east is the Explorer plate ...

(the

Queen Charlotte triple junction The Queen Charlotte triple junction is a geologic triple junction where three tectonic plates meet: the Pacific plate, the North American plate, and the Explorer plate. The three plate boundaries which intersect here are the Queen Charlotte Fau ...

). The Queen Charlotte Fault (QCF) forms a

transpression In geology, transpression is a type of Strike-slip fault, strike-slip deformation that deviates from simple shear because of a simultaneous component of shortening perpendicular to the fault plane. This movement ends up resulting in oblique shear. ...

al plate boundary, and is as active as other major transform fault systems (such as San Andreas or

Alpine Alpine may refer to any mountainous region. It may also refer to: Places Europe * Alps, a European mountain range ** Alpine states, which overlap with the European range Australia * Alpine, New South Wales, a Northern Village * Alpine National P ...

) in terms of slip rates and seismogenic potential. It sustains the highest-known deformation rates among

continental Continental may refer to: Places * Continental, Arizona, a small community in Pima County, Arizona, US * Continental, Ohio, a small town in Putnam County, US Arts and entertainment * ''Continental'' (album), an album by Saint Etienne * Continen ...

or continent-ocean transform systems globally, accommodating more than 50 mm/yr of

dextral Sinistral and dextral, in some scientific fields, are the two types of chirality ("handedness") or relative direction. The terms are derived from the Latin words for "left" (''sinister'') and "right" (''dexter''). Other disciplines use different ...

offset. The entire offshore length has ruptured in seven magnitude 7+ events during the last century, making the cumulative historical

seismic moment Seismic moment is a quantity used by seismologists to measure the size of an earthquake. The scalar seismic moment M_0 is defined by the equation M_0=\mu AD, where *\mu is the shear modulus of the rocks involved in the earthquake (in pascal (unit) ...

release higher than any other modern transform plate boundary system. The fault is named for the Queen Charlotte Islands (now

Haida Gwaii Haida Gwaii (; / , literally "Islands of the Haida people"), previously known as the Queen Charlotte Islands, is an archipelago located between off the British Columbia Coast, northern Pacific coast in the Canadian province of British Columbia ...

), which lie just north of the triple junction. The Queen Charlotte Fault continues northward along the

Alaska Alaska ( ) is a non-contiguous U.S. state on the northwest extremity of North America. Part of the Western United States region, it is one of the two non-contiguous U.S. states, alongside Hawaii. Alaska is also considered to be the north ...

n coast, where it is called the Fairweather Fault. The two segments are collectively called the Queen Charlotte-Fairweather Fault System.

Fault orientation and plate motion

The junction of the Queen Charlotte, Fairweather, and Transition faults is located at the southeastern tip of the

Yakutat block The Yakutat Block is a terrane in the process of accreting to the North American continent along the south central coast of Alaska. It has been displaced about northward since the Cenozoic along the Queen Charlotte-Fairweather fault system. The ...

, an oceanic plateau and microplate. The southern boundary of the QCF is marked by the complex Pacific–North American–Explorer

off the coast of southern

British Columbia British Columbia is the westernmost Provinces and territories of Canada, province of Canada. Situated in the Pacific Northwest between the Pacific Ocean and the Rocky Mountains, the province has a diverse geography, with rugged landscapes that ...

. The Queen Charlotte Fault continues northward along the

n 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 In physics, kinematics studies the geometrical aspects of motion of physical objects independent of forces that set them in motion. Constrained motion such as linked machine parts are also described as kinematics. Kinematics is concerned with s ...

parameters. From north to south, there is a decreasing rate of

convergence Convergence may refer to: Arts and media Literature *''Convergence'' (book series), edited by Ruth Nanda Anshen *Convergence (comics), "Convergence" (comics), two separate story lines published by DC Comics: **A four-part crossover storyline that ...

and change in fault obliquity which appears to divide the fault into at least three distinct kinematic zones along strike with associated changes in seafloor morphology, fault structure, and

seismicity Seismicity is a measure encompassing earthquake occurrences, mechanisms, and magnitude at a given geographical location. As such, it summarizes a region's seismic activity. The term was coined by Beno Gutenberg and Charles Francis Richter in 194 ...

. The northern, central, and southern segments with maximum obliquity (approximately 15°–20°) occur south of 53.2°N, and minimum obliquity (less than 5°) occurs north of 56°N. Existing

geophysical Geophysics () is a subject of natural science concerned with the physical processes and properties of Earth and its surrounding space environment, and the use of quantitative methods for their analysis. Geophysicists conduct investigations acros ...

data suggest abrupt transitions in deformation mechanisms and plate boundary dynamics across these boundaries with incipient underthrusting and

strain partitioning In structural geology, strain partitioning is the distribution of the total strain experienced on a rock, area, or region, in terms of different strain intensity and strain type (i.e. pure shear, simple shear, dilatation). This process is observ ...

in the south along Haida Gwaii, distributed transpression in the central segment, and highly localized strike-slip deformation in the north. There are various mechanisms proposed to accommodate oblique convergence along the QCF, including underthrusting, strain partitioning, crustal thickening, and distributed shear. Through geologic time, a change in Pacific plate motion beginning as recently as approximately 6 Ma or as early as approximately 12 Ma caused an increase in convergence along the entire length of the fault and initiated underthrusting along the southern segment where convergence is highest, a process that ultimately led to the 2012 Haida Gwaii thrust earthquake.

Crustal deformation along strike

Southern segment

Crustal deformation Orogeny () is a mountain-building process that takes place at a convergent plate margin when plate motion compresses the margin. An or develops as the compressed plate crumples and is uplifted to form one or more mountain ranges. This involv ...

via

likely dominates the southern segment, as evidenced by the

thrust Thrust is a reaction force described quantitatively by Newton's third law. When a system expels or accelerates mass in one direction, the accelerated mass will cause a force of equal magnitude but opposite direction to be applied to that ...

mechanism of the

2012 Haida Gwaii earthquake The 2012 Haida Gwaii earthquake occurred just after . The shock had a moment magnitude scale, moment magnitude of 7.8 and a maximum Mercalli intensity scale, Mercalli Intensity of V (''Moderate''). The earthquake's epicentre was on Moresby Isla ...

, where geoscientists observed downwarping and

normal fault In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...

ing on the Pacific plate west of

. This hypothesis is also supported by the

morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines *Morphology (archaeology), study of the shapes or forms of artifacts *Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies, ...

of the Queen Charlotte Terrace, a deformed accretionary-prism-like complex west of the main QCF trace. Several recent studies based on

GPS The Global Positioning System (GPS) is a satellite-based hyperbolic navigation system owned by the United States Space Force and operated by Mission Delta 31. It is one of the global navigation satellite systems (GNSS) that provide geol ...

observations of coseismic and postseismic deformation, and thermal modeling support the presence of a shallow plate boundary thrust.

Central segment

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

ridge A ridge is a long, narrow, elevated geomorphologic landform, structural feature, or a combination of both separated from the surrounding terrain by steep sides. The sides of a ridge slope away from a narrow top, the crest or ridgecrest, wi ...

s and

basins Basin may refer to: Geography and geology * Depression (geology) ** Back-arc basin, a submarine feature associated with island arcs and subduction zones ** Debris basin, designed to prevent damage from debris flow ** Drainage basin (hydrology), ...

west of the QCF main trace. There is a distinct structural transition due to a change in the stress regime from

pure shear In mechanics and geology, pure shear is a three-dimensional homogeneous flattening of a body. It is an example of irrotational strain in which body is elongated in one direction while being shortened perpendicularly. For soft materials, such as r ...

in the southern QCF segment to

simple shear Simple shear is a deformation in which parallel planes in a material remain parallel and maintain a constant distance, while translating relative to each other. In fluid mechanics In fluid mechanics, simple shear is a special case of deforma ...

in the central QCF segment as a result of convergence decreasing below a critical angle of approximately 15°.

Northern segment

In the northern segment, which bore the

epicenter The epicenter (), epicentre, or epicentrum in seismology is the point on the Earth's surface directly above a hypocenter or focus, the point where an earthquake or an underground explosion originates. Determination The primary purpose of a ...

of the

strike-slip In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...

2013 Craig earthquake,

bathymetric Bathymetry (; ) is the study of underwater depth of ocean floors ('' seabed topography''), river floors, or lake floors. In other words, bathymetry is the underwater equivalent to hypsometry or topography. The first recorded evidence of water ...

data suggests that the ridge-basin complex gives way to simpler fault morphology. Deformation largely occurs on what appears to be a single strike-slip structure. The same location also marks

earthquake rupture In seismology, an earthquake rupture is the extent of slip that occurs during an earthquake in the Earth's crust. Earthquakes occur for many reasons that include: landslides, movement of magma in a volcano, the formation of a new fault, or, mos ...

boundaries between the 2013 Craig event and the 1972 M7.6 Sitka event, as well as the inferred intersection of the

Chatham Strait Chatham Strait, or Shee ya xhaak in the Tlingit language, is a narrow passage of the Alexander Archipelago in the southeastern region of the U.S. state of Alaska. It separates Chichagof Island and Baranof Island to its west from Admiralty Islan ...

Fault and the Aja

Fracture Zone A fracture zone is a linear feature on the ocean floor—often hundreds, even thousands of kilometers long—resulting from the action of offset mid-ocean ridge axis segments. They are a consequence of plate tectonics. Lithospheric plates on eit ...

(FZ) with the Queen Charlotte Fault; the Aja FZ also marks a 3-million-year contrast in Pacific plate crustal age. Accommodation of strike-slip plate motion along a narrow deformation zone is consistent with

focal mechanism The focal mechanism of an earthquake describes the Fault (geology)#Slip.2C heave.2C throw, deformation in the Hypocenter, source region that generates the seismic waves. In the case of a Fault (geology), fault-related event, it refers to the ori ...

s determined for the Craig event and its

aftershock In seismology, an aftershock is a smaller earthquake that follows a larger earthquake, in Epicenter, the same area of the Mainshock, main shock, caused as the displaced Crust (geology), crust adjusts to the effects of the main shock. Large earthq ...

s. 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 An earthquakealso called a quake, tremor, or tembloris the shaking of the Earth's surface resulting from a sudden release of energy in the lithosphere that creates seismic waves. Earthquakes can range in intensity, from those so weak they c ...

Significant earthquakes along the fault

Six large earthquakes have occurred along the Queen Charlotte Fault within the last hundred years: a

magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...

7 event in 1929, a magnitude 8.1 in 1949 (Canada's largest recorded earthquake since the

1700 Cascadia earthquake 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 P ...

), 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. The P nodal

for the 1949 earthquake indicates a virtually pure

movement with a northwest-striking nodal plane corresponding to the

strike Strike may refer to: People *Strike (surname) * Hobart Huson, author of several drug related books Physical confrontation or removal *Strike (attack), attack with an inanimate object or a part of the human body intended to cause harm * Airstrike, ...

of the fault. This is similar to the 1970 earthquake, which also showed a strike-slip movement with a small but significant

component, consistent with relative plate motion. The 1949 earthquake was larger than the

1906 San Francisco earthquake At 05:12 AM Pacific Time Zone, Pacific Standard Time on Wednesday, April 18, 1906, the coast of Northern California was struck by a major earthquake with an estimated Moment magnitude scale, moment magnitude of 7.9 and a maximum Mercalli inte ...

, causing a nearly segment of the Queen Charlotte Fault to break. The 1958 earthquake had a magnitude of 7.8 and led to a major

landslide Landslides, also known as landslips, rockslips or rockslides, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, mudflows, shallow or deep-seated slope failures and debris flows. Landslides ...

Lituya Bay Lituya Bay (; Tlingit language, Tlingit: ''Ltu.aa'',. Spelled L'tua in translation of Tebenkov's log. meaning 'lake within the point') is a fjord located on the coast of the south-east part of the U.S. state of Alaska. It is long and wide at ...

, Alaska. This resulted in a tsunami that crashed into a mountainside, the largest tsunami run-up ever recorded. The 2012 magnitude 7.8 earthquake struck off the western coast of

at around 8:10pm Pacific Time on Saturday, 27 October. This was the biggest quake in Canadian territory since 1949. Aftershocks as large as magnitude 6.3 were reported. A tsunami was reported locally. Alerts were sent across the Pacific Basin. This earthquake did not have any major impacts, except for the temporary desiccation of the hot springs on Hotspring Island. The springs seemed to have returned to borderline-normal functioning as of July 2014. The 2012 quake was remarkable for having been a

, rather than

, tremor, more like the mechanism of the

to the south. Recent detailed seafloor mapping has revealed the expression of the Queen Charlotte Fault on the seafloor, including the truncation of

submarine canyon A submarine canyon is a steep-sided valley cut into the seabed of the continental slope, sometimes extending well onto the continental shelf, having nearly vertical walls, and occasionally having canyon wall heights of up to , from canyon flo ...

s that occur along the

continental slope A continental margin is the outer edge of continental crust abutting oceanic crust under coastal waters. It is one of the three major zones of the ocean floor, the other two being deep-ocean basins and mid-ocean ridges. The continental margi ...

References

External links

Queen Charlotte-Fairweather Fault System – Alaska Earthquake Information Center
{{coord missing, Pacific Ocean Seismic faults of Canada Seismic zones of British Columbia Geology of the Pacific Ocean Coast of British Columbia Strike-slip faults Supershear earthquakes Oceanography of Canada