The Queen Charlotte Fault is an active transform fault that marks the boundary of the North American plate and the

Pacific plate The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At , it is the largest tectonic plate. The plate first came into existence 190 million years ago, at the triple junction between the Farallon, Phoenix, and Iza ...

. It is Canada's right-lateral strike-slip equivalent to the San Andreas Fault to the south in California. The Queen Charlotte Fault forms a triple junction south with the Cascadia subduction zone 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 Faul ...

). 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 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 Pa ...

) in terms of slip rates and seismogenic potential. It sustains the highest known deformation rates among continental or continent-ocean transform systems globally, accommodating greater than 50mm/yr

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 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. 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. 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. Th ...

, an oceanic plateau and microplate. The southern boundary of the QCF is marked by the complex Pacific–North American–Explorer triple junction off the coast of southern British Columbia. 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 Kinematics is a subfield of physics, developed in classical mechanics, that describes the motion of points, bodies (objects), and systems of bodies (groups of objects) without considering the forces that cause them to move. Kinematics, as a fie ...

parameters. From north to south, there is a decreasing rate of convergence 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. 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 Strain partitioning is commonly referred to as a deformation process in which the total strain experienced on a rock, area, or region, is heterogeneously distributed in terms of the strain intensity and strain type (i.e. pure shear, simple shear, ...

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, this include underthrusting and 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 via strain partitioning likely dominates the southern segment as evidenced by the thrust mechanism of the 2012 Haida Gwaii earthquake, observed downwarping and normal faulting on the pacific plate west of Haida Gwaii. This is also supported by the morphology of the Queen Charlotte Terrace, an approximately 30 km wide deformed

accretionary prism An accretionary wedge or accretionary prism forms from sediments accreted onto the non-subducting tectonic plate at a convergent plate boundary. Most of the material in the accretionary wedge consists of marine sediments scraped off from the do ...

-like complex west of the main QCF trace. Several recent studies based on seismicity,

GPS The Global Positioning System (GPS), originally Navstar GPS, is a Radionavigation-satellite service, satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of t ...

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 or a mountain ridge is a geographical feature consisting of a chain of mountains or hills that form a continuous elevated crest for an extended distance. The sides of the ridge slope away from the narrow top on either side. The line ...

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), a ...

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 rub ...

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 deformati ...

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 of the 2013 Craig strike-slip earthquake, bathymetric 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 boundaries between the 2013 Craig event and the 1972 M7.6 Sitka event, as well as the inferred intersection of Chatham Straight 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. Accommodation of strike-slip plate motion along a narrow deformation zone is consistent with

focal mechanism The focal mechanism of an earthquake describes the deformation in the source region that generates the seismic waves. In the case of a fault-related event it refers to the orientation of the fault plane that slipped and the slip vector and is ...

s determined for the Craig event and

aftershock In seismology, an aftershock is a smaller earthquake that follows a larger earthquake, in the same area of the main shock, caused as the displaced crust adjusts to the effects of the main shock. Large earthquakes can have hundreds to thousand ...

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 earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, from ...

Significant earthquakes along the fault

Five large earthquakes have occurred along the Queen Charlotte Fault within the last hundred years: a magnitude 7 event in 1929, a magnitude 8.1 occurred 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, and a magnitude 7.8 on Oct 27 2012 The P nodal

for the 1949 earthquake indicates a virtually pure strike-slip movement with a northwest striking nodal plane corresponding to the strike of the fault. The 1970 earthquake did however show a similar 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 At 05:12 Pacific Standard Time on Wednesday, April 18, 1906, the coast of Northern California was struck by a major earthquake with an estimated moment magnitude of 7.9 and a maximum Mercalli intensity of XI (''Extreme''). High-intensity sha ...

, 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 feet tsunami that crashed into a mountainside, the largest recorded tsunami run up. A 7.8 magnitude quake struck off the western coast of Haida Gwaii at around 8:10pm Pacific Time on Saturday 27 October 2012. This was the biggest quake in Canadian territory since 1949. Aftershocks as large as 6.3 were reported. A 45-cm tsunami was reported locally. Alerts were sent across the Pacific Basin. This earthquake did not have any major impacts, except for the temporary cessation of the hotsprings on

Hotspring Island Hotspring Island, originally named in English as Volcanic Island and known in the Haida language as G̱andll K'in Gwaayaay ("Hot-Water-Island"), is a small island near the southeast coast of Lyell Island in the Haida Gwaii archipelago of the North ...

. The spring seems to have returned to borderline nominal functioning as of July 2014. This quake was remarkable for having been a thrust, and not a

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 ...

tremor, more like the mechanism of the Cascadia Subduction Zone to the south. Recent detailed seafloor mapping has revealed the expression of the Queen Charlotte Fault on the seafloor including the truncation of submarine canyons that occur along the continental slope.Harris, P.T., Barrie, J.V., Conway, K.W., Greene, G.H., 2014. Hanging canyons of Haida Gwaii, British Columbia, Canada: Fault-control on submarine canyon geomorphology along active continental margins. Deep-Sea Research Part II: Topical Studies in Oceanography 104, 83–92.

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