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.
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, 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]
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]
Northern segment
In the northern segment, which bore the
epicenter of the
strike-slip2013 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.
The
P nodalfocal 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]
^Bird, Alison L.; Cassidy, John F.; Kao, Honn; Leonard, Lucinda J.; Allen, Trevor I.; Nykolaishen, Lisa; Dragert, Herb; Hobbs, Tiegan E.; Farahbod, Amir M. (2016-02-01),
"The October 2012 magnitude (Mw) 7.8 earthquake offshore Haida Gwaii, Canada", Summary of the Bulletin of the International Seismological Centre, July - December 2012, Volume 49, Issue 7-12, Thatcham, UK: International Seismological Centre, pp. 41–72,
doi:
10.5281/zenodo.999242,
S2CID199107488, retrieved 2021-11-24
^Bérubé, J., G. C. Rogers, R. M. Ellis, and F. O. Hasselgren (1989). A microseismicity survey of the Queen Charlotte Islands region, Can. J. Earth Sci. 26, 2556–2566
^Barrie, J.V., Conway, K., Harris, P.T., 2013. The Queen Charlotte Fault, British Columbia: seafloor anatomy of a transform fault and its influence on sediment processes. Geo-Marine Letters 33, 311–318.
^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.