An Overview of the 28 October 2012 Mw 7.7 Earthquake in Haida Gwaii, Canada: A Tsunamigenic Thrust Event Along a Predominantly Strike-Slip Margin

Cassidy, John F.; Rogers, Garry C.; Hyndman, R. D.

doi:10.1007/s00024-014-0775-1

Cited by 38 publications

(30 citation statements)

References 27 publications

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“…Moreover, the 2012 Haida Gwaii aftershock distribution overlaps the southern part of the estimated rupture zone of the 1949 M 8.1 Queen Charlotte earthquake (Rogers, 1986;Cassidy et al, 2014). Rogers (1986) reported that a seismic gap exists between the southern boundary of the 1949 Queen Charlotte and the northern end of the 1970 M 7.4 Cape St. James earthquake.…”

Section: Discussionmentioning

confidence: 96%

“…The tectonic setting of this region is characterized by a major transform plate boundary between the Pacific and North American plates (i.e., the Queen Charlotte fault [QCF]), along which the 1949 M s 8.1 earthquake took place (Rogers, 1983;Bostwick, 1984). Although the source region of the more recent event (the 28 October 2012 M w 7.8 Haida Gwaii earthquake) overlaps the southern portion of the 1949 rupture, the corresponding seismogenic pattern is obviously different in the form of a thrust-faulting mechanism (Lay et al, 2013;Cassidy et al, 2014;Kao et al, 2015).…”

Section: Introductionmentioning

confidence: 98%

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Spatiotemporal Distribution of Events during the First Week of the 2012 Haida Gwaii Aftershock Sequence

Farahbod

Kao

2015

Bulletin of the Seismological Society of America

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We systematically relocated the 2012 Haida Gwaii aftershock sequence by re-examining continuous seismic waveforms of the Canadian National Seismographic Network (CNSN). Because of the sparse station density in the source area and the offshore location of the majority of events, precise determination of hypocenters is extremely challenging. Constraints on the back azimuth and incident angle of ray paths were derived from the cross correlation of three-component waveforms and incorporated into the locating process to improve the results. We located 1228 aftershocks for the first week after the mainshock, effectively double the size of the CNSN routine earthquake catalog. The distribution of aftershocks tends to form two linear trends roughly parallel to the strike of the plate margin in the northwest-southeast direction. The trend located updip from the mainshock within the subducting Pacific plate appears to have three clusters spanning a lateral distance of ∼80 km. The other trend coincides with the surface trace of the Queen Charlotte fault (QCF), spanning the northern two-thirds of the main rupture zone. The overall area of aftershock distribution is ∼120 km × ∼40 km. Aftershocks overlap the southern part of the estimated rupture zone of the 1949 earthquake, with no activity in the seismic gap farther to the south. Therefore, it is likely that the 2012 earthquake only partially released the accumulated stress on the strike-slip transform fault system. In this scenario, the possibility of a major strike-slip earthquake along the southernmost part of the QCF should not be ignored.

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Section: Discussionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 98%

Spatiotemporal Distribution of Events during the First Week of the 2012 Haida Gwaii Aftershock Sequence

Farahbod

Kao

2015

Bulletin of the Seismological Society of America

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“…In 1949, an M s 8.1 strike-slip earthquake occurred on the QCF off the northwest coast of Graham Island (Bostwick, 1984). On 28 October 2012, an M w 7.8 thrust earthquake (Cassidy et al, 2014) occurred off the west coast of Moresby Island producing a large local tsunami (Leonard and Bednarski, 2014). The 2012 earthquake occurred on a shallow northeast-dipping thrust fault rather than the QCF (Cassidy et al, 2014), indicating there are separate faults accommodating strike slip and convergent plate motion, and suggesting oblique subduction at the margin (Fig.…”

Section: Introductionmentioning

confidence: 95%

“…In the south, west of Moresby Island, most earthquakes have thrust mechanisms, but there is no clear evidence of a Wadati-Benioff earthquake zone. Further, these thrust solutions are high angle and do not reside on the main thrust fault of the 2012 event (Cassidy et al, 2014).…”

Section: Introductionmentioning

confidence: 98%

Shear-Wave Velocity Structure in the Vicinity of the 2012 Mw 7.8 Haida Gwaii Earthquake from Receiver Function Inversion

Gosselin

Cassidy

Dosso

2015

Bulletin of the Seismological Society of America

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The thrust mechanism of the 2012 M w 7.8 Haida Gwaii earthquake suggests convergence across the transpressive Pacific-North America plate boundary in the region is accommodated by underthrusting, with important consequences for seismic-and tsunami-hazard analysis. This article investigates the crustal structure and extent of subduction beneath Haida Gwaii by nonlinear inversion of receiver function data processed from teleseismic recordings at five land-based seismograph stations. Three of these stations were deployed since the 2012 earthquake to extend coverage to the southeast and have not been analyzed previously. The inversions provide estimates of the shear-wave velocity structure beneath much of Moresby Island. Results indicate a positive velocity contrast at approximately 18-26 km depth, interpreted as a shallow continental Moho. A 12-17 km thick low shear-wave velocity zone is also identified, which increases in depth from ∼25 to 42 km along the direction of plate convergence, which is interpreted as subducting oceanic material. These results provide the first evidence that the subducting oceanic plate extends beneath the entirety of Moresby Island.

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“…It underlies Haida Gwaii, Hecate Strait, Dixon Entrance, and much of Queen Charlotte Sound. The QCB is part of an active tectonic continental margin and is subject to large earthquakes (Cassidy et al 2014). …”

Section: Introductionmentioning

confidence: 99%

Neogene strontium isotope stratigraphy, foraminifer biostratigraphy, and lithostratigraphy from offshore wells, Queen Charlotte Basin, British Columbia, Canada

et al. 2015

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Strontium isotope ages of foraminifers from Early Miocene to Late Pliocene (Neogene) sequences (21.2-3.4 Ma) are reported for the first time from the Queen Charlotte Basin (QCB) in Queen Charlotte Sound, offshore British Columbia. These ages, together with a revised foraminifer biostratigraphy and log data from two offshore wells, provide a high-resolution chronostratigraphy for the southern part of the QCB. The data show thick 1717-2636 m Miocene sequences overlain by much thinner Pliocene and younger units (<240 m). Assessments of foraminifer biofacies indicate common transported neritic and shelf faunas into slope or bathyal environments where changes in basin water depths indicate significant deformation and erosion. Résumé : Des datations isotopiques (strontium) de foraminifères dans des successions (21,2 à 3,4 Ma) du Miocène précoce auPliocène tardif (Néogène) sont rapportées pour la première fois du bassin de la Reine-Charlotte dans le détroit de la ReineCharlotte, au large de la Colombie Britannique. Ces âges, joints à une biostratigraphie des foraminifères révisée et des données de diagraphies de deux puits au large, fournissent une chronostratigraphie à haute définition pour la partie sud du bassin de la Reine-Charlotte.

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An Overview of the 28 October 2012 Mw 7.7 Earthquake in Haida Gwaii, Canada: A Tsunamigenic Thrust Event Along a Predominantly Strike-Slip Margin

Cited by 38 publications

References 27 publications

Spatiotemporal Distribution of Events during the First Week of the 2012 Haida Gwaii Aftershock Sequence

Spatiotemporal Distribution of Events during the First Week of the 2012 Haida Gwaii Aftershock Sequence

Shear-Wave Velocity Structure in the Vicinity of the 2012 Mw 7.8 Haida Gwaii Earthquake from Receiver Function Inversion

Neogene strontium isotope stratigraphy, foraminifer biostratigraphy, and lithostratigraphy from offshore wells, Queen Charlotte Basin, British Columbia, Canada

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