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TitleStructure and anisotropy of the crust and upper mantle along the St. Lawrence corridor, eastern Canada, from the Charlevoix Seismic Zone to the Gulf of St. Lawrence
AuthorBent, A L; Kao, HORCID logo; Darbyshire, F
Source2019 Annual Meeting, Seismological Society of America, technical sessions; Seismological Research Letters vol. 90, no. 2B, 2019 p. 950,
LinksOnline - En ligne (complete volume - volume complet, PDF, 4.24 MB)
Alt SeriesNatural Resources Canada, Contribution Series 20190047
PublisherSeismological Society of America (SSA)
Meeting2019 Annual Meeting of the Seismological Society of America; Seattle, WA; US; April 23-26, 2019
Mediapaper; on-line; digital
File formatpdf (Adobe® Reader®)
NTS12E; 12F; 12K; 12L; 21L; 21M; 21N; 22A; 22B; 22C; 22D; 22F; 22G; 22H; 22I; 22J
AreaSt. Lawrence River; Gulf of St. Lawrence
Lat/Long WENS -72.0000 -60.0000 51.0000 46.0000
Subjectsgeophysics; structural geology; tectonics; seismology; earthquakes; earthquake risk; seismic risk; seismicity; crustal structure; lithosphere; mantle; anisotropy; seismic waves; s waves; seismic velocities; models; seismological network; seismographs; St. Lawrence Platform; Canadian Shield; Appalachian Province; Canadian National Seismograph Network; Charlevoix Seismic Zone; Lower St. Lawrence Seismic Zone; Infrastructures
ProgramPublic Safety Geoscience Assessing Earthquake Geohazards
Released2019 03 20
AbstractThe St. Lawrence corridor in eastern Canada comprises three active seismic zones separated by regions of low seismicity. Understanding the unequal distribution of seismicity has potential implications for hazard assessment of this highly populated region and its critical infrastructure. Despite its intraplate setting, the region is tectonically complex. The St. Lawrence River, underlain by the St. Lawrence Platform, delineates much of the boundary between the Canadian Shield to the north and the Appalachians to the south. To better define the structural complexities of this important region, shear wave velocity models were derived from teleseismic receiver functions for seismograph stations along the St. Lawrence. Gaps in the broadband coverage of the Canadian National Seismograph Network were supplemented by temporary stations deployed for this project and by taking advantage of any other deployments in the region. The current study focuses on the region between the Charlevoix Seismic Zone and the Gulf of St. Lawrence, complementing previous work that covered the region between Charlevoix and Montreal. All stations modeled show a high velocity lid to a depth of ~5km and a Moho at 38-45 km. The structure is consistent from one station to the next. Discontinuities can be correlated allowing for the development of a pseudo-3D model. Evidence for mantle anisotropy is obtained from SKS splitting. Fast-polarization directions are subparallel to the strike of the St. Lawrence valley in the study region and parallel to the valley further west, with a slight rotation of fast orientation from west to east. The average delay time of ~1 second requires an upper-mantle component, which is likely a combination of contributions from 'fossil' lithospheric anisotropy and mineral alignments from present-day sublithospheric mantle flow.
Summary(Plain Language Summary, not published)
The St. Lawrence Corridor of eastern Canada is home to three active seismic zones separated by regions of very low seismicity. The reasons for the differences are not well understood but have potential implications for seismic hazard assessments. Supplementing the national seismograph network with temporary instruments, we model and compare the crustal structure in the active and inactive regions. The current study focuses on the segment from Charlevoix to the Gulf of St. Lawrence and complements a previous on that covered the Charlevoix-Montreal segment. We have developed a 3D model of the entire St. Lawrence corridor, which can be used for improved earthquake locations. We see no strong evidence for structural differences between the active and inactive regions.

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