| Title | Structure 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 |
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| Author | Bent, A L; Kao, H ; Darbyshire, F |
| Source | 2019 Annual Meeting, Seismological Society of America, technical sessions; Seismological Research Letters vol. 90, no. 2B, 2019 p. 950, https://doi.org/10.1785/0220190061 |
| Links | Online - En ligne (complete volume - volume
complet, PDF, 4.24 MB)
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| Image |  |
| Year | 2019 |
| Alt Series | Natural Resources Canada, Contribution Series 20190047 |
| Publisher | Seismological Society of America (SSA) |
| Meeting | 2019 Annual Meeting of the Seismological Society of America; Seattle, WA; US; April 23-26, 2019 |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf (Adobe® Reader®) |
| Province | Quebec |
| NTS | 12E; 12F; 12K; 12L; 21L; 21M; 21N; 22A; 22B; 22C; 22D; 22F; 22G; 22H; 22I; 22J |
| Area | St. Lawrence River; Gulf of St. Lawrence |
| Lat/Long WENS | -72.0000 -60.0000 51.0000 46.0000 |
| Subjects | geophysics; 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 |
| Program | Public Safety Geoscience Assessing Earthquake Geohazards |
| Released | 2019 03 20 |
| Abstract | The 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. |
| GEOSCAN ID | 314652 |
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