| Title | Regional seismic wave propagation (Lg & Sn phases) in the Amerasia Basin and High Arctic |
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| Author | Chiu, K; Snyder, D B |
| Source | Polar Science vol. 9, 2015 p. 130-145, https://doi.org/10.1016/j.polar.2014.09.001  Open Access |
| Year | 2015 |
| Alt Series | Earth Sciences Sector, Contribution Series 20140097 |
| Publisher | Elsevier BV |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf |
| Province | Nunavut; Northwest Territories; Yukon; Offshore region |
| NTS | 15; 16; 19; 20; 25; 26; 27; 28; 29; 35; 36; 37; 38; 39; 45; 46; 47; 48; 49; 55; 56; 57; 58; 59; 65; 66; 67; 68; 69; 75; 76; 77; 78; 79; 85; 86; 87; 88; 89; 95; 96; 97; 98; 99; 105; 106; 107; 115; 116; 117;
120; 340; 560 |
| Area | arctic; Denmark; Russian Federation; Svalbard and Jan Mayen; United States of America; Iceland; Norway; Sweden |
| Lat/Long WENS | -180.0000 180.0000 90.0000 60.0000 |
| Subjects | tectonics; geophysics; wave propagation; continental crust; seismic refraction surveys; earthquakes; oceanic crust; Amerasia Basin |
| Illustrations | location maps; tables; seismic reflection profiles; schematic diagrams |
| Program | Delineating Canada's Continental Shelf Under UNCLOS |
| Released | 2015 03 01 |
| Abstract | Observation of Lg seismic waves at regional distances has long been considered indicative of continental crust that is 30e40 km thick. This study updates an earlier assessment of Lg propagation
efficiency to characterize continental or non-continental crust and related structures across the Amerasia Basin and surrounding continental areas of the high Arctic. Recent refraction surveys and receiver function studies provide crustal thickness
estimates of 18e41 km for comparison. Among 7000 candidate earthquakeestation pairs considered, no classic Lg phases (0.14e2 Hz) are observed to cross the Amerasia Basin (Canada Basin, Alpha-Mendeleev Ridge) efficiently, but lower frequency
(0.035e0.17 Hz) arrivals with group velocities intermediate between Lg and Sn (sometimes called early Lg) are observed along many ray paths crossing the basin. The characteristic frequencies of these observed arrivals match well with those of
synthetic waves propagated within models with thinned or pinched continental crust, such as crust characteristic of the North Sea, and thus suggest that most parts of the Amerasia Basin have a crustal thickness intermediate between that typical of
thin continental and oceanic crust. |
| Summary | (Plain Language Summary, not published)
The thickness of Earth's crust, as traditionally measured by a seismic discontinuity, the Moho, is historically a strong discriminator between continents
and oceans. UNCLOS criteria for determining continental margins involve water depth and sediment thickness, but a continental or oceanic setting provides important context for decisions by this UN commission. NRCan's UNCLOS program has measured these
various parameters in key Arctic regions, but such surveys are not possible throughout the Canada Basin and Arctic Ocean. Teleseismic Lg waves from regional earthquakes recorded at circum-Arctic stations can use these local crustal thickness
estimates to extrapolate them smoothly across the Arctic Ocean. Lg studies in the 1950's are updated using a denser array of recording stations. The results suggest that few parts of the Arctic Ocean have classic oceanic crustal structure; most
appear to have thinned continental crust such as that of the North Sea. This strengthens arguments for extension of Canada's western Arctic margin and related petroleum potential. |
| GEOSCAN ID | 294804 |
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