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TitleRegional seismic wave propagation (Lg & Sn phases) in the Amerasia Basin and High Arctic
AuthorChiu, K; Snyder, D B
SourcePolar Science vol. 9, 2015 p. 130-145, (Open Access)
Alt SeriesEarth Sciences Sector, Contribution Series 20140097
PublisherElsevier BV
Mediapaper; on-line; digital
File formatpdf
ProvinceNunavut; Northwest Territories; Yukon; Offshore region
NTS15; 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
Areaarctic; 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
Subjectstectonics; geophysics; wave propagation; continental crust; seismic refraction surveys; earthquakes; oceanic crust; Amerasia Basin; Lg propagation; receiver function studies
Illustrationslocation maps; tables; seismic reflection profiles; schematic diagrams
ProgramDelineating Canada's Continental Shelf Under UNCLOS, Preparation of a submission for an extended continental shelf in the Atlantic and Arctic Oceans under UNCLOS
AbstractObservation 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.