| Title | Moment magnitude (MW) conversion relations for use in hazard assessment in offshore eastern Canada |
| Download | Downloads |
| |
| Licence | Please note the adoption of the Open Government Licence - Canada
supersedes any previous licences. |
| Author | Bent, A L |
| Source | Geological Survey of Canada, Open File 8027, 2016, 12 pages, https://doi.org/10.4095/297965  Open Access |
| Image |  |
| Year | 2016 |
| Publisher | Natural Resources Canada |
| Document | open file |
| Lang. | English |
| Media | on-line; digital |
| File format | pdf |
| Province | Ontario; Quebec; Newfoundland and Labrador; Nunavut; Eastern offshore region |
| NTS | 1; 2; 3; 10; 11; 12; 13; 14; 15; 16; 20; 21; 22; 23; 24; 25; 26; 27; 28; 29; 30; 31; 32; 33; 34; 35; 36; 37; 38; 39; 42; 43; 44; 45; 46; 47; 48; 49; 120; 340 |
| Lat/Long WENS | -95.0000 -45.0000 85.0000 40.0000 |
| Subjects | geophysics; earthquakes; earthquake studies; earthquake magnitudes; earthquake foci; seismographs; seismicity; seismic velocities |
| Illustrations | location maps; graphs; plots; tables |
| Program | Canadian Hazard Information Service |
| Released | 2016 05 03 |
| Abstract | Seismic hazard assessments based heavily on earthquake recurrence rates require that the same magnitude scale be used for all earthquakes evaluated to ensure that the assessment is unbiased and uniform
across the area of interest no matter how large. Moment magnitude, MW, is generally seen as the magnitude of preference in current practice. However, it was not routinely calculated in the past for earthquakes in Canada, necessitating the conversion
from other magnitude types in common use. This paper focuses on the offshore regions of eastern Canada, including the eastern Arctic, where ML is the day-to-day magnitude scale. Conversions to MW are established and evaluated. Until very recently
there were few MW values determined for offshore earthquakes. In recent years, however, regional centroid moment tensor inversions have been run on a routine basis for earthquakes in this region allowing us to build up a database of moment magnitudes
for the offshore. While the dataset is still smaller than for the adjacent onshore regions and somewhat restricted in magnitude range, it has enabled the development of an ML-MW conversion relation for offshore eastern Canada, which shows that, on
average, ML is 0.21 magnitude units greater than MW. Statistical tests show no advantage to using a linear relation over a straight constant conversion. |
| Summary | (Plain Language Summary, not published)
Seismic hazard assessments require that the same magnitude scale be used for all earthquakes evaluated to ensure that the assessment is unbiased and
uniform across the area of interest. Moment magnitude, MW, is the magnitude of preference in current practice. Conversion relations must be established for the many magnitude scales in common use. This paper focuses on the offshore regions of
eastern Canada where ML is the day-to-day magnitude scale. Conversions to MW are established and evaluated. Until very recently there were few MW values determined for offshore earthquakes. In recent years, however, regional centroid moment
tensor inversions have been run on a routine basis for moderate and large earthquakes in this region allowing us to build up a database of moment magnitudes for the offshore. While the dataset is still small and somewhat restricted in magnitude
range, it has enabled the development of an ML-MW conversion relation for offshore eastern Canada, which shows that, on average, ML is 0.21 magnitude units greater than MW. |
| GEOSCAN ID | 297965 |
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