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TitleStation magnitude corrections ad related issues for eastern Canada
AuthorBent, A L
SourceGeological Survey of Canada, Open File 6505, 2010, 36 pages, (Open Access)
PublisherNatural Resources Canada
Documentopen file
Mediaon-line; digital
File formatpdf
ProvinceNewfoundland and Labrador; Nova Scotia; New Brunswick; Prince Edward Island; Quebec; Ontario; Manitoba; Nunavut
NTS1; 2; 11; 12; 13; 14; 21; 22; 23; 24; 25; 26; 27; 30; 31; 32; 33; 34; 35; 36; 37; 40; 41; 42; 43; 44; 45; 46; 47; 52; 53; 54; 55; 56; 62A; 65; 66; 75; 76; 86; 87
Lat/Long WENS-116.0000 -50.0000 71.0000 40.0000
Subjectsgeophysics; earthquakes; earthquake magnitudes; earthquake studies; earthquake risk; earthquake foci; seismographs; seismology; seismological network
Illustrationstables; plots
Natural Resources Canada Library - Ottawa (Earth Sciences)
ProgramCanadian Hazard Information Service, Canadian Hazard Information Service
Released2010 05 20
AbstractEarthquake magnitudes are generally defined as an average (most often, the arithmetic mean) of magnitudes calculated at many individual seismograph stations. While some variation in station magnitudes stems directly from the seismic source (for example, radiation pattern or directivity) conditions beneath the recording station also affect the calculated value. For example, soft soils tend to amplify the seismic signal resulting in an apparent magnitude that is higher than the true value. By analyzing the differences between the magnitude determined at a specific station and the average magnitude for a large number of earthquakes, a site correction for the station can be determined. The intent of this study is to determine the station corrections for those seismographs routinely used in the calculations of magnitudes in eastern Canada. Corrections are determined for both the mN and ML magnitude scales. Additionally the magnitude residuals were further evaluated to determine whether they were dependent on parameters such as distance, azimuth or frequency. The effects of azimuth and frequency appear to be minimal. There does appear to be a distance dependency suggesting that the attenuation relation used in the magnitude calculation may need to be modified. Finally, several issues relating to magnitudes are raised, the resolution of which are beyond the intended scope of this paper.