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TitleThe 2015 Canada Day, Mw 3.8, earthquake in Nova Scotia
AuthorBent, A L; Peci, V; Halchuk, S
SourceSeismological Research Letters vol. 87, no. 5, 2016 p. 1224-1231,
Alt SeriesEarth Sciences Sector, Contribution Series 20160009
PublisherSeismological Society of America (SSA)
Mediapaper; on-line; digital
File formatpdf; html
ProvinceNova Scotia; Eastern offshore region; New Brunswick
NTS20O/01; 20O/02; 20O/07; 20O/08; 20O/09; 20O/10; 20O/15; 20O/16; 20P; 21A; 21B/01; 21B/02; 21B/07; 21B/08; 21B/09; 21B/10; 21B/15; 21B/16
AreaBay of Fundy; Yarmouth; Shelburne; Liverpool; Digby; Atlantic Ocean
Lat/Long WENS -67.5000 -64.0000 45.0000 43.0000
Subjectsgeophysics; structural geology; seismology; earthquakes; earthquake foci; structural features; faults, thrust; earthquake mechanisms; modelling; seismic waves; p waves; synthetic seismograms
Illustrationslocation maps; tables; sketch maps; seismograms; focal mechanisms
ProgramCanadian Hazard Information Service
Released2016 08 10
AbstractOn 1 July 2015, a magnitude (MN, Mw) 3.8 earthquake occurred north of Yarmouth in southwestern Nova Scotia, a region of extremely low seismicity. Prior to this event, only five earthquakes had been recorded within 50 km of its epicenter since 2000. The earthquake caused no damage but was widely felt in southwestern Nova Scotia with nearly 600 people filling out the Geological Survey of Canada's online "Did You Feel It?" form. Good-quality regional seismograms enabled us to determine the source parameters of the earthquake. The focal mechanism determined by a regional centroid moment tensor inversion is indicative of oblique-thrust faulting. We believe this to be the first focal mechanism solution for a Nova Scotian earthquake. It is consistent with those of earthquakes in the neighboring regions of New Brunswick and Maine and with the regional stress field. Depths were obtained by the moment tensor inversion and by regional depth phase modeling, with consistent results indicative of a focal depth of 9-10 km. The Mw 3.8 is larger than average based on the MN value but within the range of previous observations for eastern Canada. A magnitude (MN) 2.2 aftershock occurred ?7 min after the mainshock but was not reported as felt. A focal depth of 8 km was obtained via the regional depth phase method. The focal mechanism of the aftershock was not determined directly, but a comparison of the waveforms to those of the mainshock suggests a similar source.
Summary(Plain Language Summary, not published)
While small, the magnitude 3.8 earthquake that occurred on Canada Day (1 July) 2015 is of scientific interest because it occurred in a region of extremely low seismic activity. The earthquake was well recorded by the Canadian National Seismograph Network, allowing us to determine its depth, focal mechanism and moment magnitude. While we have no previous focal mechanisms for Nova Scotian earthquakes, the oblique thrust mechanism is similar to earthquakes in New Brunswick, Maine and offshore. Nearly 600 people filled out an online "Did You Feel It" survey, which provides information about the felt effects of the earthquake and a reference for calibrating historical earthquakes.

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