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TitreThe McAdam, New Brunswick earthquake swarms of 2012 and 2015-2016: extremely shallow, natural events
AuteurBent, A L; Halchuk, S; Peci, V; Butler, K; Burke, K B S; Adams, J; Dahal, N; Hayek, S
SourceSeismological Research Letters vol. 88, no. 6, 2017 p. 1586-1600, https://doi.org/10.1785/0220170071
Année2017
Séries alt.Ressources naturelles Canada, Contribution externe 20170001
ÉditeurSeismological Society of America
Documentpublication en série
Lang.anglais
DOIhttps://doi.org/10.1785/0220170071
Mediapapier; en ligne; numérique
Formatspdf
ProvinceNouveau-Brunswick
SNRC21F; 21G; 21H; 21I; 21J; 21K; 21N; 21O; 21P
Lat/Long OENS -70.0000 -64.0000 48.0000 45.0000
Sujetssecousses séismiques; sismicité; études séismiques; sismographes; réseau sismique; séismologie; géophysique
Illustrationslocation maps; satellite images; plots; graphs
ProgrammeService d'information sur les dangers naturels au Canada, Service d'information sur les dangers naturels au Canada
Résumé(disponible en anglais seulement)
Beginning in March 2012 inhabitants of McAdam, New Brunswick reported feeling and/or hearing many earthquakes within a 1-2 km2 area of the village. The largest events (MN < 2.6) were recorded by regional seismographs, the closest at that time being 65 km away. Public concern combined with the large number of events and their localization led the Geological Survey of Canada (GSC) to deploy three temporary instruments in McAdam. The University of New Brunswick (UNB) provided a fourth. The instruments remained in place for several months and were then removed as activity had largely died off by June 2012. There was a short resurgence in activity late in 2015 with seven felt events occurring 7-9 December. In February 2016, the swarm activity picked up considerably. In light of the increased activity, which included the largest earthquake of the sequence (MN 3.3 on 9 February 2016) the GSC redeployed four instruments which remained in place for several months until the activity subsided. As of 1 November 2016, 164 earthquakes were located, some by enough stations to allow precise depth determination by one or more methods. All the earthquakes were extremely shallow, 0.0-1.2 km. The majority of epicenters lie in a WNW-ESE trending ellipse. Focal mechanisms determined for a small number of events are largely consistent with northeast-southwest compression and with earthquakes in neighboring regions. Sixty-eight of the events were reported as felt, with several of the felt events being of magnitude (MN or ML) less than 1.0. A strong motion recorder recorded a PGA of 9%g from an MN 1.7 earthquake at about 0.8 km hypocentral distance. There was no human activity that could have induced or triggered the swarm, and the cause remains unexplained. McAdam sits on Silurian metasediments intruded by the granitic Pokiok Batholith exposed just to the NW. No faults are mapped close to McAdam, but the events might have occurred on a NW-SE splay of the Fredericton Fault.
Résumé(Résumé en langage clair et simple, non publié)
Au printemps de 2012 et à nouveau pendant l'hiver de 2016, les habitants de McAdam, au Nouveau-Brunswick, ont ressenti de nombreux tremblements de terre. Cette activité a été identifiée comme un essaim sismique. Bien que très petits, les tremblements de terre ont eu lieu directement sous la communauté. Des stations de sismographe temporaires ont été installées à McAdam pour mieux enregistrer les séismes. La recherche utilisant les données de ces stations ainsi que les stations permanentes à plus grandes distances nous ont permis de déterminer les emplacements et les profondeurs précises de nombreux tremblements de terre, de mécanismes au foyer (orientation et style des failles) et de placer les séismes dans un contexte régional. Les tremblements de terre étaient tous extrêmement superficiels se produisant à des profondeurs de moins de 1,5 km. Nous n'avons pas été en mesure de déterminer ce qui a déclenché l'activité des essaims, mais nous avons écarté les activités humaines, telles que l'exploitation minière et la fracking.
GEOSCAN ID300253