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TitleIntraplate seismicity of a recently deglaciated shield terrane: a case study from northern Ontario, Canada
AuthorMa, S; Eaton, D W; Adams, J
SourceBulletin of the Seismological Society of America, 2008 p. 2828-2848,
Alt SeriesEarth Sciences Sector, Contribution Series 20070590
Mediapaper; on-line; digital
File formathtml; pdf (Adobe® Reader®)
ProvinceOntario; Manitoba
NTS31L; 31M; 32D; 32E; 32L; 32M; 33D; 33E; 33L; 33M; 34D; 41I; 41J; 41K; 41L; 41M; 41N; 41O; 41P; 42; 43; 44A; 44B; 44C; 44D; 52; 53; 54A; 54B; 54C; 54D; 62A; 62H; 62I; 62P; 63A; 63H; 63I; 63P; 64A
Areanorthern Ontario; James Bay; Kapuskasing; Lake Superior; Dryden; Severn Highlands; Sudbury; Lake Nipigon; Geraldton; Canada; United States
Lat/Long WENS-98.0000 -79.0000 57.0000 46.0000
Subjectsgeophysics; tectonics; seismology; seismicity; earthquakes; earthquake studies; earthquake catalogues; earthquake foci; geological history; glacial history; deglaciation; seismic waves; surface wave studies; p waves; earthquake risk; mining activities; seismic velocities; Archean; terranes; mantle; rheology; structural controls; structural features; faults; faults, thrust; isostasy; isostatic rebound; Canadian Shield; Superioir Province; precambrian shield; focal depth solutions; Precambrian
Illustrationssketch maps; histograms; models; spectra; tables; focal mechanisms
ProgramCanadian Hazard Information Service
ProgramNSERC Natural Sciences and Engineering Research Council of Canada
LinksSupplementary Data - Données supplémentaires
AbstractThe economy of northern Ontario, Canada is heavily dependent on mining, so accurate knowledge of seismicity is important for the safe design and operation of mines and other critical facilities, including a proposed underground repository for nuclear waste. In this study, we analyzed 537 cataloged earthquakes that occurred from 1980 to 2006. Seismicity is mainly concentrated in topographically-elevated Archean terranes northwest of Lake Superior, and in the James Bay and Kapuskasing regions. We analyzed waveforms to determine focal depth for 331 recorded events, using the regional depth phase modeling (RDPM) method coupled with surface-wave relative-amplitude analysis. The majority of events are shallow (<6 km) and concentrated in areas of relatively high elevation (>300 m), although in the eastern part this pattern breaks down and some deeper earthquakes (>12km) are observed. Based on a moving-window event-counting technique, we show that distinct spatial clusters of seismicity can be delineated that are statistically significant relative to background seismicity levels. A particularly active cluster is located within James Bay, where focal depths range from a few km to more than 20 km. Another cluster near Kapuskasing contains deep-focus events, and may occur along a hotspot track that runs through western Quebec. Near Dryden, a shallow (~1 km) earthquake swarm concentrated in a 1 km × 1 km region commenced in May 2002, faded, and then started up again in February 2003. Shallow mining-induced events are also common around Sudbury, a major world center for nickel mining. The overall pattern of seismicity appears to correlate with upper mantle P-wave velocity anomalies, but does not appear to correlate with ice load during the last glacial maximum. This suggests that lateral variations in mantle rheology may play a significant role in controlling intraplate seismicity of shield areas.