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Temporal Clustering of Earthquakes in the Canadian Arctic on a Regional Scale

Description: 

There has long been a perception that Arctic Canada experiences periods of enhanced seismicity on a regional scale. Following the 2017 M_W 5.9 Barrow Strait earthquake, which preceded a period of apparent enhanced activity, a preliminary attempt was made to determine whether there was any statistical significance to back up these observations (Bent et al., 2018, SRL). This earlier analysis, covering a time period of twenty-five years, found evidence for statistical significance. The current study expands on that work using a sixty year earthquake catalog extending back to the mid-1960s when a national seismograph network was established in Canada. Prior to that, the catalog for the Arctic region is not complete enough for reliable statistics. The raw data show several periods where the occurrence of moderately large earthquakes is significant at the 2-3 sigma level. Whether earthquake catalogs should be declustered for seismic hazard assessment is a subject of debate but declustering is useful in separating events for which there is a known or at least strongly suspected causal relation, such as aftershocks and swarms, from those with no expected relation. When declustering is undertaken, the statistical evidence for enhanced seismicity remains. Although a viable physical mechanism to explain the regional clustering has yet to be established, several possibilities can be ruled out. The earthquakes analyzed are all below M_W 6.0 and separated by 100s of km, suggesting that stress transfer on nearby faults is not the cause. Dynamic triggering from distant earthquakes can also be eliminated. Incidentally, dynamic triggering is also ruled out as the generating mechanism for swarms, whose cause has also not been established. There is no evidence for an overall increase in seismic activity in the Canadian north. The periods of increased activity tend to be short, 1 to 2 years in duration, after which the seismicity returns to its background level.

Session: Deciphering Earthquake Clustering for the Better Understanding of Crustal Deformation Mechanisms [Poster]

Type: Poster

Date: 4/20/2023

Presentation Time: 08:00 AM (local time)

Presenting Author: Allison L. Bent

Student Presenter: No

Invited Presentation: 

Authors