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TitleExamining temporal variations in coda Q attenuation before and after some significant Canadian earthquakes: the 2017 resolute earthquake (Mw 6.1) in Nunavut, Canada
AuthorFarahbod, A; Cassidy, J FORCID logo
SourceSeismological Society of America, Proceedings vol. 93, no. 2B, 2022 p. 1237
Alt SeriesNatural Resources Canada, Contribution Series 20210548
PublisherSeismological Society of America
MeetingSeismological Society of America Technical Sessions; Bellevue; US; April 19-23, 2022
Mediapaper; on-line; digital
File formatpdf
NTS58F/11; 58F/12; 58F/13; 58F/14
Lat/Long WENS -96.0000 -94.0000 75.0000 74.5000
Subjectstectonics; earthquakes
ProgramPublic Safety Geoscience Assessing Earthquake Geohazards
Released2022 04 19
AbstractSeveral recent studies around the world indicate temporal variations in coda Q attenuation before and after significant earthquakes. In this study, we examine potential temporal changes in coda Q values for a number of significant Canadian earthquakes in different tectonic environments, including the 2017 M6.1 Resolute earthquake along the northern margin and the M7.8 Haida Gwaii subduction earthquake on Canada's west coast. We calculate coda Q attenuation values before and after the January 8, 2017 Mw 6.1 Resolute earthquake, 8 degrees north of the Arctic circle in Nunavut, on the basis of the Aki's single backscattering model. Waveforms from 100 earthquakes (2.0 = M = 4.6) in almost 24 years before the mainshock and 66 events (mainly aftershocks) in about 4 years after the mainshock recorded by the only nearby seismic station of the Canadian National Seismic Network (CNSN) were utilized. Based on our analysis, overall average of Q0 (Q at 1 Hz) decreased from 89 (before the mainshock) to 83. The most significant decrease in the frequency range between 2 and 16 Hz is observed for areas corresponding to ellipse parameter a2 of 50, 70 and 80 mainly related to aftershock activity. Precursory Q changes were not detectable before the mainshock due to the lack of reported seismicity within 100 km of the recording seismic station for almost 2 years from April 2015 to January 2017. These results are in agreement with other global studies that show a decrease in Q0 following a major earthquake, likely the result of increased fracturing and fluids.
Summary(Plain Language Summary, not published)
Some recent international studies suggest that seismic wave attenuation may change before, during or after large earthquakes. This could be caused by fluids or fractures in the vicinity of faults. Asa part of our national mapping of seismic wave attenuation (coda Q) we are looking at possible temporal changes in attenuation before and after some significant Canadian earthquakes. In this presentation we show observed temporal changes before and after a M6.1 earthquake in the Canadian Arctic. We see a decrease in coda Q (higher wave attenuation) following the earthquake, consistent with increased fluids or fracturing. This is the first of a number of Canadian earthquakes to be studied.

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