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TitleEstimating seismic moment magnitude (Mw) of tremor bursts in northern Cascadia: implications for the "seismic efficiency" of episodic tremor and slip
AuthorKao, H; Wang, K; Dragert, H; Kao, J Y; Rogers, G
SourceGeophysical Research Letters vol. 37, L19306, 2010, 6 pages,
Alt SeriesEarth Sciences Sector, Contribution Series 20100169
Mediapaper; on-line; digital
File formatpdf
ProvinceWestern offshore region; British Columbia
NTS92A; 92B; 92E; 92F; 92K; 92L
Areanorthern Cascadia; Vancouver Islands; Victoria
Lat/Long WENS-128.0000 -122.0000 51.0000 48.0000
Subjectsgeophysics; seismic interpretations; seismic risk; seismic zones; seismicity; seismic surveys; seismic waves; s waves
Illustrationslocation maps; profiles; plots; histograms
ProgramTargeted Hazard Assessments in Western Canada, Public Safety Geoscience
AbstractWe develop a method to estimate the seismic moments of deep non-volcanic tremor bursts observed in northern Cascadia. For each tremor burst, the maximum amplitudes at individual stations within a time window ±5 s around the predicted arrivals of the S phase are measured and compared to the maximum S amplitudes measured from synthetic seismograms. The proposed method is thoroughly
calibrated using 464 local earthquakes and the results show excellent consistency between the reported ML and the estimated Mw. We apply the method to northern Cascadia tremors and infer that most bursts have Mw~1.0-1.7. The corresponding b value appears to be 1, consistent with that of ordinary earthquakes but over a narrower Mw range. Comparison of cumulative tremor Mw and the Mw estimated from the accompanying slow slip suggests that the "seismic efficiency" of the Episodic Tremor and Slip (ETS) is of the order of 0.1% or less.