Strain Accumulation and Release Rate in Canada: Implications for Long‐Term Crustal Deformation and Earthquake Hazards.

To advance the understanding of crustal deformation and earthquake hazards in Canada, we analyze seismic and geodetic data sets and robustly estimate the crust strain accumulation and release rate by earthquakes. We find that less than 20% of the accumulated strain is released by earthquakes across the study area providing evidence for large‐scale aseismic deformation. We attribute this to glacial isostatic adjustment (GIA) in eastern Canada, where predictions from the GIA model account for most of the observed discrepancy between the seismic and the geodetic moment rates. In western Canada, only a small percentage (<20%) of the discrepancy can be attributed to GIA‐related deformation. We suspect that this may reflect the inaccuracy of the GIA model to account for heterogeneity in Earth structure or indicate that the present‐day effect of GIA in western Canada is limited due to the fast response of the upper mantle to the deglaciation of the Cordillera Ice Sheet. At locations of previously identified seismic source zones, we speculate that the unreleased strain is been stored cumulatively in the crust and will be released as earthquakes in the future. The Gutenberg‐Richter model predicts, however, that the recurrence interval can vary significantly in Canada, ranging from decades near plate boundary zones in the west to thousands of years in the stable continental interior. Our attempt to quantify the GIA‐induced deformation provides the necessary first step for the integration of geodetic strain rates in seismic hazard analysis in Canada. Plain Language Summary: We took advantage of the increasing density of Global Navigation Satellite System and seismic stations across Canada to perform a detailed investigation of the strain buildup and release rate by earthquakes. Our results indicate that strain release rates by earthquakes are slower than the strain accumulation rates except at locations where earthquakes are generated due to tectonic and/or man‐made activities. We compare our results to the estimated rate of strain accumulation due to postglacial rebound and found that the postglacial rebound model can satisfactorily explain our observation in eastern Canada but not in western Canada. Consequently, we infer that the effect of the postglacial rebound in western Canada may be short lived or the model used is less accurate. We investigate the possibility that strain is cumulatively stored in the crust and can be released by future earthquakes. Our results reveal that the recurrence interval of a major earthquake (magnitude ≥ 6) can vary significantly in Canada, ranging from decades near plate boundary zones in the west to thousands of years in the stable continental interior. Our study demonstrates the advantage of jointly analyzing seismic and geodetic data sets to obtain a more complete picture of crustal deformation and potential seismic hazard. Key Points: Analysis of seismic and geodetic data sets across Canada reveals that only 20% or less of the accumulated strain is released by earthquakesGlacial isostatic adjustment model can account for most of the discrepancy between the seismic and geodetic moment rates in eastern Canada, but not in western CanadaThe recurrence time of large earthquakes in Canada varies from decades near the plate boundary to millenniums in the plate interior [ABSTRACT FROM AUTHOR]