Very low frequency earthquakes spatiotemporally asynchronous with strong tremor during the 2014 episodic tremor and slip event in Cascadia

We find very low frequency earthquakes (VLFEs) in Cascadia during the 2014 episodic tremor and slip event under Washington and Vancouver Island using a grid search centroid moment tensor inversion method. The very low frequency earthquakes occur when and where there is no strong tremor detected, contrasting with previous findings where tremor and very low frequency earthquakes have a clear spatiotemporal relationship. This challenges our current understanding of the dynamic relationship between the different types of slow earthquakes and their relationship to slow slip. We interpret these findings to suggest that VLFEs and tremor may have their own seismic cycles, resulting from asperities of different sizes or characteristics that respond pseudo-independently to stress loading. We propose that very low frequency earthquakes and tremor are subject to asynchronous seismic cycles.