Precursory Accelerating Moment Release in the Northeastern United States and Southeastern Canada

The research presented here is part of a larger investigation of the physical processes underlying accelerating moment release (AMR). Numerous studies have documented AMR preceding large plate boundary earthquakes. There is little agreement, though, on the physical mechanism that causes precursory AMR. It may be possible to narrow the range of reasonable models by exploring the existence of AMR in intraplate settings. Analyzing intraplate AMR has proven challenging because of the lower seismicity rates and typically poor network coverage. Our study examines the northeastern U.S. and southeastern Canada, where the quality of the catalog data available permits a meaningful analysis of seismicity rate changes preceding moderate to large events. We find that approximately one third of the earthquakes of magnitude 5.0 or greater are preceded by statistically significant AMR sequences. The development of AMR, as well as the spatial and temporal scale of the precursory sequences, does not appear to be correlated with the magnitudes or faulting styles of the mainshocks.