Probing the effects of a transient stress on the timing of an earthquake occurrence is necessary for understanding the remote interaction of large-magnitude events. Global catalog data containing 35 years of M ≥ 5.5 earthquakes allow us to explore for periods of enhanced or suppressed seismic activity. We consider 113 M ≥ 7.5 main shocks between 1977 and 2012 and focus on seismic activity on time scales from seconds to days following these main shocks. We search for evidence of dynamic triggering of large-magnitude events similar to the previously observed global increase during the first few days following the 2012 M8.6 Indian Ocean main shock. We restrict the analysis to regions of elevated strain during the passage of surface waves. Using a threshold of 0.1 microstrain (∼3 kPa) and a temporal window of ±1 year, we stack daily seismicity rate curves using the exclusion-zone declustered M ≥ 5.5 catalog events in order to resolve deviations from the background rate. Our results do not indicate a significant change in activity for at least 10 days when considering the collective set of 113 main shocks and subsets at M8.0 and M8.5 thresholds. The results also do not indicate immediate triggering of M ≥ 5.5 events. We do find two instances of increased seismicity in the elevated strain region within 10 days. These increases are subsequent to two main shocks, the 1977 M8.3 and 2012 M8.6, both located in the Indian Ocean. We conclude that a global change in M ≥ 5.5 earthquake rates following a transient stress from distant earthquakes is a rare occurrence.

The 3 September 2016 Mw 5.8 Pawnee earthquake in northern Oklahoma is the largest earthquake ever recorded in Oklahoma. The coseismic deformation was measured with both Interferometric Synthetic Aperture Radar and Global Positioning System (GPS), with measureable signals of order 1 cm and 1 mm, respectively. We derive a coseismic slip model from Sentinel-1A and Radarsat 2 interferograms and GPS static offsets, dominated by distributed left-lateral strike slip on a primary west-northwest-east-southeast-trending subvertical plane, whereas strike slip is concentrated near the hypocenter (5.6 km depth), with maximum slip of ∼1 m located slightly east and down-dip of the hypocenter. Based on systematic misfits of observed interferogram line-of-sight (LoS) displacements, with LoS based on shear-dislocation models, a few decimeters of fault-zone collapse are inferred in the hypocentral region where coseismic slip was the largest. This may represent the postseismic migration of large volumes of fluid away from the high-slip areas, made possible by the creation of a temporary high-permeability damage zone around the fault.