Fluid Injection And Seismic Activity In The Northern Montney Play, British Columbia, Canada, With Special Reference To The 17 August 2015 M-W 4.6 Induced Earthquake

In this article, we analyzed the recent seismic activity in the northern Montney Play of British Columbia in 2015 and its connection with fluid injection (hydraulic fracturing and long-term injection of gas and wastewater disposal) in the region. The earthquake sequence used in this study includes 676 events from 3 October 2014 to 31 December 2015 from the Progress Energy earthquake catalog with moment magnitude as small as 1. Spatial and temporal correlation of seismic activity with the fluid injection in the region revealed that these events are better correlated with hydraulic fracturing (correlation coefficient of similar to 0.17 at confidence level close to 99.7%, with a lag time between 0 and 2 days) than other types of injection. Using the double-difference relocation technique, we obtained depth constraints for some of the events for which supplementary, industry-provided waveforms were available. The depths of these events range from 0.5 to 2.5 km and are mostly constrained above the target zone where hydraulic fracturing was taking place. The best-fit moment tensor solution for the event on 17 August 2015 gives a moment magnitude of 4.6 and a predominantly thrust mechanism in the northwest-southeast direction with a shallow focal depth of 4 km. This is consistent with that obtained through double-difference relocation for this event (1.3 km), given the depth uncertainty of the moment tensor inversion.