Induced Seismicity in Western Canada Linked to Tectonic Strain Rate: Implications for Regional Seismic Hazard

Abstract

A rapid increase of injection-induced earthquakes (IIE) is often linked to a higher level of seismic hazard. In this study, we compare the geodetically defined moment rate to seismicity distribution in western Canada where significant IIE are observed. The regional seismic pattern is dominated by IIE, both in number and moment, along a 150-km wide NW-SE band of moderate strain rate in the easternmost Cordillera and foothills. The observed rate of moment release from local earthquakes is much closer to the tectonic moment rate in the IIE-dominated areas. We conclude that, on a regional scale, tectonic strain rate is an important control on IIE. Injection in areas with moderate tectonic strain may temporarily increase the local seismic hazard, but widespread IIE over an extended period of time may deplete the available tectonic moment and could, under the right conditions, have a limited long-term effect of reducing regional seismic hazard.Plain Language Summary Fluids are commonly injected into oil and gas wells to shutter the reservoir formations of shale gas and tight oil and to increase production. However, not all injections cause induced earthquakes and some areas have more events than others. In this study, we examine the geological controls on where there is greatest susceptibility to induced earthquakes. In western Canada, we find that they are generally associated with the areas of moderate long-term geological/tectonic deformation rates, as mapped by the relative motion of high-resolution Global Navigation Satellite System stations. Most induced earthquakes are in a 150-km-wide band in the easternmost Canadian Cordillera and foothills. They are much less frequent farther to the east where the geological deformation rates are low. We conclude that the geological deformation rate is an important controlling factor for the occurrence of induced earthquakes. In some areas, the strain rate from induced earthquakes may temporarily exceed the natural geological strain rate. Widespread injections in areas with relatively high geological deformation rate may increase the regional seismic hazard in the short term. But if frequent occurrence of induced earthquakes persists over time, it could lead to a reduction of natural earthquake occurrence in the long term.

Machine Learning‐Based Analysis of Geological Susceptibility to Induced Seismicity in the Montney Formation, Canada

“…Based on our analysis, distance to the Cordilleran deformation front is one of the most important parameters affecting SAP. In part, this supports a model proposed by Kao et al (2018), who used sparse GPS data to show that the likelihood of induced seismicity in western Canada may be closely related to crustal strain rate. They identified a region in the foreland of the deformation front (Figure 3) that is characterized by both higher values of crustal strain rate and prevalence of induced seismicity.…”

Geodynamics

“…Although the selection of regions was based on the parameter b by the Kaltek method, which is more related to the nature of the earthquake, the constructed maps show that areas of increased risk of earthquakes correspond to the regions where the modern horizontal deformations are significant. Kao, et al, [2018] demonstrate correlations between crustal deformations and weak injection-induced earthquakes in Western Canada. To do this, the study area is divided into squares with sides of 20 km.…”

Statistical Modeling and Characterization of Induced Seismicity Within the Western Canada Sedimentary Basin

“…While the fundamental mechanisms for wastewater disposal-related seismicity are generally agreed upon, namely the diffusion of pore pressure promoting shear-failure along preexisting faults, the triggering processes of HF-induced seismicity remain less well understood. Fault reactivation may be attributable to several different sources, including hydraulic transmission between existing faults, new fractures and fluid injection wells (Galloway et al, 2018;Skoumal et al, 2018), fluid diffusion through semi-permeable rock causing pore pressure changes (Bao & Eaton, 2016), post-injection stress relaxation (Hajati et al, 2015), fluid-induced aseismic slip (Scuderi & Collettini, 2016;Scuderi et al, 2017;Bhattacharya & Viesca, 2019), fault maturity (Kozłowska et al, 2018;Brudzinski & Kozłowska, 2019), tectonic strain rates (Kao et al, 2018), and intra-cluster elastic stress redistribution and triggering of micro-seismicity (Stein, 1999;Sagiya et al, 2002;Maghsoudi et al, 2016Maghsoudi et al, , 2018. On the other hand, a recent study by Kettlety et al (2019) showed that elastic stress transfer may weakly promote failure initially during HF and later actually inhibit further slip.…”

“…The global rise in induced seismicity together with advancement in detection capability over the past decade has resulted in an abundance of earthquake data from which much new information is being gathered (Doglioni, 2018). Better understanding of tectonic strain rates, triggering mechanisms and geologic controls, updated hydrogeological models, and analyses of spatiotemporal clustering patterns and statistics have allowed for some improvements in the identification of induced activity and several adjustments to seismic hazard analysis (Llenos & Michael, 2013;Atkinson et al, 2016;Petersen et al, 2016;Zaliapin & Ben-Zion, 2016;Atkinson, 2017;Langevin et al, 2017;Schoenball & Ellsworth, 2017;Kao et al, 2018;Zhang et al, 2019). However, the wide-ranging and sometimes conflicting results attained across individual case studies (see Keranen & Weingarten, 2018) highlight the complex nature of induced seismic processes and illustrate the need for further investigation.…”