Guidance on Traffic-Light Thresholds and Magnitude Estimation for Induced Seismicity Management

Induced seismicity associated with hydraulic fracturing and fluid disposal has notably increased the seismic hazard in Alberta since the early 2010s. The Alberta Energy Regulator manages this hazard through area-specific subsurface orders for hydraulic fracturing and, more recently, through updated provisions in Directive 065 for fluid disposal operations, both of which rely on traffic-light protocols (TLPs) with earthquake magnitude thresholds. This Information Series provides guidance on two key aspects of implementing a TLP: the selection of magnitude thresholds and the consistent estimation of earthquake magnitudes. For threshold selection, we present the Magnitude Threshold for Acceptable Seismicity (MTAS) maps, derived from earthquake iso-nuisance and iso-damage maps for Alberta, as a minimum reference for establishing red-light thresholds, complemented by guidance on setting yellow-light thresholds. Two versions of the MTAS maps are provided, reflecting the different treatment of trailing seismicity for hydraulic fracturing and long-term injection activities. For magnitude estimation, we summarize the local magnitude relation of Yenier (2017), calibrated for the Western Canada Sedimentary Basin, and outline its practical implementation to promote consistent magnitude reporting across operators and monitoring networks.