Induced or Natural? Assessing the North Peace River Seismic Cluster Using Nodal Array Data, Regional Catalog, and Evidence-Based Scoring Tool Inputs

Seismic nodal arrays are increasingly used in local-scale seismic studies for their rapid, cost-effective deployment and ability to provide high-resolution event locations that enhance understanding of seismic clusters. In this study, we use results from nodal array processing such as event locations, magnitudes, and source mechanisms together with regional earthquake catalogs and industrial operations data to evaluate the origin of seismicity in the area north of the town of Peace River, northwestern Alberta.

Over a three-month deployment, the nodal array detected 340 events, with the largest event having a local magnitude of 2.83. Among these, 29 events had local magnitudes greater than or equal to 1, and 13 of these events were not detected by the regional seismic array. Despite limited spatial coverage with only seven nodes, event locations show good agreement with those recorded by the regional array. The primary depth distribution of the nodal array events is between 4 and 6 km below the ground surface, suggesting that the events occurred in the Precambrian basement. Additionally, the nodal array identified a small seismic cluster within 15 km of disposal wells, previously undetected by the regional array. This highlights the improved local resolution of event locations provided by the nodal array, which is critical for assessing induced seismicity.

To further evaluate the North Peace River seismic cluster, we used nodal array data together with regional earthquake catalogs and industrial operations information in the application of the Foulger et al. (2023) questionnaire, which emphasizes spatio-temporal correlations with industrial activity. We also performed correlation analysis between annual seismicity rates from the regional catalog and injection volumes, revealing a strong temporal association that persists across multi-year lags. Questionnaire results indicate 61% of points support an induced origin, 28% are equivocal, 11% insufficient, and 0% natural. These findings demonstrate that nodal arrays significantly enhance detection and interpretation of local seismicity, providing valuable input for identifying and characterizing induced seismicity.