Determining the spatio-temporal patterns of intraplate earthquakes of the Western Quebec Seismic Zone using clustering analysis

The Western Quebec Seismic Zone (WQSZ) is an intraplate region of Canada that experiences an unusual amount of earthquake activity far from plate boundaries. Over the past 40 years, more than 2000 earthquakes have been recorded in the WQSZ. Although the majority of earthquakes occur at relatively low magnitudes (between M 2-3), Canada’s national capital, Ottawa, and its second-largest city, Montréal, are both located within the WQSZ. As a result of their political and economic importance, the Canadian Government implemented an Earthquake Early Warning system to the region in late 2025.

Previous studies have primarily focused on potential faulting mechanisms and/or large earthquakes in the region (M > 5). However, the WQSZ is relatively understudied, with limited modern data science techniques applied to the seismic database. Given the wide surface area covered by the region and the regularity of events (i.e. an earthquake every 6.5 days), there is an urgent need to better understand the spatial and temporal patterns of seismicity across the WQSZ to further inform the hazards on a more local scale.

Clustering analysis is used to help group data into spatial patterns where the relationship is previously unknown. In this study, we apply an unsupervised machine learning clustering algorithm, Density-Based Spatial Clustering of Applications with Noise (DBSCAN), to analyze seismicity in the WQSZ and to delineate distinct spatial clusters. However, the output of the clustering analysis through DBSCAN is dependent on the choice of values for key parameters. To address this, a wide range of parameter values are tested to create a broad suite of cluster patterns and a statistical framework is developed to help identify the most robust patterns that best represent the geological and geophysical context for the region.

Our framework combines DBSCAN patterns with temporal, statistical and geological analysis to create a new high-resolution spatio-temporal characterization of seismicity in the WQSZ. These findings not only improve the understanding of localized seismic risk in Western Québec but also provide an application of cluster analysis to real-world logistical issues of seismic hazard analysis, including identifying areas of highest risk for earthquake preparedness and emergency planning in the region.