Forecasting of Induced Seismicity Rates from Hydraulic Fracturing Activities Using Physics-Based Models for Probabilistic Seismic Hazard Analysis: A Case Study

One of the major challenges in seismic hazard analysis for induced seismicity is the forecasting of future seismicity rates, which are described by the Gutenberg–Richter parameters (a and b-values from the earthquake magnitude frequency distributions). In this study, we implement two methodologies in order to determine the Gutenberg–Richter parameters related to future induced seismicity: the Seismogenic Index and the Hydromechanical Nucleation model. We apply both methods in one recent case of induced seismicity: the Horn River Basin, Northeast B.C., Canada. We perform two tests to compare the predictions of both models with the observed seismicity. First, we compare the predicted number of earthquakes exceeding a certain magnitude per month with the observed number of earthquakes. In this test, both methods predict earthquake rates similar to the observed induced seismicity in the Horn River Basin. Second, we evaluate how appropriate are the predictions for specific magnitude ranges (given by forecasted Gutenberg–Richter parameters). In this case, both models make inaccurate predictions for specific magnitude ranges (annual magnitude frequency distributions), resulting in an under- or overestimation of the hazard but often with contradicting forecasts, despite using shared observations. The predictions under- and overestimate the hazard at different time points, due to the complexity in the evolution of the seismicity, and the assumption of constant b-values. As a result, these incorrect forecasts for future magnitude-frequency distributions lead to biased seismic hazard and ground motion predictions. More research effort is required in order to forecast more accurate Gutenberg–Richter parameters, particularly changes in the b-value, as observed in the Horn River Basin induced seismicity case.