Mining-Related b-Value Anomalies in the Upper Crust: A High-Resolution Ring Analysis Across Chilean Mining Districts

Mining districts in Chile are located within one of the most seismically active tectonic environments on Earth, which makes it challenging to distinguish between natural crustal seismicity and seismicity potentially influenced by mining. A key open question is whether large-scale mining operations produce a measurable and spatially coherent statistical signature in the surrounding shallow crust. In this study, we evaluate this hypothesis using the Gutenberg–Richter b-value as a quantitative proxy for local stress conditions and the degree of rock mass damage and fracturing. We focus on the seismic environment surrounding major mining districts in Chile, restricting the analysis to shallow crustal events with depths shallower than 10 km. This depth filter aims to isolate the seismic response of the upper crust that is most likely to be affected by mining-related stress perturbations, while reducing the contribution of deeper subduction-driven tectonic seismicity. To resolve spatial variations at kilometer scale, we implement a high-resolution concentric-ring analysis centered on each mining district, using 1 km radial bins extending outward from the extraction centers. To ensure statistical robustness and comparability across sites, the magnitude of completeness (Mc) is estimated dynamically using the maximum curvature method, yielding reference values close to ML ≈ 1.87 for the analyzed catalog. The Gutenberg–Richter b-value is then computed using the Aki–Utsu maximum-likelihood estimator, providing a rigorous and stable framework for inter-site comparisons under contrasting geomechanical and operational settings. The analysis reveals clear and systematic differences depending on the mining method. Underground mining environments show a pronounced increase in b-value (b > 1.5) within the first ~5 km, consistent with elevated rates of microseismicity and enhanced brittle damage associated with caving-related processes. In contrast, open-pit operations exhibit a comparatively stable b-value pattern with lower spatial dispersion. In both settings, b-values progressively converge toward the regional tectonic reference level (b ≈ 1.0) with increasing distance from the extraction centers, suggesting a characteristic radius of direct mining influence on the order of ~15–20 km. These preliminary results show that kilometer-scale mapping of the Gutenberg–Richter b-value provides a sensitive and interpretable metric to quantify the spatial footprint of mining-related seismic perturbations in the shallow crust. The observed b-value gradients offer a practical tool for regional-scale geomechanical monitoring, supporting the discrimination between background tectonic seismicity and elastic stress changes induced by excavation and/or large-volume rock mass caving in Chilean mining districts.