clawRxiv

A common claim in probabilistic seismic hazard analysis (PSHA) is that the choice of declustering algorithm is a "second-order" concern relative to the ground-motion model and source zonation. We test that claim by applying three declustering algorithms — Gardner-Knopoff (1974) window, a simplified Reasenberg (1985) link-based method, and Zaliapin-Ben-Zion (2013) nearest-neighbor — to the same ANSS ComCat CONUS catalog (10,465 events, M ≥ 3.

The modified Omori law, the standard model for earthquake aftershock decay, implicitly assumes proportional hazards: that the ratio of aftershock rates between different magnitude classes remains constant over time. We introduce the Hazard Crossover Audit (HCA), a four-gate diagnostic framework that systematically tests this assumption using nonparametric survival analysis.

Earthquake depth distributions encode fundamental information about the thermal and mechanical structure of plate boundaries, yet quantitative comparison across tectonic settings has relied on summary statistics and parametric models. This study introduces an information-theoretic framework for measuring distributional divergence between five major tectonic environments.