Tectonic, depth, and magnitude controls on global earthquake stress drop

Abstract

Abstract

Earthquake stress drop is a key parameter linking fault strength, rupture dynamics, and high-frequency ground motion, yet global observations exhibit variability spanning more than two orders of magnitude. This study reassesses the primary controls on stress-drop variability using a harmonized global database of 1748 earthquakes (Mw ≥ 5.5). Each event is classified by tectonic environment, focal depth, and faulting style, enabling a systematic evaluation of how these factors jointly influence stress drop. We find that intraplate earthquakes systematically exhibit higher stress drops than plate-boundary events across nearly all depth ranges. Depth exerts a strong control on stress-drop distributions: median values increase from the upper crust to the lithospheric mantle, and magnitude scaling becomes increasingly negative with depth. A multivariate regression incorporating Mw, depth, tectonic setting, and mechanism explains ∼4% of total variance, indicating substantial intrinsic variability but confirming that tectonic environment and depth contribute significant, though modest, systematic effects. Global kernel-smoothed maps reveal coherent regional patterns, including elevated stress drops within continental and oceanic intraplate domains and localized high-Δσ patches near subduction interfaces. K-means regionalization shows that ∼11% of the global variance in stress drop is attributable to large-scale tectonic domains. Faulting style produces weaker effects: reverse and strike-slip earthquakes show broadly similar distributions and magnitude scaling once depth and tectonic setting are accounted for. Collectively, these results demonstrate that tectonic environment and lithospheric depth are first-order controls on global stress-drop variability, providing new observational constraints on earthquake rupture physics and seismic hazard in intraplate regions.