Earthquake Populations From Stochastic Stress Fields
Journal
Journal of Geophysical Research: Solid Earth
Journal Volume
131
Journal Issue
7
ISSN
2169-9313
2169-9356
Date Issued
2026-07
Author(s)
Abstract
Earthquakes occur in populations with few large events and many small ones, yet many earthquake rupture models employ a smooth stress field and other conditions that prohibit the co-occurrence of large earthquakes and smaller foreshocks and aftershocks. We describe populations of earthquakes that propagate and arrest within a stochastic stress field Δτpot(x) using a 1D fracture mechanics framework. Δτpot(x) is characterized by its mean (meanΔτ), standard deviation (stdevΔτ), and scaling exponent (mΔτ), which describes how Δτpot(x) changes as a function of wavelength. Δτpot(x) is related to the strain energy that fuels earthquakes, and it embodies the heterogeneous stresses that develop in fault zones with multi-scale geometrical complexity. Realistic populations of earthquakes, with more small ones than large ones, are produced by highly variable fields with stdevΔτ (8–80 MPa) that far exceeds meanΔτ, resulting in significant sections with highly negative Δτpot(x). Earthquake populations produced by such variable stress fields exhibit b-values that decrease with increasing meanΔτ and stress drops that are primarily correlated with stdevΔτ, are independent of magnitude, and may be limited by the strength of rocks at seismogenic depths. Our preferred models suggest 0 ≤ mΔτ ≤ 0.25 (mΔτ = 1.5 is self-similar, 1.0 is Brownian, 0 is white noise), consistent with expectations based on multiscale roughness measured on exhumed faults. This suggests that Δτpot(x) must be highly variable and highly negative, even at short wavelengths, a property that strongly influences the earthquake energy budget but is absent from state-of-the-art dynamic rupture models and unresolvable with kinematic finite-fault inversions.
Subjects
b-value
earthquake mechanics
fault architecture
fault roughness
heterogeneity
self-affine
Publisher
American Geophysical Union (AGU)
Type
journal article