Use this seismology calculation to reproduce a stated convention, screen observations, or compare scenarios whose units, coordinate conventions, catalog selection, and model assumptions are known.

Δτ (bar)

Required number in bar. Shear stress change in slip direction.

Δσn (bar)

Required number in bar. Normal stress change (positive = unclamping).

μ′

Optional number. Effective friction coefficient.

The cited overview of Fault (geology) supplies background for the terminology and domain context used by this tool.^[1]

Coulomb failure stress change on a receiver plane: ΔCFF = Δτ + μ′·Δσn (tension positive convention). Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

ΔCFF (bar)

Returned number in bar. Positive values encourage failure.

Verdict

Returned string. Common threshold interpretation.

• Earth structure, source geometry, path effects, site response, instrument response, catalog completeness, uncertainty, and the fitted range can dominate the accuracy of simplified seismic calculations.
• Use finite inputs in the displayed units, preserve source measurements and assumptions, and independently verify consequential decisions.

For analysis or hazard decisions, retain uncertainty and provenance and compare the result with waveform processing, calibrated regional models, and guidance from qualified seismologists or the responsible agency.

• Reservoir Induced Stress Change Bar Calculator

  First-order Coulomb stress perturbation under a reservoir load: Δσ ≈ ρ·g·h.

• Apparent Stress Energy Ratio Calculator

  Apparent stress σ_app = μ · Es / M₀ in megapascals.

• Corner Frequency Stress Drop Consistency Checker

  Invert the Brune relation fc = 0.49·β·(Δσ/M₀)^(1/3) for stress drop Δσ = M₀·(fc/(0.49·β))³ given the moment and compare with a claimed Δσ; no rigidity term is needed because Δσ/M₀ replaces it.