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.

γ (%)

Required number in %. Cyclic shear strain amplitude.

Soil

Required string. Generic soil category.

The cited overview of Seismic site effects supplies background for the terminology and domain context used by this tool.^[1]

Shear modulus reduction (degradation) factor for soil at a given cyclic shear strain. Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

G/G_max

Returned number. Normalized shear modulus.

Regime

Returned string. Linear / nonlinear / failing regime.

• 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.
• γ must be at least 0.
• 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.

• Air Coupled Rayleigh Wave Speed Calculator

  Rayleigh wave speed from shear velocity (≈0.92·β for ν = 0.25) compared with the speed of sound in air.

• Average Radiation Factor Boore Boatwright Lookup

  Boore-Boatwright style average radiation factors for P and S waves over the focal sphere.

• 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.