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.

m (1/Hz)

Required number in 1/Hz. Slope of ln(A₁/A₂) versus frequency.

Δt (s)

Required number in s. Lapse-time difference between stations.

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

Two-station coda Q from the log spectral-ratio slope: ln(A₁/A₂) = −π f Δt / Q. Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

Q_c

Returned number. Estimated coda quality factor.

Valid?

Returned boolean. Whether the slope has the attenuation sign.

• 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.
• Δt 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.

• Wadati Origin Time Single Station Formula Calculator

  Origin-time estimate from one station using the Wadati ratio: t₀ = (R·t_p − t_s)/(R − 1).

• Coda Duration Magnitude Nuttli Formula Calculator

  Nuttli-style coda-duration magnitude M_d = a + b·log₁₀(τ) + c·Δ with regional coefficients.

• Damping Response Spectrum Heuristic Scaling

  Heuristic spectral scaling from 5% to another damping ratio: F = (0.05/ζ)^0.25.