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.

λ₁ (N·m)

Required number in N·m. First eigenvalue.

λ₂ (N·m)

Required number in N·m. Second eigenvalue.

λ₃ (N·m)

Required number in N·m. Third eigenvalue.

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

Scalar seismic moment from tensor eigenvalues: M̄ = √(Σλᵢ²/2). Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

M̄ (N·m)

Returned number in N·m. Scalar moment.

M_w

Returned number. Magnitude equivalent of the scalar moment.

• 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.

• Moment Tensor Double Couple Percent Decomposition Calculator

  Decompose ordered moment-tensor eigenvalues into isotropic and deviatoric amplitudes, then split the deviatoric share into double-couple and CLVD components; the three reported percentages sum to 100.

• Asperity Area Fraction Scaling Calculator

  Asperity area fraction A_a/A₀ as a power-law function of seismic moment, capped at the physical upper bound of one.

• Average Moment Rate From Moment Duration Calculator

  Average seismic moment release rate over a specified source duration: Ṁ₀ = M₀/T.