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

Required number. Mainshock magnitude.

Mc

Optional number. Completeness magnitude of the count.

α

Optional number. Productivity exponent.

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

Relative ETAS-style aftershock productivity 10^[α(M−Mc)]. It omits the fitted productivity constant and Omori time integral, so it is a relative factor rather than an expected event count. Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

λ₀

Returned number. Dimensionless productivity factor before applying a fitted normalization and time integral.

×10^α

Returned number. Productivity multiplier for a one-unit magnitude increase.

• 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.

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