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.

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

Båth's law: the largest aftershock sits about 1.2 magnitude units below its mainshock. Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

M_as

Returned number. Expected largest aftershock.

ΔM

Returned number. Båth gap used.

Note

Returned string. Empirical status.

• 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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  Classify a smaller event as probable foreshock based on its proximity in time and distance to a larger successor.