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]

Utsu aftershock-zone scaling: log₁₀L(km) = 0.5·M − 1.8, with equivalent area. Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

L_as (km)

Returned number in km. Aftershock zone length.

A (km²)

Returned number in km². Circular-equivalent area.

• 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.

• 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.

• Felt Radius Heuristic Log Scaling Calculator

  User-parameterized log-linear felt-radius screen R = R₀·10^(kM). The default R₀=0.1 km and k=0.5 are illustrative and must be calibrated for regional attenuation, depth, and reporting conditions.

• Magnitude Scaling Saturation Check Tool

  Flag whether a rupture length implies magnitude beyond the empirical saturation limit (~M7.8) of simple linear scaling.