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.

d (km)

Required number in km. Typical station spacing.

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

Illustrative magnitude-of-completeness screening relation M_min ≈ 1.5 + log₁₀(r/km) using a detection radius of 1.5 times station spacing; it is not a calibrated network threshold. Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

r (km)

Returned number in km. Assumed detection radius (= 1.5×spacing).

M_min

Returned number. Completeness magnitude at that radius.

• 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.
• d 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.

• 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.

• Basin Edge Surface Waves Checker

  Screen whether the bedrock-to-basin shear-wave velocity contrast reaches an illustrative 2:1 threshold associated with stronger basin-edge effects; geometry is not modeled.

• Characteristic Earthquake Magnitude Window Lookup

  Estimate characteristic magnitude from a fault length using the Wells & Coppersmith strike-slip relation.