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.

r (km)

Required number in km. Distance.

r₀ (km)

Optional number in km. Reference distance.

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

Surface waves in a half-space spread geometrically as 1/√r. Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

√(r₀/r)

Returned number. Amplitude spreading factor.

• 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.
• r 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.

• 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.

• Dip-Slip Seismic Moment and Average Dislocation Estimate

  Seismic moment and average dislocation estimate for a dip-slip rupture: geodetic moment M₀ = μ·A·ū plus a heuristic vertical offset scale; this tool does NOT solve the Okada (1992) elastic half-space displacement field.

• Strike-Slip Seismic Moment and Average Dislocation Estimate

  Seismic moment and average dislocation estimate for a strike-slip rupture: geodetic moment M₀ = μ·A·ū and a half-slip (ū/2) offset scale; this heuristic does NOT compute the Okada (1992) elastic half-space spatial displacement field.