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.

V₁ (m/s)

Required number in m/s. Velocity above the interface.

V₂ (m/s)

Required number in m/s. Velocity below the interface.

i (°)

Required number in °. Ray incidence angle to test.

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

Critical angle for a reflecting interface from velocity contrast, with post-critical guidance. Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

i_c (°)

Returned number in °. Critical angle.

Post-crit?

Returned boolean. Whether the tested ray is beyond critical.

• 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.
• V₁ must be at least 0.
• V₂ must be at least 0.
• i must be at least 0.
• i must be no greater than 90.
• 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.

• Air Coupled Rayleigh Wave Speed Calculator

  Rayleigh wave speed from shear velocity (≈0.92·β for ν = 0.25) compared with the speed of sound in air.

• 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.

• Brune Displacement Spectrum Peak Frequency Note

  For the Brune model, displacement amplitude peaks exactly at the corner frequency.