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.

h (m)

Required number in m. Layer thickness.

V₁ (m/s)

Required number in m/s. Upper layer velocity.

V₂ (m/s)

Required number in m/s. Half-space velocity.

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

Crossover distance where direct and head waves arrive together: x_c = 2h·√((V₂+V₁)/(V₂−V₁)). Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

x_c (m)

Returned number in m. Crossover distance.

θ_c (°)

Returned number in °. Critical incidence angle.

• 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.
• h must be at least 0.
• V₁ must be at least 0.
• V₂ 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.

• S-P Interval Hypocentral Distance Calculator

  Hypocentral distance from the S-minus-P interval in a single-layer model: d = Δt / (1/V_s − 1/V_p).

• AGC Gain Step Artifact Flagger

  Flag windows where automatic-gain-control steps coincide with event energy.

• Average Radiation Factor Boore Boatwright Lookup

  Boore-Boatwright style average radiation factors for P and S waves over the focal sphere.