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.

dᵢ

Required list. Layer thicknesses (m), top-down.

Vsᵢ

Required list. Layer shear velocities (m/s), top-down.

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

Time-averaged shear velocity over the top 30 m: VS30 = 30 / Σ(dᵢ/Vsᵢ). Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

VS30 (m/s)

Returned number in m/s. Time-averaged shear velocity to 30 m.

Depth (m)

Returned number in m. Profile depth used for the average (truncated at 30 m).

• 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.

• Site Class NEHRP From VS30 Lookup

  NEHRP site class (A–E) from time-averaged shear velocity.

• Source Rise Time Dislocation Calculator

  Characteristic source timescale estimated as fault width divided by shear-wave velocity; this is a dimensional proxy, not a fitted rupture rise-time model.

• 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.