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.

Vs (m/s)

Required number in m/s. Layer shear velocity.

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

Soft-soil resonant frequency f₀ = Vs/(4H) for a layer over rigid bedrock. Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

f₀ (Hz)

Returned number in Hz. Fundamental resonant frequency.

T₀ (s)

Returned number in s. Resonant period.

• 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.
• Vs 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.

• Quarter Wave Layer Higher Mode Harmonics Calculator

  Quarter-wavelength harmonics f_n = (2n−1)·Vs/(4H) for a layer over stiff half-space.

• Average Radiation Factor Boore Boatwright Lookup

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

• Brune Displacement Spectrum Peak Frequency Note

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