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.

N

Optional integer. Number of modes.

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

Quarter-wavelength harmonics f_n = (2n−1)·Vs/(4H) for a layer over stiff half-space. Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

f_n (Hz)

Returned list in Hz. Odd-quarter-wave harmonic frequencies.

• 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.
• N must be at least 1.
• N must be no greater than 10.
• 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.

• Resonance Quarter Wavelength Soft Soil Calculator

  Soft-soil resonant frequency f₀ = Vs/(4H) for a layer over rigid bedrock.

• Love Wave Dispersion Period Speed Lookup

  Illustrative fundamental-mode Love-wave phase-speed bands for a generic continental crust. Real dispersion must be calculated from a site-specific velocity model.

• 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.