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.

T (s)

Required number in s. Period.

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

Approximate NLNM/NHNM acceleration power (dB relative to 1 (m/s²)²/Hz) at a period, log-linearly interpolated from a reduced set of Peterson (1993) anchors. Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

NLNM (dB)

Returned number in dB. New low-noise model power.

NHNM (dB)

Returned number in dB. New high-noise model power.

• 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.
• T 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.

• Uniform Hazard Spectrum Interpolation Calculator

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• 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.