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.

Class

Required string. NEHRP site class letter.

H (m)

Optional number in m. Profile depth to bedrock.

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

Site fundamental period Ts = 4H/Vs from a NEHRP class-typical profile depth and velocity. Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

T_s (s)

Returned number in s. Site fundamental 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.
• 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.

• 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.

• Site Class NEHRP From VS30 Lookup

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

• Site Kappa Zero By NEHRP Class Lookup

  Typical near-surface kappa ranges by NEHRP site class.