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 class A-E.

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

Typical near-surface kappa ranges by NEHRP site class. Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

κ₀ lo (s)

Returned number in s. Low bound of typical kappa.

κ₀ hi (s)

Returned number in s. High bound of typical kappa.

κ₀ mid (s)

Returned number in s. Midpoint value.

• 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.

• NEHRP Fundamental Period Site Lookup

  Site fundamental period Ts = 4H/Vs from a NEHRP class-typical profile depth and velocity.

• Site Class NEHRP From VS30 Lookup

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

• Amplification Borcherdt Factor Lookup

  Borcherdt-style short-period amplification factor from NEHRP class.