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.

L (km)

Required number in km. Sub-fault rupture length.

v_r (km/s)

Required number in km/s. Rupture velocity.

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

First-order rupture-duration proxy for directivity pulse period: T_p ≈ L/v_r. Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

T_p (s)

Returned number in s. Narrowband pulse 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.
• L must be at least 0.
• v_r 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.

• Directivity Pulse Duration Near Source Calculator

  Forward-directivity timescale for a unilateral rupture, L·(1/v_r − 1/β), assuming the site lies along strike in the rupture direction.

• MS MB Explosion Discrimination Note Lookup

  First-order Ms/mb discrimination screen for event source type.

• Arias Intensity Duration Proxy Calculator

  Arias intensity proxy I_a ≈ (π/2g)·∫a² dt approximated by PGA² times effective duration.