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.

V_i

Required list. Layer velocities top-down.

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

Flag layers that cannot produce a critically refracted first arrival because their velocity does not exceed every overlying layer velocity. Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

Hidden

Returned list. Zero-based indices of potential low-velocity or equal-velocity hidden layers.

Trustworthy

Returned boolean. Whether velocity increases strictly with depth; this is necessary, but not sufficient, for every interface to be resolved.

• 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.

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