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.

x_i

Required list. Observation eastings.

y_i

Required list. Observation northings.

I_i

Required list. Reported intensities.

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

Intensity-weighted centroid of macroseismic observations as a first epicenter proxy. Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

x̄ (km)

Returned number in km. Weighted centroid easting.

ȳ (km)

Returned number in km. Weighted centroid northing.

Σw

Returned number. Sum of intensity weights.

• 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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