Use this geological calculation for a transparent first-pass interpretation of measured rock, soil, fluid, well, stratigraphic, isotopic, geophysical, or seismic data under an explicitly selected model.

Event latitude

Event latitude in decimal degrees.

Event longitude

Event longitude in decimal degrees.

Station latitude

Station latitude in decimal degrees.

Station longitude

Station longitude in decimal degrees.

Great-circle epicentral distance from event to station via the haversine formula on a spherical Earth of mean radius 6371 km. The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.^[1]

Central angle

Great-circle central angle in degrees.

Distance

Epicentral distance along the surface in kilometers.

• Seismic magnitudes, moments, travel times, velocities, resolution, and energy depend on instrument correction, Earth model, phase picking, geometry, attenuation, radiation pattern, bandwidth, and calibration range. Magnitude scales are not universally interchangeable.
• Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Compare independent measurements and models, retain units and analytical metadata, propagate uncertainty, and validate interpretations against logs, cores, maps, laboratory data, or field observations.

• Richter Magnitude From Amplitude Calculator

  Original Richter (1935) local magnitude ML = log10(A / A0), comparing maximum Wood-Anderson trace amplitude in millimeters with the zero-magnitude reference amplitude at the same epicentral distance (0.001 mm at 100 km by definition).

• Earth Pressure At Rest Calculator

  At-rest lateral earth pressure for a normally consolidated soil via Jaky K0 = 1 - sin(phi): horizontal effective stress sigma_h' = K0 * sigma_v'. Stress in kPa, angle in degrees.

• Mohr Circle Center Calculator

  Center of the Mohr circle for two principal stresses: sigma_center = (sigma_1 + sigma_3) / 2 on the normal-stress axis.