AWhat changed
Richter constructs an empirical local earthquake magnitude scale from the logarithm of standardized instrumental amplitudes corrected for epicentral distance, separating event size from intensity at a particular site.
Scientific scope
Richter constructs an empirical local earthquake magnitude scale from the logarithm of standardized instrumental amplitudes corrected for epicentral distance, separating event size from intensity at a particular site. The target is the 1935 Southern California instrumental scale, not all modern magnitude scales or an exact measurement of released energy. It uses a standard short-period torsion seismometer, a 100-km reference distance and a 1-micron reference trace amplitude. Each magnitude unit multiplies that calibrated amplitude by 10; magnitude 0 is the reference event, not no earthquake. The distance correction is empirical, based initially on January 1932 shocks. Source mechanism, depth, azimuth, local ground and instrument response cause deviations; ordinary reports are rounded to half units, with finer estimates for selected events. The original calls its precision crude. Calibration below 25 km is unsupported, while the inverse-cube extrapolation beyond the tabulated distances requires more evidence. Large traces can be off-scale or underexposed, forcing uncertain comparisons with aftershocks. Its rough energy estimates are conditional and not a modern universal energy conversion. Detection range, clustering and geographic selection affect frequency tables. Historical damage/perceptibility descriptions are not current forecasts or safety advice. Original seismograms/calibrations and exact table glyphs were not independently reconstructed.
Evidence
Source-linked, scoped account of the original work. The published scope states the scientific assumptions and remaining verification limits. WRS has not independently certified the full proof, experimental result or system benchmark.
Contributors
- Charles F. Richter · SCIENCE: Original source-listed scientific author of this scoped work; byline does not determine effort fractions.
Provisional WRS assessment, edition 2026-10-16.1. Independent expert calibration is pending. This grade does not certify correctness or assign ownership.
Full scientific record · Browse contribution grades · Request a correction