What is recorded here?
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. To compare earthquakes, a reading at one station must be corrected for the distance and the instrument. Richter combines an empirical distance curve with logarithmic amplitude ratios so multiple stations can assign an approximately consistent event size. The scale was designed to organize a huge range of recorded shocks, including events with few reported surface effects. Its usefulness depends on calibration and observational coverage; site intensity and damage remain different quantities.
Source-linked catalogue note. A detailed explanatory guide has not yet been prepared for this entry.
Scientific scope
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.
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People and systems
Charles F. Richter
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English catalogue narrative
Richter: a local instrumental earthquake magnitude scale
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.
To compare earthquakes, a reading at one station must be corrected for the distance and the instrument. Richter combines an empirical distance curve with logarithmic amplitude ratios so multiple stations can assign an approximately consistent event size. The scale was designed to organize a huge range of recorded shocks, including events with few reported surface effects. Its usefulness depends on calibration and observational coverage; site intensity and damage remain different quantities.
Scientific scope
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.
People and systems
Charles F. Richter