Knowra Seismic magnitude scales Seismic magnitude scales Seismic magnitude scales assign earthquakes numerical values from seismic-wave measurements. Different scales quantify wave amplitude, seismic moment, or radiated energy, and can yield different values for the same earthquake.
Richter scale : A local magnitude scale that estimates earthquake size from the maximum amplitude recorded by a standard seismograph. It is the best-known early amplitude scale, calibrated for nearby earthquakes in southern California.
Seismology : The scientific study of earthquakes, seismic waves, and Earth's internal structure. Magnitude scales are one set of tools within this broader study.
Earthquake early warning : Systems that detect an earthquake's initial waves and issue alerts before stronger shaking reaches some locations. Rapid magnitude estimates help warning systems forecast the likely severity of shaking.
Earthquake intensity : A description of shaking and damage at a particular location, based on observed effects rather than source size. Unlike magnitude, intensity can vary from place to place for one earthquake.
Surface-wave magnitude : An earthquake magnitude scale based on the amplitude of surface waves, commonly measured at a period near 20 seconds. It extends amplitude-based measurement to distant earthquakes but can saturate for great events.
Seismic wave : An elastic disturbance that travels through Earth or along its surface, often generated by an earthquake. Magnitude methods extract measurements from these waves.
Earthquake catalog : A systematic record of earthquakes and their reported locations, times, depths, and magnitudes. Consistent magnitude choices make events easier to compare in catalogs.
Modified Mercalli intensity scale : A twelve-level scale describing earthquake effects on people, buildings, and the environment at a location. It measures experienced effects, not the earthquake's single source magnitude.
Body-wave magnitude : An earthquake magnitude scale based on the amplitude of seismic body waves, especially short-period compressional waves. It provides a distinct amplitude measure for waves that travel through Earth's interior.
Seismometer : An instrument that detects and records ground motion, including motion caused by seismic waves. Its recordings provide the amplitudes and wave periods used by several scales.
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