Seismic intensity scales

Seismic intensity scales rate the shaking and effects of an earthquake at particular locations. They use observations such as how people felt the shaking and how buildings or the environment were affected.

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Earthquake intensity: A rating of earthquake shaking and its effects at a particular location. The scales are systems for assigning and comparing these local ratings.
Modified Mercalli intensity scale: A twelve-level scale rating earthquake intensity from observed effects on people, buildings, and the environment. It is a widely used example of an effects-based intensity scale.
Rossi–Forel scale: A ten-degree earthquake intensity scale introduced in the late nineteenth century by Michele Stefano de Rossi and François-Alphonse Forel. It was an early systematic scale for describing observed earthquake effects.
ShakeMap: A system that rapidly maps earthquake ground shaking using instrument records, models, and observations. It presents spatial shaking estimates in a form comparable to intensity maps.
Moment magnitude scale: A logarithmic scale estimating earthquake size from seismic moment, which reflects fault area, slip, and rock rigidity. It estimates source size rather than the effects at a particular location.
Earthquake magnitude: A measure of the size of an earthquake based on seismic-wave records or fault rupture. Magnitude describes the earthquake’s size, while intensity varies from place to place.
European Macroseismic Scale 1998: A twelve-degree scale for classifying earthquake intensity from observed effects, with detailed building vulnerability classes. Its structured damage descriptions show how observations are standardized across locations.
Giuseppe Mercalli: An Italian volcanologist and seismologist who developed an earthquake intensity scale in 1902. His scale helped establish the tradition of rating earthquakes by observed effects.
Earthquake early warning: A system that detects an earthquake’s seismic waves and alerts areas before stronger shaking arrives. Intensity forecasts and observations help communicate the expected local effects of shaking.
Peak ground acceleration: The largest acceleration recorded at a site during a period of ground shaking. It is a physical measurement, whereas many intensity ratings summarize observed effects.