The Rossi–Forel scale was one of the first seismic scales to reflect earthquake intensities. Developed by Michele Stefano Conte de Rossi of Italy and François-Alphonse Forel of Switzerland in the late 18th century, it was used for about two decades until the introduction of the Mercalli intensity scale in 1902.
The 1873 version of the Rossi–Forel scale had 10 intensity levels:
- I. Microseismic tremor. Recorded by a single seismograph or by seismographs of the same model, but not by several seismographs of different kinds. The shock felt by an experienced observer.
- II. Extremely feeble tremor. Recorded by several seismographs of different kinds. Felt by a small number of persons at rest.
- III. Feeble tremor. Felt by several persons at rest. Strong enough for the direction or duration to be appreciable.
- IV. Slight tremor. Felt by persons in motion. Disturbance of movable objects, doors, windows, cracking of ceilings.
- V. Moderate tremor. Felt generally by everyone. Disturbance of furniture, ringing of some bells.
- VI. Strong tremor. General awakening of those asleep. General ringing of bells. Oscillation of chandeliers, stopping of clocks, visible agitation of trees and shrubs. Some startled persons leaving their dwellings.
- VII. Very strong tremor. Overthrow of movable objects, fall of plaster, ringing of church bells. General panic. Moderate to heavy damage buildings.
- VIII. Damaging tremor. Fall of chimneys. Cracks in the walls of buildings.
- IX. Devastating tremor. Partial or total destruction of buildings.
- X. Extremely high intensity tremor. Great disaster, ruins, disturbance of the strata, fissures in the ground, rock falls from mountains.
- Tiedemann, Herbert (1992). Earthquakes and Volcanic Eruptions. A Handbook on Risk Assessment. Zurich: Swiss Reinsurance Company.