Which scale classifies earthquake effects from I, not felt, to XII, total destruction?

The Modified Mercalli intensity scale classifies earthquake effects from I, not felt, to XII, total destruction.

Unlike a magnitude scale, which describes the size of an earthquake at its source, the Modified Mercalli scale describes observed shaking and damage at a particular location. Its twelve Roman-numeral levels range from I, meaning the event is generally not felt, to XII, representing total destruction.

Intensity can vary widely during the same earthquake. Places near the epicenter may experience severe effects, while distant locations may feel weak shaking. Local geology, building quality, distance, and depth all influence the reported intensity.

The scale is based on observations rather than a single instrument reading. Consequently, one earthquake has one approximate magnitude but many intensities across the affected region.