What natural disaster is measured using the Modified Mercalli Intensity scale?

The Modified Mercalli Intensity scale is specifically designed to measure the intensity of earthquakes based on observed effects and damage. This scale categorizes the experience of an earthquake from "not felt" to "total destruction," taking into account the human perception and structural damage caused by the seismic event. Unlike seismic scales that measure physical parameters like magnitude, the Modified Mercalli Intensity scale focuses on the impact of the earthquake on people, buildings, and the Earth’s surface.

Other natural disasters listed, such as tsunamis, volcanoes, and floods, are assessed using different metrics and scales that are more suited to their specific characteristics and impacts. For instance, tsunamis are measured in terms of wave height and inundation, while volcanoes are evaluated based on eruption type, volume of material erupted, and the volcanic explosivity index. Floods are typically assessed based on water depth and extent of inundation, not intensity in the same context as earthquakes. Therefore, the Modified Mercalli Intensity scale's focus on the effects and experiences related uniquely to earthquakes makes it the correct answer.