Glossary

Intensity (Mercalli Scale)

Intensity describes what people feel and the damage observed at a given place. It is written in Roman numerals, from I (not felt) to XII (total destruction), on the Modified Mercalli scale. A single earthquake has one magnitude but a different intensity depending on the location.

Above intensity VI, shaking is strong and the first damage appears. From VIII, weak buildings collapse. The USGS collects reports from residents through its "Did You Feel It?" survey, shown in the earthquake cards.

Examples on the Map

• 2011 Tōhoku Earthquake and Tsunami
• Major Earthquakes Since 1900

Other Definitions

• Tectonic Plate
• Subduction
• Mid-Ocean Ridge
• Transform Fault
• Fault
• Earthquake, Epicentre and Hypocentre
• Magnitude
• Aftershock
• Tsunami
• Active Volcano
• Stratovolcano
• Shield Volcano
• Caldera
• Volcanic Explosivity Index (VEI)
• Pyroclastic Flow
• Lahar
• Hotspot
• Tropical Cyclone, Hurricane, Typhoon
• Saffir-Simpson Scale
• Aurora and Kp Index