Glossary
Magnitude
Magnitude measures the energy released by an earthquake at its source. It is a logarithmic scale. One step up means about 32 times more energy, and two steps about 1,000 times. A magnitude 9 earthquake therefore releases roughly a million times more energy than a magnitude 5.
Seismologists now mostly use moment magnitude (Mw), which stays reliable for very large earthquakes. The old Richter scale saturates above about 7. Magnitude does not tell the whole story of damage, which also depends on depth, distance and buildings.
Examples on the Map
Other Definitions
- Tectonic Plate
- Subduction
- Mid-Ocean Ridge
- Transform Fault
- Fault
- Earthquake, Epicentre and Hypocentre
- Intensity (Mercalli Scale)
- 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