Largest Historical Earthquakes

Earthquakes are caused by the sudden release of energy in the Earth's crust, usually due to the movement of tectonic plates. When stress accumulates along a fault line faster than it can be released through slow creep, the rocks eventually fracture and slip, generating seismic waves that we feel as an earthquake.

Earthquakes are measured using seismographs that detect ground motion. The magnitude (energy released) is calculated using various scales including the moment magnitude scale (Mw), which has replaced the Richter scale for most purposes. Intensity (effects on people and structures) is measured using the Modified Mercalli Intensity (MMI) scale.

Magnitude measures the total energy released by an earthquake at its source — each earthquake has only one magnitude. Intensity measures the strength of shaking at a specific location, which varies with distance from the epicenter, local geology, and building construction. The same earthquake can have different intensities at different locations.

Currently, earthquakes cannot be reliably predicted in terms of specific time, location, and magnitude. Scientists can identify areas of higher probability based on fault behavior and historical patterns, but precise prediction remains beyond current scientific capability. Early warning systems can provide seconds to minutes of alert after an earthquake begins.

Follow the Drop, Cover, and Hold On protocol: Drop to your hands and knees, take Cover under a sturdy piece of furniture, and Hold On until the shaking stops. Stay away from windows and exterior walls. Do not run outside during shaking. If outdoors, move to an open area away from buildings, trees, and power lines.