Earthquake

Natural Disasters - Earthquake Earthquakes are caused by a sudden shift / movement deep under ground in the Earth's tectonic plates. On the surface, we see this as the shaking of the ground, causing damage to poorly built structures. The most powerful earthquakes can destroy even the best built structures. Earthquakes can also cause other disasters including tsunamis and volcanic eruptions. Earthquakes occur unpredictably along fault lines, capable of killing thousands of people. Seismometers can detect the strength of an earthquake. It gives a number on the Richter scale devised by Charles Richter: Descriptor Richter magnitudes Earthquake Effects Frequency of Occurrence Micro Less than 2.0 Microearthquakes, not felt. About 8,000 per day Very minor 2.0-2.9 Generally not felt, but recorded. About 1,000 per day Minor 3.0-3.9 Often felt, but rarely causes damage. 49,000 per year (est.) Light 4.0-4.9 Noticeable shaking of indoor items, rattling noises. Significant damage unlikely. 6,200 per year (est.) Moderate 5.0-5.9 Can cause major damage to poorly constructed buildings over small regions. At most slight damage to well-designed buildings. 800 per year Strong 6.0-6.9 Can be destructive in areas up to about 100 miles across in populated areas. 120 per year Major 7.0-7.9 Can cause serious damage over larger areas. 18 per year Great 8.0-8.9 Can cause serious damage in areas several hundred miles across. 1 per year Rare great 9.0 or greater Devastating in areas several thousand miles across. 1 per 20 years Examples of earthquakes include: 1976 Tangshan 2004 Indian Ocean earthquake Damage from the 1906 San Francisco earthquake. Section of collapsed freeway after the 1989 Loma Prieta earthquake. Global earthquake epicenters, 1963–1998