EARTHQUAKES 

One of the most frightening and destructive phenomena of nature is a severe earthquake and its terrible aftereffects.

Earthquakes strike suddenly, violently, and without warning at any time of the day or night. If an earthquake occurs in a populated area, it may cause many deaths and injuries and extensive property damage.

Although there are no guarantees of safety during an earthquake, identifying potential hazards ahead of time and advance planning can save lives and significantly reduce injuries and property damage.

Some 80 percent of all the planet's earthquakes occur along the rim of the Pacific Ocean, called the "Ring of Fire" because of the preponderance of volcanic activity there as well. Most earthquakes occur at fault zones, where tectonic plates; giant rock slabs that make up the Earth's upper layer; collide or slide against each other. These impacts are usually gradual and unnoticeable on the surface. However, immense stress can build up between plates. When this stress is released quickly, it sends massive vibrations, called seismic waves, often hundreds of miles through the rock and up to the surface. Other quakes can occur far from faults zones when plates are stretched or squeezed.

Scientists assign a magnitude rating to earthquakes based on the strength and duration of their seismic waves. A quake measuring 3 to 5 would be considered minor or light; 5 to 7 is moderate to strong; 7 to 8 is major, and 8 or more is great.

On average, a magnitude 8 quake strikes somewhere every year and some 10,000 people die worldwide annually in earthquakes. Collapsing buildings claim by far the majority of lives, but the destruction is often compounded by mud slides, fires, floods, or tsunamis. Smaller temblors that usually occur in the days following a large earthquake can complicate rescue efforts and cause further death and destruction.

Loss of life can be avoided through emergency planning, education, and the construction of buildings that sway rather than break under the stress of an earthquake.

How can I protect myself from an earthquake?

• What to do before an earthquake
• What to do during an earthquake
• What to do after an earthquake
• Earthquake Terms