Earthquakes have damaging effects on life, homes and property. However, an earthquake also has an effect on the environment. Damage to the environment during an earthquake can cause devastation and loss of life beyond that caused in the original event, and organisations such as the Federal Emergency Management Agency work to target areas most likely to be affected.
When large faults rupture and an earthquake occurs, areas of the ground often form large cracks at the surface. Some of the ground failure occurs during intense shaking of the land near large or secondary faults. Other ground failure is caused by liquefaction, a process in which wet soil weakens and turns to liquid due to pressure from the earth shaking. Soil that lacks stiffness, such as sandy soil, is most likely to liquefy.
Landslides occur when weak rock and soil collapse during an earthquake. Common types of landslides that occur in mountainous and hilly areas are shallow rockfalls, rock slides, slumps and block slides. Massive amounts of soil, rock and vegetation slide downhill, often destroying objects in their path, blocking streams and filling valleys. Landslides can cause massive clouds of dust that lead to infection with the spores of the fungus Coccidioides immitis, a deadly disease known as Valley Fever or coccidioidomycosis.
Seismic waves from earthquakes often cause tsunamis, or tidal waves. These powerful waves start deep in the ocean and usually go unnoticed until they reach shallow water. The tall waves damage areas along the sea when they travel far inland and carry objects in their path back out to sea. Aftershocks can cause new tsunamis to form and hit land before communities have a chance to recover from the original damage.
A seiche is a large wave that moves up and down instead of forward. Seiches occurs when water in a closed space sloshes back and forth with enough force to overflow and damage structures near lakes, reservoirs, bays and harbours. Swimming pools often oscillate and overflow during earthquakes, affecting nearby land.
Much earthquake damage is caused by secondary effects of man-made materials on the environment. Broken water pipes can flood land, and ruptured gas, electrical and fuel lines lead to fire. Hazardous material spills introduce sewage, medical, radioactive and poisonous material into the air, water and earth. The explosions in nuclear plants following the March 2011 earthquake in Japan that released radioactive material into the air is an example of a secondary effect.