Earthquakes 2 Essay, Research Paper
Earthquakes can simply be defined as a naturally induced shaking of the ground caused by the fracture and sliding of rock within the earth’s crust. There are at least 6,000 earthquakes detected throughout the world each year. Many people have heard about or experienced first hand the effects that an earthquake can have. But many people don’t understand what causes them and what exactly is happening during an earthquake. In the following paper I will be explaining the causes and effects of earthquakes.
There are at least 6,000 earthquakes detected throughout the world each year. Of these 6,000 about 5,500 are either too small or too far away from populated areas to be felt. About 450 of these estimated 6,000 are felt but cause no damage and about 35 cause minor damage. The remaining 15, however, can take great tolls in death and suffering.
When an earthquake occurs, the earth’s crust breaks along a surface known as a fault plane. Faults are not always visible at the surface of the earth. A fault is a fracture within a rocky mass within the earth’s crust. The depth and the length of faults vary tremendously. Earthquakes are caused by faults that are active. An active fault is a fault along which the two sides of the fracture move with respect to each other. An earthquake is caused by the sudden movement of the two sides of the fault.
Faults are divided into three main groups, depending on how they move. There are normal faults which occur in response to pulling or tension. There are thrust faults which are caused as a result of squeezing or compression. The third group is strike-slip faults which are caused as a result of either type of stress.
Some earthquakes tremendously effect the earth. No earthquake is exactly alike another so the effects vary depending on the part of the world the earthquake occurred and the size of the earthquake. One effect that earthquakes have is strong ground motion. Strong ground motion is a result of seismic waves reaching the earth’s surface. Another effect is post-earthquake fires which are a secondary effect of strong ground motion. Ground failure and landslides are both effects of an earthquake mainly caused by strong ground motion. Tsunamis which are immense sea waves occur when earthquakes happen beneath the ocean floor.
To determine the strength and location of an earthquake scientists use a seismograph. A seismograph is an instrument which is equipped with sensors that can detect ground motions caused by seismic waves both near and far away. The scientists which measure this seismic ground movement are called seismologists. Seismologists measure seismic ground movements in three directions. These three directions are up and down; north and south; and east and west. The seismologists use the Richter scale to gauge the intensity of the earthquakes.
Earthquakes are clearly a destructive act of nature. You now have learned about the possible effects of earthquakes. You have learned how they are caused and how they are recorded and measured. In the following pages you will find charts and tables which outline some of the greatest earthquakes of the 20th century and useful earthquake terminology.