Earthquake Intensity and the Richter Scale
Earthquakes occur due to the activity of forces, energy, stored deep within the Earth's interior. These forces are constantly affecting the surface of the Earth, forming mountains, valleys, ridges etc. When the energy stored within the Earth is suddenly released, for example by shearing movements along faults in the crust of the Earth, an earthquake results. The area of the fault where the sudden rupture takes place is called the focus point or hypocenter. The point on the Earth's surface directly above the hypocenter is called the epicenter of the earthquake. The closer you are to the epicenter of the earthquake, the more dangerous and devastating.
The severity of an earthquake can be expressed in terms of both intensity and magnitude. Although the two terms are very different, they are often confused with each other. Intensity is based on the observed effects taken place during the earthquake, for instance the ground shaking underneath people, buildings, and natural features. The intensity varies from place to place within the disturbed region depending on the location of the observer with respect to the epicenter of the earthquake. The magnitude of an earthquake is related to the amount of seismic energy released at the hypocenter of the earthquake. The magnitude is based on the amplitude of the seismic waves recorded by a seismograph; all seismographs have a common calibration. Therefore the magnitude of an earthquake is represented by a single, instrumentally determined value.
The Richter magnitude scale was invented in 1935 by Charles Richter of the California Institute of Technology. The Richter scale was developed as a mathematical device to compare the size of earthquakes. The magnitude of an earthquake is determined from the logarithm of the amplitude of waves recorded by seismographs. On the Richter scale, magnitude is expressed in whole numbers and decimal fractions. For...