The energy from this movement travels as seismic waves along the ground surface and within the crust. The arrival of this released energy is felt as an earthquake. The measure of an earthquake's strength is expressed as magnitude, and is determined by using an instrument called a seismograph. The best known magnitude scale is one designed by C.F. Richter in 1935 for west coast earthquakes. An earthquake's intensity is determined by observing its effects at a particular place on the Earth's surface.
Intensity depends on the earthquake's magnitude, the distance from the epicenter, and local geology.
These scales are based on reports of people awakening, felt movements, sounds, and visible effects on structures and landscapes. The most commonly used scale in the United States is the Modified Mercalli Intensity Scale , and its values are usually reported in Roman numerals to distinguish them from magnitudes. TOP Past damage in New Jersey New Jersey doesn't get many earthquakes, but it does get some. Fortunately most are small. A few New Jersey earthquakes, as well as a few originating outside the state, have produced enough damage to warrant the concern of planners and emergency managers.