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Compared on Richter Scale
In the U.S., scientists compare the magnitude of earthquakes using an updated version of the Richter scale. While technically dubbed the ̶0;Moment Magnitude Scale,̶1; it is still commonly referred to as the Richter scale since it yields results which are similar to those of the Richter scale, with the only primary difference being calculation methodology. Although the scale has no precise lower or upper limits, scientists most often use to it classify earthquakes on a scale ranging from 2.0 to 9.0; however, the world̵7;s most powerful earthquakes exceed 9.0. The higher the number, the stronger the quake. For example, an earthquake measuring 2.5 generally isn̵7;t even noticeable; an earthquake measuring 5.8 would be considered moderate, and an earthquake measuring 8.2 could be catastrophic. It is important to note that the Richter scale is an exponential scale; for instance, an earthquake measuring 6.0 is 10 times stronger than one measuring 5.0, and an earthquake measuring 7.0 is 100 times stronger than one measuring 5.0.
Strongest Earthquake Recorded in Chile
As of the time of this publication, the most powerful earthquake ever recorded occurred in Chile in 1960. It measured a magnitude 9.5 on the Richter scale. The strongest earthquake ever recorded in the U.S. registered a 9.2. It occurred in Alaska in 1964.
Usually Occur Near Plate Boundaries
The majority of noteworthy earthquakes occur along the borders of tectonic plates. The world has seven major plates, named after the continents or oceans which overlay them, as well as considerably smaller plates. These plates aren̵7;t motionless -- they crash into each other, pull away from each other or slide past one another along lines called faults. Nor do they move necessarily smoothly -- tension can build up within the plates over time, until they instantaneously move a significant distance -- an earthquake.
Can Happen in Other Locations
Earthquakes can sometimes take place far away from plate boundaries. For instance, earthquakes occur in the East African Rift zone, where it appears that the African plate is trying to split itself in two. In the U.S., destructive earthquakes have occurred in New Madrid, Missouri and Charleston, South Carolina, both of which lie squarely within the bounds of the North American plate.
Originate at Different Depths
Although their effects may be felt quite strongly on the surface of the Earth, earthquakes do not actually originate on the surface itself -- they start underground. Different earthquakes take place at different depths, some just below the surface, and others up to 800 kilometers (about 500 miles) beneath. The majority of earthquakes, however, stem from locations less than 80 kilometers (50 miles) from the surface.
Have an Epicenter and Hypocenter
When the news media refers to a certain location as being the ̶0;epicenter̶1; of an earthquake, they are referring to the point at the Earth̵7;s surface directly above the spot where the fault ruptured. That spot is itself known as the hypocenter, the true point of origin of the earthquake.
Cannot Be Predicted
Unlike the weather, earthquakes are unpredictable and occur without warning. They can happen during any season and at any time of day. However, by analyzing statistics, scientists can provide general long-range probabilities of an earthquake occurring in vulnerable areas. For instance, scientists may posit that there is a 70 percent chance of a major earthquake taking place along a certain fault line within the next 50 years.
Can Be Deadly
Earthquakes have the potential to claim unfathomable amounts of lives. The deadliest earthquake on record, which struck China in 1556, killed upwards of 800,000 people. More recently, a 1976 earthquake in China claimed more than 250,000 lives. Most deaths in earthquakes are attributable to collapsing structures.
Can Generate Tsunamis
Underwater or coastal earthquakes are the most common cause of tsunamis, fast-moving ocean waves which can inundate coastlines, causing significant property damage and loss of life. They form when a hefty volume of water is suddenly displaced. Tsunamis travel at the speed of commercial aircraft, and can reach heights of over 30 meters (100 feet). Like the earthquakes which produce them, tsunamis can strike with little to no warning. However, when a potentially tsunami-generating earthquake occurs, scientists can pinpoint far-flung areas that a tsunami could eventually strike, possibly providing time for authorities to issue warnings and affording people the chance to escape to safety.
Are Common
Not all earthquakes are dangerous, however. The U.S. Geological Survey estimates that there are 500,000 earthquakes in the world each year. Most are extremely weak, though -- only about one-fifth of them are even perceptible to humans.