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An earthquake is caused by a sudden slip on a fault. The tectonic plates are always slowly moving, but they get stuck at their edges due to friction. When the stress on the edge overcomes the friction, there is an earthquake that releases energy in waves that travel through the earth's crust and cause the shaking that we feel.
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- Overview
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Over the centuries, earthquakes have been responsible for millions of deaths and an incalculable amount of damage to property. Depending on their intensity, earthquakes (specifically, the degree to which they cause the ground’s surface to shake) can topple buildings and bridges, rupture gas pipelines and other infrastructure, and trigger landslides, tsunamis, and volcanoes. These phenomena are primarily responsible for deaths and injuries. Very great earthquakes occur on average about once per year.
What are earthquake waves?
Earthquake waves, more commonly known as seismic waves, are vibrations generated by an earthquake and propagated within Earth or along its surface. There are four principal types of elastic waves: two, primary and secondary waves, travel within Earth, whereas the other two, Rayleigh and Love waves, called surface waves, travel along its surface. In addition, seismic waves can be produced artificially by explosions.
How is earthquake magnitude measured?
Magnitude is a measure of the amplitude (height) of the seismic waves an earthquake’s source produces as recorded by seismographs. Seismologist Charles F. Richter created an earthquake magnitude scale using the logarithm of the largest seismic wave’s amplitude to base 10. Richter’s scale was originally for measuring the magnitude of earthquakes from magnitudes 3 to 7, limiting its usefulness. Today the moment magnitude scale, a closer measure of an earthquake’s total energy release, is preferred.
Where do earthquakes occur?
Earth’s major earthquakes occur mainly in belts coinciding with the margins of tectonic plates. This has long been apparent from early catalogs of felt earthquakes and is even more readily discernible in modern seismicity maps, which show instrumentally determined epicentres. The most important earthquake belt is the Circum-Pacific Belt, which affects many populated coastal regions around the Pacific Ocean—for example, those of New Zealand, New Guinea, Japan, the Aleutian Islands, Alaska, and the western coasts of North and South America. It is estimated that 80 percent of the energy presently released in earthquakes comes from those whose epicentres are in this belt. The seismic activity is by no means uniform throughout the belt, and there are a number of branches at various points. Because at many places the Circum-Pacific Belt is associated with volcanic activity, it has been popularly dubbed the “Pacific Ring of Fire.”
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A second belt, known as the Alpide Belt, passes through the Mediterranean region eastward through Asia and joins the Circum-Pacific Belt in the East Indies. The energy released in earthquakes from this belt is about 15 percent of the world total. There also are striking connected belts of seismic activity, mainly along oceanic ridges—including those in the Arctic Ocean, the Atlantic Ocean, and the western Indian Ocean—and along the rift valleys of East Africa. This global seismicity distribution is best understood in terms of its plate tectonic setting.
Oct 18, 2022 · Earthquakes are one of Earth's biggest and deadliest natural disasters. Here we explore earthquakes in more detail while uncovering how and why they happen.
Oct 19, 2023 · Hundreds of earthquakes occur on Earth everyday. Most of them are small, barely detectable by most people. But occasionally there is a much more significant quake. On average, a major earthquake —one with a magnitude of 7.0-7.9—strikes somewhere on the planet more than once a month.
6 hours ago 2.0 magnitude, 3 km depth. Inverness , California , United States. 6 hours ago 1.6 magnitude, 27 km depth. Colorado City , Arizona , United States. ← Previous 1 2 3 4 5 6 7 8 9 …. Next →. Earthquake locations and epicenters today and in the last few days - the most recent earthquakes.
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Credit: © Agata Nowicka/Marlena Agency for Caltech Science Exchange. While tectonic earthquakes can occur at any location around the world, the majority of large earthquakes—about 80 percent—occur at the circum-Pacific seismic belt found along the rim of the Pacific Ocean.
