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Plate Tectonics
Plate tectonics refers to any movement of the earth's crust over the liquid mantle below it. The surface of the earth is constantly moving at an extremely slow rate, and the shifting of continental plates has shaped how the continents look over millions of years. When the shifting plates move against each other, this can lead to earthquakes. Plate tectonics are the driving force behind earthquakes, as well as other natural disasters, such as volcanoes and tsunamis.
Plate Boundaries
There are four different types of interaction when two plates are next to each other. Divergent plates are moving apart, so they are more likely to cause volcanoes than earthquakes, since molten material under the plates can move up into the opening crack. At convergent boundaries, one plate slips under the other, a process called subduction. This can lead to large earthquakes, especially when pressure builds up and a big slip happens all at once. Transform boundaries appear when two plates shift past each other in opposite directions, another potential source of earthquakes. In some places, there is a plate boundary zone, where the interaction between two plates remains unclear, so the potential for earthquakes is unknown.
Specific Mechanism
The stresses that build up as two plates interact with each other is the direct cause of earthquakes. Just like when any two objects push up against each other, eventually the building force causes one or both of the objects to break. In the case of tectonic plates, this break sends tremors upward and outward through the earth, causing the shaking and rolling felt as an earthquake. The longer the stresses have been building up without being released, the greater the potential energy in the two plates, and the more likely they will rupture in a big earthquake event.
Predictability
Because scientists can identify areas where plate boundaries are building up stress, they can predict areas where earthquakes are most likely. They can also pinpoint the speed of the crustal movement using satellite data. Using this information, scientists know that about 90 percent of the earth's earthquakes will occur along well-known fault lines and subduction zones, explains the Earthquake Information Bulletin by the U.S. Geologic Service. However, earthquake science still isn't good enough to predict the date or time of a particular earthquake.