These shifting plates generate energy that is referred to as seismic waves. These waves shift outward just like waves that are created by a disturbance in a body of water
You can find different kinds of seismic waves. Body waves travel below the Earthís surface, via liquids, gas and solids. Main body waves are the quickest. Once they reach the surface they become surface waves and they carry on traveling above the ground. Secondary body waves come after the main waves and do not reach the surface. Surface waves are the slowest waves. They cause the most intense shake and damage at the finish of an earthquake.
Natural events including volcanic eruptions and meteor impacts can cause earthquakes, however the majority of naturally taking place earthquakes are triggered by motion of the earth's plates.
The surface of the earth is composed of 20 constantly shifting plates. As the plates shift, tension is produced and as its strength raises it can cause the crust to break. Whenever a break occurs, the stress is introduced as energy that moves via the Earth in the type of waves. These waves are earthquakes.
The National Earthquake Information Center (NEIC) records an average of 20,000 earthquakes annually (about 50 a day) across the world. You can find, however, millions of earthquakes estimated to happen annually that are too weak to be recorded.
Almost 80 % of all the earth's earthquakes occur along the rim of the Pacific Ocean, known as the Ring of Fire; an area that circles the Pacific Ocean and is residence to 452 volcanoes (over 75 % of the world's active and dormant volcanoes).
Every year the southern California area has around 10,000 earthquakes; the majority of which go unseen. If there is a big earthquake, however, the aftershock sequence will generate many more earthquakes of most magnitudes for months.
The biggest recorded earthquake in america was a magnitude 9.2 that struck Prince William Sound, Alaska on March 28, 1964.
Earthquakes take place all the time all around the world, both along faults and along plate edges.
Along Plate Edges
Many earthquakes happen along the edge of the oceanic and continental plates. The world's crust is comprised of several pieces, referred to as plates. The plates below the oceans are known as oceanic plates and the rest are continental plates. The plates are moved around by the movement of a deeper part of our planet (the mantle) that lies below the crust. These plates are usually bumping into one another, past each other or pulling away from one another. The plates generally move at about the identical speed that your fingernails grow. Earthquakes usually happen where two plates are sliding past each other or running into each other.
Earthquakes can also happen away from the edges of plates, along faults. Faults are cracks in our planet in which sections of a plate (or two plates) are shifting in various directions. Faults are due to all that sliding and bumping the plates do. They are more common close to the edges of the plates.