Where Do Earthquakes Occur?

An earthquake is the release of sudden and extreme energy that occurs in the Earth’s crust. This energy then creates seismic waves, which humans feel on the Earth’s surface. Using a seismometer, the strength of an earthquake can be recorded and measured. The Mercalli scale is used to measure the earthquake and anything seven or above is considered extremely dangerous.

Earthquakes usually occur along fault lines, or cracks that occur within the Earth’s crust. The crust is actually not one continuous substance, but it is divided into giant plates. These plates aren’t sedentary; rather, they move throughout the year—although they may only move a few inches over many years. When these moving plates collide, or brush up against each other, pressure builds and an earthquake can occur.

Faults are specifically located where there is a fracture in the rock, and the rock on one side of this fracture has moved against the rock on the other side of the fracture.

The areas where there are active fault zones are the areas where earthquakes will most likely occur. These fault lines, and more broadly fault zones, are all across the world, although some fault lines are more dangerous than others.

Pacific Rim of Fire Fault Zone

Japan, New Zealand, Alaska are all located on one side of a horseshoe-shaped fault line that circles the Pacific Ocean and is responsible for frequent earthquakes and frequently erupting volcanos. This highly siesmic area, called the Ring of Fire, is very active resulting in the movement of the various Pacific plates. It causes frequent earthquakes in Japan as well as earthquakes throughout the Pacific Ocean area including the San Andreas Fault area on the other end of the horseshoe-shaped fault area. This zone was responsible for the devastating earthquakes in Indonesia in 2004, in New Zealand in early 2011 as well as a 9.0+ quake and a series of offshore earthquakes in Japan in early 2011 which also resulted in a tsunami.

San Andreas Fault

The San Andreas Fault is a fault line that stretches about one thousand and three hundred kilometers through California in the United States, and through Baja California in Mexico. It’s specifically classified as a continental transform fault, and it moves in a horizontal motion that is scientifically known as a right-lateral strike-slip. This fault line occurs between the Pacific Plate and the North American Plate.

The fault was discovered in 1895 by a professor at Berkeley, named Andrew Lawson. This fault can be traced all the way back to the Cenozoic period. It is one of the longest faults in which the plates of the Earth are sliding across each other in a horizontal movement. This fault has been the cause behind a number of significant earthquakes, such as the San Francisco Earthquake in 1906, and the Loma Prieta Earthquake in 1989.

Hayward Fault Zone

The Hayward Fault Zone stretches to just about sixty kilometers, along the western base of hills on the east of the San Francisco Bay. Unfortunately, the fault zone cuts across several areas which are densely populated with people, such as the locations of Richmond and Berkeley. This zone runs parallel to the San Andreas Fault.

The Hayward Fault Zone refers to the area that encompasses the overall motion between the Pacific Plate and the North American Plate. The Hayward Fault Zone was the cause behind such earthquakes as the Hayward earthquake of 1868 which had a magnitude of seven. This earthquake occurred at the south of the fault zone.

The Enriquillo-Plantain Garden Fault Zone

The Enriquillo-Plantain Garden Fault Zone refers to an area of movement between the North American and the Caribbean tectonic plates, and encompasses about twenty millimeters of lateral movement between the plates each year.

This fault zone was behind a number of different earthquakes throughout history, including the recent earthquake in Haiti in January of 2010. Previously, this zone was also responsible for a 7.5 magnitude earthquake that occurred in 1692 and almost destroyed all of Port Royal.

Septentrional-Oriente Fault Zone

The Septentrional-Oriente Fault Zone stretches across the north of Hispaniola, near the Dominican Republic and Haiti. It refers to an area of motion between the North American tectonic plates and the Caribbean tectonic plates, sharing approximately half of this motion with the fault zone discussed directly above. This fault zone also contains what geologists refer to as a number of lateral moving strike slip faults. This zone was responsible for the fault that decimated the city of Cap-Haitien in 1842.