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How are earthquakes formed? Earthquakes have been disrupting human civilization for centuries. Believe it or not, some archeologists now think that earthquakes were at the root of all major societal changes in the ancient world. Earth Science professors at Stanford University have shown archeological evidence that earthquakes could have caused the downfall of civilizations in Central America, the Eastern Mediterranean, and South Asia in the ancient world.
Unfortunately, we have not escaped the destabilizing power of the earthquake in modern times. Everyone’s first line of defense is to know all about earthquakes and have a full-proof safety plan in case one erupts unexpectedly. In this article, we’ll answer basic questions like how are earthquakes formed, plus we’ll give you a few tips to prepare yourself for one.
What Is An Earthquake?
People often define earthquakes as a sudden and violent shaking of the earth’s surface. If you’ve ever felt an earthquake before, you’ll be aware of these symptoms. But what is really taking place in the earth to cause these earthquakes? How are earthquakes formed? Well, earthquakes usually occur when two blocks of the earth violently slip apart. Geologists call the area of the slip a “fault plane.” The epicenter of the quake occurs on the surface of the earth, whereas the hypocenter of the earthquake is down below wherever the earthquake originated.
You might notice some foreshocks before the real earthquake begins. These foreshocks are much smaller than the actual earthquake, and they only affect a small portion of the earth’s surface. The term “main shock” is used to describe the full impact of the earthquake. After the main shock, you’re most likely going to experience some aftershocks from the earthquake. These aftershocks can last days, weeks, months, or years, depending on the strength of the earthquake.
The United States Geological Survey (USGS) estimates that over 500,000 detectable earthquakes occur around the world each year. We can feel about 100,000 of these earthquakes on the surface of our earth. Generally, 100 of them do massive damage. Geologists today are blessed with best seismographic technology, however, it’s just not enough.
How Are Earthquakes Formed?
To answer the question “how are earthquakes formed,” we have to learn a bit more about some basic geology. There are four major layers of the earth that you’ve probably already heard of: the inner core, the outer core, the mantle, and the crust. When looking at a geological drawing, you can see that the mantle and crust on our earth’s surface are both extremely thin. Not only are these layers thin, they are split up into various pieces we call “tectonic plates.” Located at the edge of each of these plates are “plate boundaries.”
Plates can either be oceanic or continental. Oceanic plates are, as the name suggests, under the ocean, and continental plates are above the ocean. Tectonic plates have always been moving against each other from time immemorial. Since these tectonic plates rub against each other so much, it makes sense that most earthquakes occur on their boundaries.
So, the simple answer to the question “how are earthquakes formed” is “the movement of tectonic plates.” These boundary areas have many faults, which causes a greater number of earthquakes on the earth’s surface. Once two faults get stuck, the blocks continue to move, and the energy once used to slide against each other causes the whole earth’s surface to shake. After the two plates finally release, all of that energy is let out on the earth’s surface. Now you finally know how to answer the question “how are earthquakes formed?”
Where Do Earthquakes Occur Most Often?
When looking at a map of fault lines around the world, it is quite easy to see what countries, nations, and states face a great earthquake risk. As we saw in our section on “how are earthquakes formed,” you should expect the most powerful earthquakes to occur by fault lines. For example, there’s a fault line going right through New Zealand. New Zealand has experienced 30,958 earthquakes in the past year alone.
In the U.S.
In terms of the USA, it might surprise some people that Alaska is the number one state when it comes to earthquakes. The USGS says that the earthquakes in Alaska often go underreported. Alaska experiences about 50 percent of all the earthquakes in the USA. They often range in magnitude between 3.5 and 4.0. Unfortunately, the world’s most destructive earthquakes have occurred in The Last Frontier.
Almost all of most powerful earthquakes in the world occurred in Alaska, including the most destructive earthquake of all: the 1964 Great Alaska Earthquake. It had a magnitude of 9.2, caused a tsunami, killed 131 people, and caused $2.3 billion dollars in property loss. Other huge earthquakes that have occurred in Alaska include the Rat Islands Earthquake of 1965 (magnitude 8.7), the Andreanof Islands Earthquake in 1957 (magnitude 8.6), and the Shumagin Islands Earthquake of 1938 (magnitude 8.2).
The number two state on the USGS’s list, California, won’t surprise most people. How are earthquakes formed in California, you may ask? Well, the San Andreas Fault runs along the entire side of the Golden State. The very first earthquake recorded in this region took place in 1769 near Los Angeles. The Gaspar de Portola exploratory group recorded this first of many earthquakes in the region.
Scientists estimate that southern California has around 10,000 earthquakes annually. A few hundred of these earthquakes are above a magnitude of 3.0, and only about 15 are above a 4.0. The most powerful earthquake to have ever occurred in California was the 7.9 magnitude Fort Tejon Earthquake in 1857.
A Word of Ending
Earthquakes can occur anywhere at anytime. No matter where you live, it’s a good idea to prepare yourself for the worst-case scenario. You should have all your critical medications, documents, and supplies of water stored in a safe area. Always inquire whether a building is earthquake proof before working or living there. Once you start to feel the trembling of an earthquake, it’s important to secure heavy and/or dangerous items so they won’t injure anyone.
The most important things to remember during an earthquake are to “drop, cover, and hold on.” This phrase means, drop to your hands and knees, cover your head and neck, and hold on to something sturdy until the tremors stop. People in cars should stay in them until the earthquake passes. Earthquakes are a natural occurrence, but they can cause great damage if we’re not vigilant. Be sure you have a plan to keep you and you loved ones safe in case of an earthquake.