Earthquakes 

Earthquakes, that can cause the ground to shake and buildings to sway and even tumble to the ground are definitely serious events, but why and how they occur provides some brilliant insight into the world that exists deep beneath our feet.

An earthquake actually happens many more times than we realize, but most of these are very minor movements that barely register on the seismographs, which are the recording instruments, used to monitor the movements deep underground. There may be as many as 500,000 earthquakes a year but only part of these is really noticeable. It is when the tremors or shaking activity is strong enough to feel that it gets the attention of many people.

When two sections of earth are aligned at slightly different levels, this is called a fault, and when these two sections suddenly move and slide over or past one another, this creates motion deep within the earth. This spot inside the earth is known as the hypocenter and the site that is located directly above the hypocenter is known as the epicenter. It is the epicenter where the shaking and quaking motion is noticeable to us. The epicenter is also the location that has the most damage, although the damage and motion may be obvious for great distances.

While the main shock is what we associate most with earthquakes, there are some other earth motions to be familiar with. Foreshocks are tremors deep in the ground that occur before an actual earthquake happens. The trembling of the foreshocks alert scientists to the activity that is going on in one location deep inside the earth but until the main shock happens they do not know if these early, small rumbling quakes are only movements in the earth or signs of a quake that is about to happen.

This is also an area of intense study and research because it would be of tremendous value to be able to use foreshocks to predict the larger quakes before they happen. Aftershocks are tremors and smaller earthquakes that occur after the main shock, and while smaller than the big quake they follow, they can still create a lot of damage because many buildings have already been weakened at this time. These aftershocks will happen in the same area as the main quake and they can continue for days, or even months or years.

Let’s take a look and see what actually happens inside the earth during an earthquake. There are 4 main layers that create our planet. The top layer is the crust, and the mantle is located directly under this layer. Next, we have an outer core and then the inner core is the deepest major layer of the earth.

The crust and the mantle combine to make up what seems like a solid layer of ground that we walk on but it really is constructed more like a giant puzzle and the pieces slide back and forth a little bit at a time. These pieces are also called tectonic plates by geologists and geophysicists. These sections of our earth are not nicely rounded like real puzzle pieces and sometimes part of the plates get stuck, but the rest of the plate keeps trying to move.

When the movement is finally great enough to cause the part that is stuck to release, there is a tremendous release of energy. This energy produces these explosive ripples known as seismic waves. These waves of energy create the shakes and quakes that we feel in the ground.

The seismographs are the machines that actually record the movements of the earth and can tell scientists how powerful the earthquake was. Surprisingly it seems that many animals have the ability to sense these waves before we are aware of anything amiss. Some animals will exhibit nervous behavior and attempt to hide or leave the area immediately before an earthquake happens. No one knows how they are able to do this, or what it is that alerts them to the event.

The largest earthquake ever recorded in the world was one in Chile in 1960 that measured 9.5 on a scale of 1-10. The largest earthquake in the US was in 1964 in Alaska and the magnitude of that one was 9.2. Today many precautions are taken to keep people and buildings safe when the earth decides to play its own form of bocce ball deep underground.

This is an original news article © The Kids Window

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