MAN AND NATURAL DISASTERS --- Earthquakes; at that moment she shook in anger.

I want you to imagine taking a stroll with the love of your life, while holding hands. The road is empty and lonely, just the two of you, and the sun has just began to set. You then took your eyes off the road and looked into the eyes that was already staring at you with love. In that split moment, you felt safe, and it seemed as if nothing could ever go wrong. Suddenly, the ground started shaking, shaking so vigorously, it just seems as if the earth have lost its control.

None of you can barely make 2 steps without falling. As if the shaking wasn't enough, the earth were your love stood just sank in, along with the love of your life. Lucky! You were holding his/her hands before that happened. You still clutched to him/her, trying to save him/her, but the weight was too much. Now, you are going down too, you kept on, but your struggle is getting you no where. You just know you can't live without him/her. You are only human, your muscles were tired already, yet the rumbling was still incessant...

Two minutes later, the surface that bore your weight too sank, and it all became dark.

Pixabay.com: Earthquake

This is probably someone's last experience before they lost their life to an earthquake. In this article, I will be telling us what an earthquake is, how it occurs, what causes it and it's effects, and also how to stay alive during an earthquake.

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EARTHQUAKE

Earthquakes are defined as the shaking, rolling or rumbling of the earth's surface. Another name for earthquake is temblors. It normally as a result of two blocks of the earth surface breaking apart from each other due to the tension that results as energy build-up acts on them. It can also be as a result of the slipping of two blocks of the earth past each other.

There are so many forms in earthquakes can come, and it's effect can range from a shock under your feet to being able to destroy a whole city. Don't get it twisted, earthquake doesn't just happen on the land as most people think, it can happen anywhere, be it land or sea.

Normally, whenever an earthquake occurs, it occurs in three stages. The first stage, which is a smaller shock when compared to the rest is called the foreshock. After the foreshock comes the mainshock, which is the one everyone acknowledges as the earthquake itself. The mainshock is finally proceeded by an aftershock which is not as powerful as the mainshock.

It is worth noting that in powerful earthquakes, the foreshock can be so large and powerful that it is mistaken as the mainshock. Foreshocks and aftershock can occur for so many days, weeks and even for months prior or after the occurrence of the main earthquake.

TERMS ASSOCIATED WITH EARTHQUAKES

There are some terms that are associated earthquakes, and for us to fully understand what earthquakes are, we need to get familiarized with these terms.

Seismograph and The Richter Scale (RS):-

There is a device which the scientists use whenever they desire to measure the magnitude of an earthquake, that device is called a seismograph. The Richter Scale itself is just a scale used to compare earthquakes. The magnitude of an earthquake is graded into ten. Thus each number in the Richter scale is 10 times greater than its predecessor and 10 times lower than its successor.

To better understand this, an earthquake that ranks 2 in a Richter scale is 10 times more than the one that ranks 1, and is 10 times less than the one that ranks 3 in the Richter scale. It is a convention though, to regard earthquakes that range from 3-5 in the Richter scale as minor earthquakes, while 5-7 are regarded as moderate earthquakes, 7-8 are major ones, while an earthquake with a Richter number of 8 and above is regarded as a great earthquake and it is always disastrous.

Tectonic plates:-

The tectonic plates are very huge layers that is the constituent of the upper layers of the earth. The tectonic plates are never at rest, they are constantly moving, sliding, stretching and colliding against each other. We on earth don't feel this movement since we move in the same rhythm with it. Each of the tectonic plates is about 80 to 400 kilometres in thickness.

Fault lines or Fault planes:-

Sometimes, weak lines are developed in the tectonic plates. These weak lines are known as fault lines and they occur normally on the earth's surface. There are different types of faults and the major types include the dip-slip, normal, reverse, strike-slip and oblique-slip.

The Hypocenter and the Epicenter:-

The very point below the Earth's surface where the earthquake begins is known as the hypocenter. On the other hand, that point on the Earth's surface which is directly above the hypocenter is called the Epicenter.

Ring of Fire:-

This the region where most of the earthquakes occur. It is found in the coastal belt of the Pacific Ocean. The coastal belt of the Pacific Ocean have been known to experience so much volcanic eruption, and it contains so many fault lines and the tectonic plates movement is more pronounced there. To be more precise, almost 91% of the world's earthquakes and about 81% of the largest earthquakes that have ever occurred in history occurred in this region.

HOW ARE EARTHQUAKES FORMED

To better understand how an earthquake occurs, there is a need for us to know how the earth is arranged. The earth is divided into the crust, the mantle and the core. The core itself which is at the middle is normally very hot (about 5,500°C) therefore, it is liquid in nature, and it also contains iron and nickel.

The mantle is hot too, but not as hot as the core, this, it is a semi molten rock, known as the magma. While the outermost and the hard part of the earth is crust which comprises of both the land we live in and the oceans and ocean deeps. It goes down about 40km derp below the earth's surface. These earthquakes develop at the crust part of the earth.

Just as I said earlier, the internal part of the earth is very hot, and liquid in nature, thus it is not hard to believe that due to the gases present there, there is a pressure build up under the earth surface. This pressure build up is more like an energy, and a small amount of this energy gets to escape from the earth's surface through the actions of volcanoes and through cracks, while most of it is been held in, in the crust.

Picture by Surachit from Wikicommon CC BY-SA 3.0
The Earth crust

The outer crust of the earth appears to be like an arranged jigsaw, thus having rough edges and lines. This energy held within the earth crust is what causes the tectonics plates to slide, glide knock and move about each other. As this energy and pressure continues to build up, it results to a huge tension on this plates, and also a massive pressure on this fault lines.

After some time, this energy built up result to a faults lines formation which also results to the separation of the tectonic plates apart or movement against each other. Since these faults lines are normally covered by earth and vegetation, one might not really notice them, or even know when they spread out the more.

When this movement and separation of the plates happen, there is an earthquake. This energy released escapes out in the form of seismic waves radiating out in all directions, shaking the earth as they move. When this waves finally reaches the earth surface, they result to a violent shake of the ground and everything on it. This violent shaking destroy houses and structures, causes tsunamis and even fire outbreaks and most notably, death.

TYPES OF SHOCK/SEISMIC WAVES

When an earthquake occurs, the shock waves generated moves in x,y,z direction. these three shock waves have distinguishing features and they can only pass through certain layer of the earth. They are:

P-Waves

The P in the name means primary, there features are more like that of sound waves, p-waves are longitudinal waves with short wavelength, high frequency, and they can pass through solid and liquid bodies just like sound. As the ground is compressed and decompressed, the p-wave forces the ground to move forward and backwards. This movement causes the ground to be displaced a bit. This wave can even be reflected and refracted and can even be changed into S-waves in certain situations.

S-Waves

The S-Waves (where "S" stands for secondary) are transverse waves unlike the P-waves. S-Waves are also waves of short wavelength and high frequency, even though they can travel through solids like rocks, moving away in all directions, they cannot travel through liquid. The effects of the S-Wave is quite noticeable, the displacement of walls and fences is done by the S-Wave.

L-Waves

These low frequency waves are created close to the epicenter it was discovered by Alaxander. L-Waves are transverse waves with long wavelength, and it's path of travel is through the outer part of the earth's crust, thus they are referred to as Surface waves. Due to the motion of the low frequency waves that is similar to the water waves as sea, the earth surface rises and falls as it passes through it. This rise and fall movement leads to so much destruction and can pull down buildings, thus the L-waves are regarded as the major cause of destruction during an earthquake.

TYPES OF FAULTS

Based on the movement that occur along fault lines, we have four types of faults. They are, the normal fault, the reverse fault, strike-slip fault, and the oblique fault.

The normal fault:- This type normally occurs were the crust is been pulled apart. When this occurs, the hanging-wall block moves down to a position lower than that of the foot-wall block.

The reverse fault:- Here, the crust is being compressed resulting to the hanging-wall block moving up and positioning itself on top of the footwall block. When this kind of fault occurs on a gently inclined surface, it is referred to as thrust faulting.

Strike-slip Fault:- This fault is said to have occurred when the crustal blocks move past each other at sideways. They normally occur at fault lines that are almost vertical. When this kind of faults movement is such that the dark side moves more to the left, it is called a sinistral strike-slip, but if it's more to the right, it is called dextral strike-slip.

Oblique Slip Fault:- This kind of fault is as a result of any combination of the other three above.

Note:-
Faults lines can be only few metres long, in some other cases, it can be as long as 1000km. The fault ruptures that appears due to an earthquake doesn't necessarily need to be a long straight line, it can be in short offsets.

TYPES OF EARTHQUAKES

Basically we have four different types of earthquakes, I will list them out and also briefly discuss them. They are Tectonics, Volcanic, collapse and explosion earthquake.

Tectonic Earthquakes:-

A tectonics earthquake is the type of earthquake that occurs based on the action of geological forces on adjoining plates and rocks. When this geological forces is applied on these plates, it causes a change on it which can either be physical or chemical. These changes are what results as earth's crust break.

Volcanic Earthquake:-

This type of earthquakes occur far less often than the tectonics earthquakes. The are triggered by the eruption of a volcano. This means that they occur after a volcanic eruption. Since volcanic eruption is a remote occurrences this days, it is not surprising that volcanic eruptions rarely occur.

Collapse earthquake:-

This kind of earthquakes are quite small when compared with the previous two. They occur in mines and underground caverns and are normally as a result of the seismic waves that is generated whenever there is a rock explosion on the earth's surface.

Explosion Earthquake:-

From the name, you can rightfully guess that this type occurs due to human actions like the detonation of bombs, explosion of chemical devices and nuclear plants e.t.c. This kind of earthquake, though quite dangerous, is more easily prevented than the others.

EFFECTS OF EARTHQUAKE

The effects of earthquakes are so much, ranging from the destruction of vegetation and structures to loss of life and prosperity e.t.c. In this section, we will be considering few of these effects.

Ground Shaking:-

Majorly, the cause of destruction during an earthquake is the shaking of the ground which occurs as a result of the passage of the seismic wave. How much of this shaking that is to be felt is dependent on how far the surface of the earth is to the hypocenter, how low the seismic wave will last and the intensity of the earthquake.

Ground Rupture (faulting) which leads to destruction of structures:-

During an earthquake, the ground ruptures along the area the fault zone moves, and any structure that is built across this area will surely collapses, only those structures built adjacent to the fault have chances of surviving the earthquake.

Pixabay.com: A road destroyed by an earthquake

Thus, earthquake always lead to the damage of man-made structure, and if there is anyone inside or close to those structures during the earthquake, they get destroyed by with.

Earthquakes as a trigger for other natural disasters:-

Whenever an earthquake occurs, it causes the ground to shake vigorously. Whenever this shaking occurs, it triggers other disasters avalanches, landslides, rock slide, flooding, tsunami e.t.c. It is quite safe to assume that earthquake most times don't happen alone, but occur along side these other natural disasters they triggered.

Note:-
Tsunamis are most times as a result of an underwater earthquake

Most of these natural disasters, like the landslide and the tsunami, are even more destructive than the earthquake. When an earthquake causes the breaking of pipe, and destruction of dams, or causes a tsunami, it leads to flooding which on its own causes countless deaths and damages.

Fire Outbreak

Fire outbreaks are one of the most common effects associated with earthquakes. When an earthquake occurs, it causes the break of fuel gas and electric lines. When these fuel pipes gets broken due to an earthquake, the fuel, if gas, spreads and all that is required to light it up is just a spark which can be generated by friction. Also, another factor that worsens the situation is that earthquake results to the break of water pipes, and by the time the water will be needed to quench the fire, the water in the reservoir have already leaked out.

Liquefaction of water-laden sediments:-

During an earthquake, the water inside the earth mixes up with the soil and with the sand very close to the surface of the earth forming liquefaction. This forms a soil that is like a quicksand. If a building is directly above this quicksand like soil formed, both the building and the people inside it gets swallowed up. After the earthquake, with time, this soil becomes firm again as the water moves back to a far more deeper position into the ground. Liquefaction occurs majorly at places in which the water level is very close to the earth's surface, and the soil there is a sandy soil.

Economic effects:-

The loss of property associated with earthquake is so much that it takes even decades to replace what was lost. Earthquakes destroy the sources of livelihood of those living in a state, it destroys roads, bridges, dams e.t.c, which will require a huge amount of revenue to repair them.

MAN AND EARTHQUAKES

Earthquakes are very terrible, always occurring in a large scale, and whenever it occurs, it paints history black with the sorrows that accompanies it. Earthquake have happened quite a lot in history, but I will be mentioning only few in this article.

Tangstan Earthquake

The Tangshan earthquake occurred while the people of China slept. It started unexpectedly at exactly 3:42 a.m of July 28, 1976, literally pushing people down from their bed, while at the same time, leveling the city down within seconds. More than 240,000 people died, those 80% that survived had no access to food and water, talkless of electricity.

Even when the relief workers came, they saw no way to enter the city, as the only "motorable" road was destroyed by the earthquake. While the relief workers were still trying to make their way in, an aftershock occurred killing so many more people and also destroying the access to the people completely. The magnitude of this earthquake is 7.8.

Shaanxi Earthquake:-

This earthquake which is probably the world's third deadliest earthquake occurred in Jan 23, 1556. Also known as the Hua County earthquake, this earthquake affected 97 countries, destroying an area of about 520miles in diameter just in China alone. It resulted to the death of about 830,000 people. Everything happened so fast, a witness describing the incident said that the ground suddenly grew up forming hills while some sank immediately forming new valleys. The Richter number of this earthquake is 8.

Hokkaido Earthquake

An earthquake with a magnitude of 8.3 hit Hokkaido, an island in Japan, in the year 1730. It was terrible, even though so much is not known about this earthquake, it really resulted to the a very huge tsunami and landslide, which joined hands with the earthquake to cause havoc in Hokkaido. So many people died, the death toll is about 137,000. Houses, properties and roads were destroyed too by the earthquake.

HOW TO SURVIVE AN EARTHQUAKE

We have seen how terrible and destructive an earthquake can be, but that doesn't mean that it is inescapable. There are few things you can do, which will help you to survive an earthquake. I will be dividing those things into Before, During and After an earthquake.

Before an earthquake

Always keep everything in the house like the mirror, the television, the bookshelves e.t.c, at a firm position so that they might not fall during events like earthquake and get destroyed or even cause damages to someone nearby. Don't set the bed close to the window and make sure that stuffs on top of the room like the chandelier, and the ceiling fans are strongly held in place.

Before time, get everyone in the family to practice, often times, the safety position. This safety position involves how to immediately drop to the ground with your head and neck being covered with the arm. This position is safe, thus preventing being hit in the head by objects falling due to an earthquake. Also study the house for places someone can hide under, and not be in danger of being hit by what he is hiding under.

Always have an emergency kit containing food water and medication always packed, also keep your documents within reach. Before hand, decide with the family members on how to get in touch with one another, if an earthquake occurs.

It is wise to invite a structural engineer, before building or buying your house so as to make sure that your house is not across a fault line.

During an earthquake

Earthquakes always cause the ground to shake, so anywhere you are and an earthquake starts, quickly drop to the ground, and position yourself as thought above so that the earthquake won't push you down, and also, you won't be hit on the head by a heavy object.

If you happen to be on the bed when it started, hide under the bed. But if there is no space, remain on the bed, then, protect your head with a pillow with your back up, facing the ceiling.

If you are driving, most times, it is quite hard to control a car during an earthquake as a result of the ground shaking. Thus, the best thing to do is to stop the car, close all the windows and then stay down, with your head as low as possible. Immediately the ground stop shaking, get away as fast as you can, and also avoid roads and bridges that were affected by the earthquake.

After an Earthquake:-

When the ground stops shaking, look around you and check if the building around you, or you are in is damaged by the earthquake and whether there is a part for you in to escape through. If Yes, get away from that area as fast as possible. If you are trapped, call for help using your cell phone, or tap the wall for help, or even more preferably, blow a whistle.

Once you are out of the building, check for people that were hit due to the earthquake and offer your assistance to them, make sure you do so with caution so that you won't hurt yourself.

Be extremely careful while cleaning up the building. Male sure that you have your noise mask on, and you are wearing a protective clothe. Also put on a thick sole shoe. Also, assume that the earthquake is not over yet, so that your mind will be prepared to quickly drop to the ground invade an aftershock occurs.

Pixabay.com: A house destroyed by an earthquake

CONCLUSION

Earthquakes have really dealt with man. It is the most frequently occurring natural disasters, and the worst part about it is that most times it doesn't just occur alone. As if it's havoc is not enough, it triggers other disasters like the landslides and the tsunami, sometimes both at the same time, releasing their fury too on man. But, we all know that man have always risen above his problems, thus, surely man will discover a way to deal with this problem.

Apart from explosive earthquakes which man can prevent by avoiding anything that will result to nuclear plant and bomb explosions, most earthquakes occur mostly due to natural causes. Since man can't stop them from happening, man can at least predict them. I will conclude by telling us how man can predict earthquake, and thus, escape and avoid being consumed by it.

Animals tend to sense natural disasters before they occur, if we observe animals behaving in a strange manner, we should suspect an earthquake occurrence. Another is if there is an unexplainable sudden increase in the amount of mineral in the underground water, an earthquake is on the way. Sometimes, a sudden increase in temperature, about 10°C to 15°C precedes an earthquake. Also, water levels of wells are known to go down before a major earthquake. Lastly, if you notice Radon gas in well water, be sure that a major earthquake is on its way, as this Radon gas only gets released from rock masses before an earthquake occurs.

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REFERENCES

Types of earthquakes

Types of faults

What is an Earthquake

Types of shock waves

Effect of earthquakes

How to survive an earthquake

Worst disasters in human history

Predicting an Earthquake

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