Earthquake

Since the formation of the world, it has been known that earthquakes have occurred sequentially in seismically active areas and millions of people and shelters have been destroyed as a result.

   As it is known, our country is located one of the most effective earthquake zones in the world. It is a fact that, as there were many destructive earthquakes in our country in the past, we will suffer a great loss of life and property with earthquakes that will occur frequently in the future.

Earthquake Zones

   According to the Earthquake Zones Map, it is known that 92% of our country is in earthquake zones, 95% of our population lives under earthquake danger, and also 98% of large industrial centers and 93% of our dams are located in earthquake zones.

   In the last 58 years, 58,202 citizens lost their lives, 122,096 people were injured and approximately 411,465 buildings were destroyed or severely damaged due to earthquakes. As a result, it can be said that an average of 1.003 citizens die each year from earthquakes and 7,094 buildings are demolished.

What Is Earthquake?

   The phenomenon of the vibrations that occur suddenly due to the ruptures in the earth’s crust is called “EARTHQUAKE”, spreading in waves and shaking the environment and the earth.

   The earthquake is a natural phenomenon that shows that the earth that people regard as immobile and safely stepped on will also play and that all the structures on it can be damaged and destroyed in a way that causes loss of life.

   “Seismology” is the branch of science that examines how an earthquake occurs, how earthquake waves propagate in the earth, measurement instruments and methods, evaluation of records and other issues related to earthquakes.

Causes and Types of Earthquake:

   There is an earth model supported by the data obtained from geological and geophysical studies on the internal structure of the earth. According to this model, there is a lithosphere formed in the outer part of the earth, approximately 70-100 km thick. Continents and oceans are located in this stone sphere. The belt between the lithosphere and the core, with a thickness of 2,900 km, is called the Mantle. It is accepted that the core under the mantle consists of a mixture of Nickel-Iron. It is known that the temperature of the ground increases as the surface is deepened. From the fact that transverse earthquake waves cannot propagate in the core of the earth, it is concluded that the core must be a liquid medium.

   Although the mantle is generally solid, it contains local liquid environments as it goes deep from the surface.

   Under the Stonesphere, there is a soft Upper Mantle called as Astenosphere. Forces formed here, especially due to convection currents, the stone crust is broken up and divided into many “Plates“. Convection currents formed in the Upper Mantle are attributed to the high temperature caused by radioactivity. As the convection currents rise upwards, they cause stresses in the stone and then the formation of plates by breaking the weak zones. There are currently as many as 10 large plates and many smaller plates. Together with the continents resting on these plates, they float like a raft on the Astenosphere and move at a speed that humans cannot feel relative to each other.

   Where convection currents rise, the plates move away from each other and form the mid-ocean ridges in the hot magma that emerges from here. Friction and compression occur in the areas where the plates touch each other, one of the friction plates sinks down into the Mantle and melts and forms the wear zones. This sequential event caused by convection currents continues under the background.

   The boundaries of these plates, where the plates that make up the earth’s crust rub against each other, compress each other, overlap or enter under each other, appear as places where earthquakes occur in the world. The vast majority of earthquakes in the world occur on narrow belts at the plate boundaries where these plates force each other.

   Above, we said that the “Plates” forming the earth’s crust are in motion due to the convection currents in the Asthenosphere and therefore they repel each other or open from each other and the earthquake zones formed by these events where these events take place.

   There is a frictional force between the two plates pushing each other or getting under the other, which prevents movement. In order for a plate to move, this frictional force must be eliminated.

   A movement occurs when the frictional force is exceeded between a plate being pushed and another plate. This movement takes place in a very short unit of time and is shocking. Eventually, earthquake (shaking) waves emerge that can spread very far, these waves spread by shaking the environments they pass through and decreasing their energy as they move away from the direction of the earthquake. Meanwhile, land fractures, sometimes visible, extending for kilometers and called fault, may occur on the earth. These fractures sometimes cannot be observed on earth, they may be hidden by surface layers. Sometimes, a fault that originated from an old earthquake and reached the ground, but was covered over time, can play again.

   The explanation of the occurrence of earthquakes in this way and under the name of “Elastic Back-Tab Theory” was made by the American Reid in 1911 and has been proved by being tested in laboratories.

   According to this theory, when the energy stored elastically by the unit deformation accumulation formed gradually at any point, depending on time, reaches a critical value, it overcomes the friction force existing along the fault plane and creates the relative movements of the rock blocks on both sides of the fault line. This event is a sudden displacement movement. These sudden displacements are caused by the release and discharge of the unit deformation energy accumulated at one point, in other words, by the transformation into mechanical energy and consequently by the breaking and tearing movement of the ground layers.

   In fact, it is impossible for rocks to break without a unit of displacement accumulation beforehand. This unit creates displacement movements, convection currents formed in the upper mantle in the earth’s crust, which appears to be motionless, the rocks can resist until a certain deformation and then break. Earthquakes occur as a result of these ruptures. After this event, some or all of the stresses and energy accumulated since far from the rocks are removed.

   Elastic back tabs (throws) occur mostly on both sides of the fault and in the opposite direction in faults that occur during this earthquake event.

   Faults are usually named according to their direction of movement. Faults that occur mostly as a result of horizontal movement. It can also be mentioned that the two separate blocks formed by the fault move to the right or left relative to each other, which are examples of right or left directional strike-slip fault.

   Faults that occur with vertical movements. Most faults can have both horizontal and vertical movement.

Earthquake Types

   Earthquakes can be of different types according to their causes. Although most of the earthquakes in the world occur as described above, there are some other types of earthquakes that occur due to other natural reasons. Earthquakes resulting from the movement of the plates described above are generally referred to as “tectonic” earthquakes and these earthquakes mostly occur at the boundaries of the plates. 90% of the earthquakes on the earth fall into this group. The earthquakes in Turkey are also mostly tectonic earthquakes. The second type of earthquakes are “volcanic” earthquakes. These are formed as a result of the eruption of volcanoes. It is known that such earthquakes occur with the explosions caused by the gases formed as a result of the physical and chemical events during the emergence of the molten material in the depths of the earth. These are also local as they are related to volcanoes and do not cause significant damage. Some of the earthquakes in Japan and Italy are included in this group. because there are not this type of active volcanoes, earthquakes in Turkey.

   Another type of earthquakes are “collapse” earthquakes. These cavities underground (caves), galleries in coal mines, and cavities formed as a result of melting in salt and gypsum land are formed by the collapse of the ceiling block. Their sensation areas are local and their energy is low, they do not cause much damage. It is known that large landslides and meteorites falling from the sky also cause minor tremors

   After the Deep Sea Earthquakes, the focus of which is at the bottom of the sea, waves occur in the seas to the shores and sometimes cause great damage to the coasts, which are called (Tsunami). In Japan, where sea earthquakes were common, 30,000 people died from the Tsunami in 1896.

How do We Prevent From The Earthquake?

   When an earthquake occurs, everyone must protect themselves. First of all, try to be calm during an earthquake. If you are in a closed area, take shelter away from windows and items that could fall on you or spill. If you are outside, stay away from buildings and electricity poles. If you are on the road, stay away from underground passages and do not approach bridges. And the most important thing; protect your head and neck. Bend over, grab and hold.

• If You Are at Home at Earthquake:

Just bend over, close, and grab a sturdy table or furniture away from windows and windows. Especially lean or lie on the side of sturdy items such as the side of the sofa, protect and hold your head and neck by closing as we have seen before. In the living room, bookshelves and books may fall on you. The stereo and TV may fall. If you sleep on your bed during the earthquake, get down to the bed right away, bend over, shut down, and hold onto a firm place. Turn off appliances such as stoves, radiators, stoves and televisions after the earthquake. If you cannot close it, remind the elders of the family.

• If You Are at School Durıng Earthquake

Just bend over to or between the rows, grab and hold. Protect your head and neck with your hands or something you find soft. Keep your face away from windows and windows.

• During Earthquake If You Are in The Corridor

If there is no table or desk near you, bend over to a wall and shut.

• If You Are in The Library During Earthquake

Bend, grab and hold where books won’t fall on you and away from windows. Create your school and classroom earthquake plan with your friends and teachers. Discuss this plan in practice. Listen to your teacher about what to do after the earthquake is over.

• During Earthquake If You’re Outdoors

Try to move towards an empty spot away from windows, buildings, electrical wires. If you can’t go, bend down away from buildings, cover and protect your head and neck. Get away from playground equipment such as slides, seesaws and swings in the playground.

• During Earthquake If You’re in Car:

To the driver; Tell him to stay away from posts, overpasses and bridges and do not leave the car. Keep calm, don’t panic. Doing so will help calm the people around you.

• During Earthquake If You Are in Theater / Cinema:

Calm down. Wait for the announcements of the authorities. Do not run to the doors. Bend between rows, cover to protect your head, hold if there is a suitable place. If there is something to fall on us (like a chandelier hanging from the ceiling) move somewhere else.

• During Earthquake If You Are in Shopping Malls

Don’t panic. Avoid large columns, shelves, and cabinets. Do not run to fire exits, stairs and escalators and elevators. Listen to the announcements, follow the warnings of the store security personnel. Drop off your purchased items. Lean over the counter sides, close and hold.

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