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EXPLANATION OF THE GOVERNOR OF ISTANBUL ALI YERLIKAYA:
According to data from AFAD; At 2:51 p.m., there was a 6.6 magnitude earthquake with the epicenter of the Aegean Sea: Seferihisar. No negativity was reported regarding the earthquake that was felt in Istanbul.
WHAT IS EARTHQUAKE?
“EARTHQUAKE” is the event in which vibrations that occur suddenly due to ruptures of the earth’s crust propagate in waves and shake the environment and the earth’s surface.
The earthquake is a natural phenomenon that shows that the land that people consider immobile and safely trodden will also play and that all structures on it can be damaged and destroyed in a way that results in loss of life.
“SEISMOLOGY” is the branch of science that examines how earthquakes occur, how seismic waves propagate within the earth, measurement tools and methods, log evaluation, and other issues related to earthquakes.
CAUSES AND TYPES OF EARTHQUAKE
There is a terrestrial model supported by data obtained from geological and geophysical studies on the internal structure of the earth. According to this model, there is a stone sphere (lithosphere) formed on the outside of the earth, approximately 70-100 km thick. The continents and oceans are located in this stone sphere, the belt between the lithosphere and the core, which is 2,900 km thick, is called the Mantle.
The core under the mantle is accepted to consist of a Nickel-Iron mixture. Soil temperature is known to increase as the surface deepens. From the fact that transverse seismic waves cannot propagate in the core of the earth, it follows that the core must be a liquid medium. Although the mantle is generally solid, it contains local liquid environments as it penetrates the surface.
Beneath Taşküre, there is a soft upper mantle called the Asthenosphere. The forces formed here, especially due to convection currents, the stone crust is fragmented and divided into many “plates”. The convection currents formed in the Upper Mantle are attributed to the high temperature caused by radioactivity. As the convection currents rise, they cause stresses in the stone and then the formation of plates by breaking up weak areas. There are currently up to 10 large plates and many smaller plates. Together with the continents that rest on these plates, they float like a raft in the Asthenosphere and move at a speed that humans cannot sense each other.
Where convection currents rise, plates move away from each other and form ocean ridges in the hot magma emerging from here. Friction and compression occur in the areas where the plates touch each other, one of the friction plates sinks into the mantle and melts and forms the wear zones. This sequential event caused by convection currents continues in the background.
The boundaries of these plates, where the plates that make up the Earth’s crust rub against each other, compress, overlap, or fall, appear as places where earthquakes occur in the world. The vast majority of earthquakes in the world occur in narrow belts at plate boundaries where these plates force each other.
Previously, we said that the “Plates” that form the earth’s crust are in motion due to convection currents in the Asthenosphere and therefore repel or open each other and the areas where these events take place form the seismic zones.
There is a friction force between the two plates that are pushed or placed under the other, preventing movement. For a plate to move, this frictional force must be removed.
A movement occurs when the frictional force between a plate being pushed and another plate is exceeded. This movement takes place in a very short unit of time and is shocking. Eventually, earthquake waves (jolts) arise that can spread very far, these waves propagate shaking the environments they pass through and decreasing their energy as they move away from the direction of the earthquake. Meanwhile, sometimes visible land fractures that stretch for miles and are called FAYs can occur on land. These fractures sometimes cannot be observed in the ground, they can be hidden by superficial layers. Sometimes a fault that originated from an ancient earthquake and reached the surface but was covered over over time can reproduce again.
The description of the occurrence of earthquakes in this way and under the name “Theory of the elastic spring” was made by the American Reid in 1911 and has been proven by tests in laboratories.
According to this theory, when the elastically stored energy by the accumulation of strain gradually formed at any point, depending on time, reaches a critical value, it exceeds 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 scroll movement. These sudden displacements are produced by the release and discharge of the accumulated strain energy at a point, that is, by the transformation into mechanical energy and consequently by the breaking and tearing movement of the soil layers.
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