The Science of Earthquakes

An earthquake is an intense shaking of Earth’s surface. The shaking is caused by movements in Earth’s outermost layer.

Simply Earthquakes occur due to the sudden release of energy from the earth's crust. Due to which seismic waves are generated which cause earthquakes.

Scientists can measure the magnitude of earthquakes by measuring these seismic waves on instruments called seismometer.

A seismometer detects seismic waves below the instrument and records them as a series of zig-zags by this means different types of waves intensity can be recorded in the form of graph called ceismograph measured on a scale known as Richter scale.

Why do earthquakes happen

Although the Earth looks like a pretty solid place from the surface, it’s actually extremely active just below the surface. The Earth is made of four basic layers: a solid crust, a hot nearly solid mantle, a liquid outer core and a solid inner core.

These basic layers are made up of their sub layers which combinly makes the structure of the Earth.

The crust and the top of the mantle make up a thin skin on the surface of our planet region called lithosphere.

The lithosphere isn’t a continuous piece that wraps around the whole Earth like an eggshell. 

Earth's outer skin is not a continuous surface. Instead, it is composed of massive segments called tectonic plates. 

Tectonic plates are constantly shifting as they drift around on the viscous, or slowly flowing, mantle layer below.

This non-stop movement causes stress on Earth’s crust. When the stresses get too large, it leads to cracks called faults. When tectonic plates move, it also causes movements at the faults and produced energy which travel in the form of waves known as cesmic waves which cause vibration or shaking of earth in the form of earthquakes.

Simply an earthquake is the sudden movement of Earth’s crust at a fault line.

Center of motion is located in the plate is called Hypo Center.  The center of the earthquake on the earth's surface above it is called the Epicentre.  

An earthquake’s most intense shaking is often felt near the epicenter. However, the vibrations from an earthquake can still be felt and detected hundreds, or even thousands of miles away from the epicenter.

Some time cesmic waves produced due to havey explosion which cause the vibration or shaking of earth as well.

When an earthquake occurs, different types of energy waves are generated.

"P waves" or "primary waves" 

are the first waves to be detected. These are compressional waves that push and pull as they move through rock and fluids.
"S waves" or "secondary waves"
are the next waves to be detected. These waves move only through rock. They move up and down or side to side, perpendicular to the direction in which the wave is moving.

Surface waves

These waves follow P and S waves. They travel along the surface of the earth and thus cause the most damage. 
Surface waves can be characterized as Love waves, which are faster and move the ground from side to side, and Rayleigh waves, which roll like waves on the surface of oceans and lakes.

Two major types of earthquakes

There are two types of earthquakes, earthquakes caused by natural causes are called tectonic earthquakes, while earthquakes caused by human activities are called non-tectonic.  Tectonic earthquakes can also be of extreme magnitude.  Whereas non-tectonics are usually of moderate magnitude.  The effect of the same earthquake can be different on different regions, so there is a lot of destruction in one region, but other regions remain safe.  Earthquake waves travel at a speed of 25,000 kilometers per hour.  In areas of soft soil and sand, they prove to be extremely destructive.  Their magnitude is estimated on the Richter scale from seismograph records.  While the intensity of the visible disaster is measured by the Mercally Intensity Scale.  Earthquakes also occur on the surface of the ocean floor, and the fact is that most earthquakes occur on the ocean floor.  Marine earthquakes or tsunamis create large waves in the sea.  Some of them extend from one hundred miles to 200 miles in length, while their height is up to 40 feet.  When these waves reach the coast, they pass through the coast and enter the land like a flood and spread immense destruction and destruction.

other types of earthquakes

In addition to tectonic earthquakes, seismologists have classified three more earthquake types:

Volcanic: Earthquakes that occur in conjunction with volcanic activity

Collapse: Smaller-scale earthquakes that result from the subterranean collapse of caverns or mines

Explosion: Earthquakes caused by underground explosions of nuclear or chemical devices.

Induced seismicity: is typically earthquakes and tremors that are caused by human activity that alters the stresses and strains on Earth's crust.

Fracking:  is an informal term for hydraulic fracturing, a process used to increase the flow of oil or gas to a production well.

Seismic events associated with fracking  may cause earthquakes.

Artificial Manmade: Scientists have known for a long time that humans can cause earthquakes, especially when we mess around with underground faults. 

And by producing artificial waves in earth crust Haarp is the best example ot it now these days.

Earthquake Foreshocks 

Sometimes an earthquake has foreshocks. These are smaller earthquakes that happen in the same place as the larger earthquake that follows. Scientists can’t tell that an earthquake is a foreshock until the larger earthquake happens. The largest, main earthquake is called the mainshock. Mainshocks always have aftershocks that follow. These are smaller earthquakes that occur afterwards in the same place as the mainshock. Depending on the size of the mainshock, aftershocks can continue for weeks, months, and even years after the mainshock!

Earthquakes regions

The main reasons of earthquakes in these regions are mainly tectonic earthquakes

The regions of the world where earthquakes occur more are mainly located in 3 belt belts.  The first belt, which is connected to the Himalayan mountains towards the east, passes through the Himalayan mountains in the northern regions of India and Pakistan, passes through Afghanistan, Iran and then Turkey to continental Europe and from Yugoslavia to France, i.e. to the Alps.

The second belt starts from the mountain range of Alaska on the western edge of the continent of North America and includes the Rocky mountains towards the south, passes through Mexico and reaches Chile through the countries of Colombia, Ecuador and Peru located in the western part of the continent of South America.  Is.  While the third belt starts from Japan in the east of the continent of Asia, passes through Taiwan and reaches the islands of the Philippines, Brunei, Malaysia and Indonesia in the south.  50 percent of earthquakes in the world originate in the Himalayas, Rocky Mountains and Andes mountains and these three mountain ranges are located in the belts mentioned above.  About 40 percent of earthquakes occur in the coastal areas of continents and their vicinity, while the remaining 10 percent of earthquakes occur in areas of the world that are neither mountainous nor coastal.

Inspite of the scitific belives some other belives including religious belives are alwse present about earthquakes discuss in detail in the article religious belives about earthquakes.

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Historical review of destrcutive Earthquakes

When and where the oldest earthquake occurred in history cannot be said with certainty, but the first earthquake recorded by man in history occurred in China in 1177 BC, about three thousand years ago.  After that, the oldest records are found in Europe in 580 BC and Sparta in Greece in 464 BC.  Historians believe that this earthquake occurred during the Polynesian War fought between Sparta and Athens.

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