Science Behind The Earthquakes

Science Behind Earthquakes

Tectonic Plates:

Before moving to the Earthquakes, lets first talk about the Tectonic plates. Earth's surface appears to be still, but it is actually a collection of plates that is always moving. Scientists believe that these plates move around due to the currents deep inside the earth. Plates which are present under oceans are much thinner and less dense than those under continents - where they push into each other the oceanic plate gets forced down underneath the continental plate. The outside of earth is broken up into huge slabs called Tectonic Plates. Tectonic Plates are made of Earth's crust together with the top layer of the mantle, called the lithosphere. Over millions of years, these plates move, bump together, overlap, and slide past each other, making new areas of ocean floor, causing earthquakes, creating mountains and volcanoes.

The largest Tectonic Plate is Pacific Plate. It is the only large plate which doesn't carry a continent.

Most Tectonic Plates carry both oceans and continents, only few of them are almost entirely oceanic. Where two plates pull apart under an ocean, new ocean floor is formed. Where plates are pushed together, dramatic landscape can occur. If both edges are continental, a huge mountain range will form in the collision zone. If one plate is oceanic and other continental, the oceanic edge will usually be pushed under its neighbor. Volcanoes occur along the edges of these boundaries, which are called subduction zones. The top layer of Earth is like a jigsaw, with seven or eight large plates and dozens of smaller, more fragmented plates. These plates "float" around, moving on top of the hotter layers below. Their slow, steady movement can change the size of the oceans, and carry continents around the globe.

The edges of Tectonic plates meet up in different ways. The plates move apart, towards each other, or past each other. Earthquakes can occur in any of these circumstances.
55 Millions years ago, the Indian and Asian plates crashed, creating the Himalayas.

Earthquakes:

As we discussed above that, Earth's outer surface is made up of huge slabs called Tectonic plates. As these plates are constantly moving, and push past each other with hard, jerky movements. In some places, the opposing plates become locked together by friction. At that time, there is a gradual build-up of strain in the locked area. Eventually, the pressure becomes so high, that there is a sudden shift between the plates, usually on or near the plate boundary on Earth's surface called Faults. As this time, energy is released in the form of powerful shockwaves, or vibrations. Those vibrations emerges violently through the crust, causing an Earthquakes. Most Earthquakes happen where tectonic plates rub against each other in place called Faults.

What are Shockwaves ?

These are powerful vibrations that spread out from the earthquake focus in all directions. Earthquake produces two types of shock waves, called P and S waves. These waves travel through parts of Earth's interior layers. However, Scientists can work out when a Earthquake happened by detecting these waves as they arrive back at the surface.

Methods For Measuring Earthquakes:

The magnitude of an earthquake is the measure of the energy it releases. Until recently, Scientists used to measure earthquakes with the help of Richter scale, developed by U.S seismologists Charles F. Richter and Beno Gutenberg in the late 1930s.In Richter scale, each number represents an intensity which is ten times greater than the preceding one. No Earthquake has exceeded a value of 9.5, which took place in Chile, South America on May 22, 1960. The Richter scale measure only magnitude of the earthquake. Nowadays, the intensity of an earthquake is measured using the Mercalli Intensity Scale ( named for Giuseppe Mercalli, the Italian scientist who originated it) which uses Roman numerals from I to XII to rate the intensity of earthquakes, according to their effects.
I - II → Hardly felt by human beings, but intensity can be measured by using instruments.
III - IV → Felt indoors as a quick vibration. Hanging objects swing slightly.
V - VI → Rocking motion felt by most people, buildings tremble.
VII - VIII → General alarm, cracks appear in buildings, tree branches break.
IX - XI → Most buildings destroyed, underground pipes torn apart.
XII → Almost every building gets destroyed, rivers change course.