what just happened did we just experience an earthquake but why does this happen and what exactly is an earthquake earthquakes are caused by the release of energy that generate waves which travel in all directions causing the shaking of earth's surface what exactly is this energy what waves what's shaking of earth's surface this is so complicated well calm down let me explain everything in a simple and detailed manner earth is not just one piece it is made up of jigsaw puzzles of around 19 to 20 pieces which are called as tectonic plates these plates are placed on a hot partially molten layer of earth's mantle this is the reason why these pieces are continuously moving they are moving as you are watching this video these plates move around 1 to 10 centimeter each ear but don't worry not all these movements can be felt by us sometimes these movements are extremely strong and can be felt like a lot of vibrations under your feet or it can also destroy an entire city that's called an earthquake the earthquakes occurs in the lithosphere region of the earth an earthquake generates underneath the earth and this releases the energy across the point at which the earthquake occurs under the earth is called hypocenter and the exact place above it at the surface of the earth is called epicenter the most horrifying earthquake recorded till date was of magnitude 9.5 out of 10. this happened in valdevia in southern chile in 1960. another one that happened in japan in tohuku region was of magnitude of 9.0 which happened on march 11 2011. this earthquake caused massive and enormous damage and destruction and took nearly 16 000 people's life with him geologists use a device that can sense the waves created by the movement of the tectonic plates these waves are known as seismic waves and the device is called as seismograph the earthquake events are scaled according to magnitude of the shock and are known as richter scale this magnitude relates to energy released during the earthquake magnitude is expressed in absolute number 0 to 10 where 0 is lowest where people feel nothing and 10 being the highest that can create severe destruction and loss of life over a large in order to know more about earthquake let's jump to the simulator we can see on the screen is the inner core of the earth and then we have outer core mantle and crust the inner core as the name suggests is the innermost layer or the central layer of earth it is like a solid spherical ball in nature with a radius of 1250 kilometers the temperature of earth's core ranges between 4 500 to 5500 degrees celsius facing a pressure of 300 to 360 giga pascals next is outer core it is of about 2200 kilometer thickness and has a temperature similar to inner core that is of 4500 to 5500 degrees celsius then we have the mantle layer which is the semi-solid state of about 2900 kilometer thickness this layer makes around 84 percent of earth's total volume and the last layer is the crust which is like an apple skin when compared to other layers runs from zero to 70 kilometers in thickness which is specifically eight kilometers under sea to 32 kilometers under continents and this is only one percent of the earth's total mass now we can see that there's a grayish white dot let's click on that we can see a small town then we see this in the street view and then when we click on layers view we can see earth's layer the grayish in color is called as crust and the one in reddish color is called as mantle on the left hand corner side we can see we have a small box that says earthquake magnitude on richter scale with three buttons that shows the magnitude of the earthquake if the intensity is between 0 to 2 it can be barely sensed when the intensity is more than 2 and less than 4 we can feel minor vibrations and sense it a little from 4 to 4.9 it is considered as small or a light earthquake range from 5 to 5.9 are considered moderate earthquakes and from the range 6 to 6.9 are considered as strong earthquakes in some time we will see how much damage these magnitudes can do and anything above 7 is considered as major earthquakes which can destroy cities and continents these readings are recorded on a seismograph now let's set the 4 to 4.9 magnitude to see how this earthquake happens we can see the earthquake starts from a point called a hypocenter inside the earth during an earthquake two types of waves are formed one is called body waves and the other are called as surface waves let's see what are called as body waves body waves are the waves that moves through the interior of the earth and through the body of the earth and hence the name when these body waves move these waves come across the surface rocks and generate the surface waves let's see in detail about these body waves and surface waves from this point that is hypocenter waves are released these waves are called primary waves or p waves now what are these p waves p waves are seismic waves that shakes the ground back and forth in the same direction and the opposite direction as the direction of the wave is moving which is similar to the movement of these sound waves this is how a p wave looks like these p waves are the first to be recorded on a seismograph now after a fraction of second when these p waves hit the rocks closer to the surface gives rise to new set of waves the s waves or called as secondary waves these waves are towards the earth crust and these are tremors and vibrations that we feel s waves are the wave motion in a solid medium where the medium moves perpendicular to the direction of the weave after the p wave these s waves are recorded on a seismograph now these s waves hits the surface and starts the earthquake the point at which the earthquake originates on the surface is called an epicenter after the p and s waves comes the surface waves which are the most destructive waves as they cause the movement or the displacement of the rocks which leads to falling of structures and causing harm to life let's once again see the formation of p and s waves we can see that an earthquake of this magnitude that is between 4 to 4.9 causes the damage to nearby small houses but the buildings are okay let's see what happens when the magnitude is between 5 to 5.9 let's reset and then hit the button whoa that's quite some damage the small houses are shattered and the buildings also have cracks we can also see that the road is also cracked now one more thing to notice is that the higher the magnitude the closer the hypocenter is to the epicenter notice this when we move to 6 to 6.9 magnitude the damage is enormous buildings are almost broken roads are cracked and small houses are collapsed earthquakes can really be extremely damaging natural calamity if this is the case when magnitude is limited to 7 imagine how 9 and 9.5 might even look since these are quite commonly occurring magnitudes we have studied them in this simulation it is extremely difficult to predict an earthquake based on a seismograph which is also known as seismometer but even our smartphones can now detect these seismic waves and scientists can use this data to predict earthquake and warn people nasa can use this information in the quake sim software which can use this data to generate more efficient information recent studies showed that before an earthquake nearby regions record very high concentrations of radioactive pair radon and thoron this happens because right before the earthquake these gases are released on the surface from small cracks and if we can detect these gases we can predict a quake at least seven days in advance well here are some tips that can save you in case of an earthquake till then keep yourself safe and see you in the next session well i hope you have enjoyed this session this session is based on an interactive 3d simulation called scholar developed by escobel [Music] visit www.escovell.in to request the download of the software application to try this 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