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| Earthquake |
What is Earthquake:
In simple word, An earthquake is what happens when two blocks of the earth quickly slide past one another. The surface where they slide is known the fault or fault plane. The area below the earth’s surface where the earthquake initiated is known the hypocenter, and the area directly above it on the surface of the earth is called the epicenter.
Many times an earthquake has foreshocks. These are little earthquakes which occurs in the similar place as the bigger earthquake that follows. Researchers cannot inform that an earthquake is a foreshock until the bigger earthquake happens. The biggest, major earthquake is known as the mainshock.
Mainshocks always have aftershocks that follow. These are Little earthquakes that happens afterwards in the similar place as the mainshock. According to the size of the mainshock, aftershocks can regularly for weeks, months, and even years after the mainshock.
What causes earthquakes and where do they happen?
The earth has 4 main layers:
1) the inner core, 2) outer core, 3) Mantle and 4) crust.
The crust and the upper of the mantle make up a thin skin on the surface of our planet. But this skin is not overall in one piece. It is prepared from of several pieces like a puzzle covering the surface of the earth. Not only that, but these puzzle pieces keep slowly moving around, sliding past one another and bumping into each other. We say these puzzle pieces tectonic plates, and the edges of the plates are known the plate boundaries.
The plate boundaries are prepared from several faults, and most of the earthquakes surround the world happen on these faults. Since the edges of the plates are rough, they get stuck while the rest of the plate keeps moving. At last, when the plate has carried far enough, the edges unstick on one of the faults and there is an earthquake.
Why does the earth shake when there is an earthquake?
While the edges of faults are stuck together, and the rest of the block is moving, the energy that would usually cause the blocks to slip past one another is being stored up. When the force of the moving blocks lastly overcomes the friction of the jagged edges of the fault and it unsticks, whole that stored up energy is released.
The energy emitted outward from the fault in all directions in the form of seismic waves like ripples on a pond. The seismic waves shake the earth as they move through it, and when the waves reach the earth’s surface, they shake the ground and anything on it.
How are earthquakes recorded?
Earthquakes are noted by apparatus or instrument known as seismographs. The recording they make is called a seismogram. The seismograph has a base that sets stably in the ground, and a large weight that hangs free.
When an earthquake occurs the ground to shake, the base of the seismograph shakes too, but the hanging weight does not. Instead the spring or string that it is hanging from absorbs overall the movement. The distinguishable in position between the shaking part of the seismograph and the motionless division is what is noted.
How do scientists measure the size of earthquakes?
The size of an earthquake based on the size of the fault and the amount of slide on the fault, but that’s not something researchers can easily measure with a measuring tape since faults are few kilometers deep beneath the earth’s surface. They use the seismogram recordings prepared on the seismographs at the surface of the earth to calculate how big the earthquake was.
A little wiggly line that doesn’t wiggle very much means a little earthquake, and a long wiggly line that wiggles a lot means a big earthquake. The length of the wiggle based on the size of the fault, and the size of the wiggle based on the amount of slide.
The size of the earthquake is known its magnitude. Every earthquake have one magnitude. Researchers already tells about the intensity of shaking from an earthquake, and this moves based on where we are during the earthquake.
How can scientists tell where the earthquake happened?
Seismograms come in handy for placing earthquakes too, and being able to look the P wave and the S wave is important. We learned how P & S waves each shake the ground in various ways as they travel through it. P waves are also quicker than S waves, and this situation is what allows us to inform where an earthquake was.
To understand how this works, let’s compare P and S waves to lightning and thunder. Light travels quicker than sound, so during a thunderstorm we will first look the lightning and then we will hear the thunder. If we are near to the lightning, the thunder will boom right after the lightning, but when we are far away from the lightning, we can measure few seconds before we hear the thunder. The further we are from the storm, the longer it will take between the lightning and the thunder.
P waves are like the lightning, and S waves are like the thunder. The P waves moves quickly and shake the ground where we are first. Then the S waves follow and shake the ground also. If we are near to the earthquake, the P and S wave will come one right after the other, but if we are far away, there will be more time between the two. By looking at the amount of time between the P and S wave on a seismogram noted on a seismograph, researchers can inform how far away the earthquake was from that place.
However, they can’t inform in what direction from the seismograph the earthquake was, only how far away it was. If they draw a circle on a map around the station where the radius of the circle is the measures distance to the earthquake, they know the earthquake lies somewhere on the circle.
Scientists afterthat use a technique known triangulation to actually where the earthquake was. It is known triangulation because a triangle has three sides, and it takes three seismographs to placed an earthquake. If we draw a circle on a map around three various seismographs where the radius of each is the distance from that station to the earthquake, the intersection of those three circles is the epicenter.
So, this are the earthquake causes and Effects and instrument used for earthquake recording.