Table of ContentsWhat is an earthquake?What causes earthquakes and where do they occur?Why does the earth shake her when there is an earthquake?How are earthquakes recorded?How do scientists measure the size of earthquakes? How can scientists know where the earthquake occurred? Can scientists predict earthquakes? What is an earthquake? An earthquake is what happens when two blocks of earth suddenly slide past each other. The surface on which they slide is called a fault or fault plane. The place below the earth's surface where the earthquake begins is called the hypocenter, and the place directly above it on the earth's surface is called the epicenter. Say no to plagiarism. Get a tailor-made essay on “Why Violent Video Games Should Not Be Banned”? Get the original essay Sometimes an earthquake causes shaking. These are smaller earthquakes that occur in the same location as the larger earthquake that follows. Scientists cannot say that an earthquake is a shock until a larger earthquake occurs. The largest main earthquake is called a mainshock. Main shocks always have aftershocks that follow. These are smaller earthquakes that then occur in the same location as the mainshock. Depending on the magnitude of the mainshock, aftershocks can continue for weeks, months, or even years after the mainshock! What causes earthquakes and where do they occur? The Earth is made up of four main layers: the inner core, the outer core, the mantle and the crust. The crust and the top of the mantle constitute a thin skin on the surface of our planet. But this skin is not in one piece: it is made up of many pieces, like a puzzle covering the surface of the earth. Not only that, but these puzzle pieces continue to move slowly, sliding over each other and colliding. We call these puzzle pieces tectonic plates, and the edges of the plates are called plate boundaries. Plate boundaries are made up of many faults, and most of the world's earthquakes occur on these faults. Because the edges of the plates are rough, they get stuck while the rest of the plate continues to move. Finally, when the plate has moved far enough away, the edges come off on one of the faults and there is an earthquake. Why does the earth shake when there is an earthquake? As the edges of the faults are stuck together, and the rest of the block is moving, the energy that would normally cause the blocks to slide past each other is stored. When the force of the moving blocks finally overcomes the friction of the jagged edges of the fault and they break away, all the stored energy is released. The energy radiates outward from the fault in all directions in the form of seismic waves like the ripples of a pond. Seismic waves shake the earth as they pass through it, and when the waves reach the earth's surface, they shake the ground and everything on it, like us and our homes! (see P&S Wave box)How are earthquakes recorded?Earthquakes are recorded by instruments called seismographs. The recording they make is called a seismogram. The seismograph has a base firmly anchored in the ground and a heavy weight that hangs freely. When an earthquake.