Earthquakes

An earthquake is the shaking and vibration of the Earth's crust due to movement of the Earth's plates. Earthquakes can happen along any type of plate boundary. Earthquakes occur when tension is released from inside the crust. Plates don’t always move smoothly alongside each other and sometimes get stuck. When this happens pressure builds up. When this pressure is eventually released, an earthquake occurs. Sometimes, there are smaller shocks that occur before which is the foreshock, after which is the aftershock, and main earthquake which is also called the mainshock. Sometimes foreshocks are so big and scientists tell it from a mainshock. Foreshocks and aftershocks can occur for days, weeks, and months of a main earthquake. The size of an earthquake is measured on a Richter scale of magnitude. Each whole number on the Richter scale represents an earthquake 30 times larger than the number below it. Earthquakes that measure less than 3.0 are not usually felt, while one of 5.0 produces the same amount of energy as the Hiroshima atomic bomb. The largest recorded quake happened in Chile in 1960 and measured 9.5. The shock waves traveled around the world for days. A seismograph is an instrument for measuring earthquake (seismic) waves. Seismographs are basically pens suspended over a paper-covered rotating drum. When the earth trembles the pen makes a larger squiggle on the drum, allowing the size of the shaking to be measured if it’s rapid then there is an earthquake and if there is a steady line there is no earthquake