Earthquake is an abrupt release of energy that shakes the Earth’s surface. It can cause widespread damage to buildings and other man-made structures, especially if they were not designed or built to withstand seismic activity. Earthquakes also generate tsunamis, which can affect coastlines globally. They can also trigger mud slides, fires and floods that compound the loss of life and property.
Earthquakes are generally caused by the movement of the Earth’s Tectonic plates. They cover the Earth like a watermelon rind or orange peel covers a fruit, but instead of smooth edges, they have rough edges that keep moving around each other (Figure 4).
The edge of one plate can get stuck on another, and when the friction becomes too much, the plates slip past each other. This sudden slip releases energy in the form of seismic waves that travel outward from the fault.
Scientists use seismograms to record the earthquake. The way the wiggly lines on a seismogram change in length tells them how big the earthquake was. They can also determine the direction of the earthquake by looking at the time difference between P and S waves recorded at several stations.
An earthquake’s magnitude tells us how much energy it has released. Magnitude is measured on the Richter scale, with 1 being a very light quake and 8 being a very large quake. The earthquake’s shaking intensity is also measured and rated on the same scale. The energy of an earthquake can vary over a wide area, depending on its depth and type of material.
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