Earthquake is a sudden shaking of the ground caused by the sudden movement of rock materials on Earth’s surface. It can cause damage to man-made structures such as bridges, roads and buildings and to natural areas such as forests. The severity of this damage depends on how strong the earthquake is and how close to a fault it occurs. It also depends on how well the buildings were designed and built to withstand the shaking.
The most destructive earthquakes occur along tectonic plate boundaries. The plates are giant slabs of rock that make up the Earth’s crust. When the plates collide, slide past each other or become stuck at their edges, friction builds up until the stress becomes too great and the rocks suddenly slip. This release of energy creates seismic waves that can be felt hundreds of miles away.
Scientists record the vibrations on a seismograph and use their location to calculate an estimated intensity for a particular area of the Earth. This information is used to help communities prepare.
There are many warning signs that may lead up to a big earthquake. Unusual animal behavior, small tremors (or foreshocks) and changes in ground water levels such as rising or sinking can signal that strain is building up on fault lines. If you live near the coast, listen for loud ocean roaring which could indicate a tsunami is coming. If you hear it, evacuate to higher ground or inland, avoiding river valleys.