AN EARTHQUAKE

Defn: an earthquake is the vibration of the earths surface.

Causes of the earthquake
1. Tectonic plates movement. When two plates interact at their boundaries they put forces on each other. These forces of reaction cause physical and chemical changes at their boundaries. Plates move side to side, up and down, and also interact head on. Earthquakes also occur in these areas where new plates are being created and old plates are being sub ducted into the Earth's interior hence an earthquake formation.
2. Volcanic eruption. The molten materials from the mantle erupt with the highest forces hence leads to occurrence of earthquakes.
3. Explosion, the nuclear and chemical devices once take plce may cause an earthquake.

Seismographs are instruments used to record the surface and body waves.