An earthquake is the sometimes violent shaking of the ground caused by movements of Earth's tectonic plates. Most earthquakes occur along fault lines, which is where two tectonic plates come together.

Earthquakes strike suddenly and violently and can occur at any time, day or night, throughout the year. Smaller earthquakes might crack some windows and shake products off store shelves, but larger earthquakes can cause death and massive destruction, devastating communities and debilitating local economies.

What causes earthquakes?

Earthquakes occur when large sections of the Earths' crust — called tectonic plates — shift. There are seven primary tectonic plates (African, Antarctic, Eurasian, Indo-Australian, North American, Pacific, and South American) and a number of smaller, secondary and tertiary plates. Because of underlying movement in the Earth's mantle, these plates can shift.

This shifting of one plate causes it to rub against or push under or over an adjacent plate. The place where two plates meet is called a fault line, and it's at these fault lines that earthquakes occur.