Moonquakes are quakes that occur on the moon similar to earthquakes and happen as a result of steady shifting of molten material in the moon's interior. Moonquakes are weaker than earthquakes. There are four known types of moonquakes: deep moonquakes, shallow moonquakes, thermal moonquakes and meteorite moonquakes.
Deep moonquakes can happen up to 700 kilometers below the moon's surface. They occur as a result of tidal stresses sparked by the gravitational tug of war between the moon, the sun and the earth. Shallow moonquakes occur on the moon's surface and can go to depths of between 20 and 30 kilometers. These type of quakes are triggered by landslides of rock in steep crater rims.
Thermal moonquakes are experienced when the freezing crust expands as it goes back into sunlight after days of lunar night time. Meteorite moonquakes occur when a meteoroid crashes into the surface of the moon, causing a rumble.
Moonquakes are less common than earthquakes, and other than shallow moonquakes, they are weaker than earthquakes. According to research conducted by Apollo astronauts, shallow moonquakes can register a magnitude of up to 5.5 on the Richter scale and can last many minutes longer than earthquakes. Similarly sized earthquakes would cause extensive damage to buildings and other structures.