Lunar Seismic Activity

Moonquakes are minuscule compared to earthquakes.

The Apollo missions deployed seismometers and measured the seismic activity on the Moon. The moonquakes observed were very weak, typically below 2 on the Richter scale (the recent earthquake in Japan was Richter scale 9) and the total annual energy released in moonquakes is about 10 million times less than the energy released by earthquakes annually. Most originated deep within the Moon, with only a few coming from near the surface. The seismometers also detected meteoroid impacts and a few intentional crashes of rockets and modules which were used for calibration.

More information at
http://www.lpi.usra.edu/lunar/missions/apollo/apollo_11/experiments/pse/