Lunar seismology
Lunar seismology is the study of ground motions of the Moon and the events, typically impacts or moonquakes, that excite them. History Several seismographic measuring systems have already been installed on the Moon and their data made available to scientists (such as those from the Apollo Lunar Surface Experiments Package). The existence of moonquakes was an unexpected discovery from seismometers placed on the Moon by Apollo astronauts from 1969 through 1972. The Apollo 11 instrument functioned through August of the landing year. The instruments placed by the Apollo 12, 14, 15, and 16 missions were functional until they were switched off in 1977. Moonquakes are not believed to be caused by tectonic plate movement (as earthquakes are), but by tidal forces between Earth and the Moon. Further data is needed to clarify the origins and effects of the forces causing moonquakes. Major findings Moonquakes Several categories of moonquakes were recorded. Hundreds of deep moonquakes were recorded along with 28 shallow events. The deeper quakes are caused by tidal forces with the Earth and tended to occur in clusters. The shallow events have tectonic origins. Although more rare than deep events, the shallow events were larger, with body wave magnitudes >