Research Apollo Data.

Nasa said its colleagues plan to continue to study the Apollo data, but they say they need more data. That could be collected by more instruments over a wider area of the moon.
This is needed to test their transformational faulting hypothesis. Frohlich and Nakamura are also hoping NASA will return to the moon and install a few dozen seismic stations. “Right now, we know virtually nothing about the moon’s interior,” Frohlich says. “So we have to make a lot of assumptions about the moon’s internal composition, which means all our theories are pretty sketchy. Sometimes so much speculation is fun, but more often, as in the case with deep moon-quakes, it’s just frustrating.” Between 1969 and 1972, five Apollo missions installed seismic stations at their landing sites on the nearside of the moon. Because the moon was thought to be seismically dead, the instruments were left almost as an afterthought to detect meteor strikes. But from the time the stations were switched on until they were decommissioned in 1977, they recorded hundreds of internally generated moon-quakes, some as strong as magnitude 5.5 on the Richter scale.

For 40 years, scientists have scoured the Apollo seismic data for an explanation of these moon-quakes. Because the moon lacks active plate tectonics, moon-quakes must be driven by different forces than most quakes on Earth. 
Extreme temperature changes may account for the less common shallow moon-quakes, but a good explanation for deep moon-quakes remains elusive. Now, a new study crosses one long-standing theory about what triggers deep moon-quakes off the list. Instead, the study suggests, moon-quakes might have more in common with earthquakes than previously thought. The Apollo Lunar Surface Experiments Package (ALSEP) comprised a set of scientific instruments placed by the astronauts at the landing site of each of the five Apollo missions to land on the Moon following Apollo 11 landing. This image shows the Apollo 16 package. ALSEP was a collection of geophysical instruments designed to continue to monitor the environment of each Apollo landing site for a period of at least a year after the astronauts had departed. Designed for a life of one year (Apollo 17 The mystery of the moon-quakes deepens. As analysis of Apollo data reveals over 200 tremors on the lunar surface. Researchers say there are four distinct types of quake. Some are as deep as 700km under the surface As this discovery made from seismic data from Apollo 16 mission in 1972. Researchers have uncovered over 200 previously unknown tremors on the moon by analysing data from the Apollo missions. The find gives new insight into the moon's geology, and reveals four distinct types of quake hit the orbiting body.  The algorithm-based program uncovered 210 previously unknown tremors and scientists at Max Planck Institute for Solar System Research say additional new discoveries will follow. The software uncovered 210 previously unknown tremors, and gives new insight into the moon's geology.

There are four separate kinds of moon-quakes, registering as shadowy echoes on the Apollo mission seismometers. The first type is deep, occurring about 700 km below the surface, and believed to be caused by tides and linked to its orbit around the earth. A second type, the result of a meteorite crashing into the surface, takes the form of vibrations. The third type is a thermal in nature; after two weeks of lunar night (and deep-freeze temperatures), the morning sun causes an expansion, and ultimately cracking, of the moon's frigid crust. Finally, the fourth type is a shallow quake occurring 20 or 30 kilometres (about 12 to 19 miles) below the surface. 'The system is trained to recognize deep moon-quakes, impacts, and shallow moon-quakes, and performs reliably,' wrote the authors. Apollo 11, the first spacecraft to land on the moon, planted not only an American flag on the mysterious lunar surface but also seismographic equipment. 

Since that historic first landing in 1969, Apollo astronauts from four additional missions have placed seismometer stations on the lunar surface through 1972, Earth Magazine explains. Until the hour they were decommissioned in 1977, these stations radioed seismic data from the moon back to Earth.
 Analysing the data in the years since, scientists have identified about 13,000 separate tremors, some registering a 5.5 on the Richter scale - a magnitude strong enough to cause slight damage to buildings. 'The algorithm's demonstrated ability to detect rare events and flag previously undefined signal classes as new event types is of particular interest,' wrote the authors.  Moon-quakes have been the only confirmed events recorded on any extra-terrestrial body so far, the researchers noted in their new study. Importantly, lunar tremors look different from the seismic activity seen on Earth, according to NASA Science, and they arise from a different source. At least one research team wondered, Could there be additional lunar activity not yet discovered in the Apollo seismic data? To answer this question, Dr. Brigitte Knapmeyer-Endrun and her team developed a unique algorithm similar to those used in speech recognition programs. After information from one moon tremor is fed into the new algorithm-based program, it is able to search new data and recognize similar patterns. Running the program on a small subset of data from 1972, the researchers classified more than 50 percent of previously uncategorised events and discovered more than 200 new events not listed in the current lunar event catalogue. The researchers said their new program could identify additional undiscovered events in the existing data and may be useful in 'future seismometer missions to other planets,' including NASA's forthcoming Insight mission to Mars. There are four separate kinds of moon-quake, registering as shadowy echoes on the Apollo mission seismometers. The first type is deep, occurring about 700 km below the surface, and believed to be caused by tides and linked to its orbit around the earth. A second type, the result of a meteorite crashing into the surface, takes the form of vibrations. was for two), they ended up working for up to 8 years, the experiments permanently shut down by Mission Control on 30 September 1977.

The third type is thermal in nature; after two weeks of lunar night (and deep-freeze temperatures), the morning sun causes an expansion, and ultimately cracking, of the moon's frigid crust.
Finally, the fourth type is a shallow quake occurring 20 or 30 kilometers (about 12 to 19 miles) below the surface.The first three kinds of tremors are considered mild, only the fourth kind is able to register in the 5.5 range on the Richter scale. The exact origin of the fourth type of quake remains unclear. According to NASA Science, the Apollo seismometers were all placed on one side of the moon in a relatively small region so the exact GPS is difficult to pinpoint. Importantly, the moon is unlike the earth in that it lacks active plate tectonics. The earth's outer crust is broken up into thick plates that move on top of a soft, underlying mantle. The plates move both horizontally and vertically and such motions can cause earthquakes. Because the moon lacks this same feature, scientists say the shallow moon-quakes are caused by different forces unseen on earth. Because water has yet to be discovered on the moon, its been a suggestion mineral phase changes may make certain areas of the moon weaker, resulting in moon-quakes triggered by tidal pressure. “This is one of the first broader viewpoints I've seen,” says Yosio Nakamura, also of the University of Texas at Austin. “Other studies have failed to find a clear relationship between tides and moon-quakes, but this is the first to suggest an alternate mechanism.” Although many think its time to move on just beyond safety to a colony that has water and can support life.