A number of online resources (NASA & https://astronomy.com/news/2019/06/what-did-the-apollo-astronauts-leave-behind) state the reason for decommissioning the Apollo ALSEPs on September 30, 1977 was due to lack of funding resulting from budget cuts.
Apparently the ALSEPS received 153,000 commands while operational.
Although the experiments were turned off, the transmitters continued to send carrier signals which were used by various institutions, including the Jet Propulsion Laboratory, for geodetic and astrometric studies, and spacecraft navigation.
After four years of sending a steady flow of data, the Apollo 14 ALSEP developed an intermittent fault. It began an intermittent ‘on’ and ‘off’ cycle for its last two years, due to a short circuit in one of the power conditioning units. It seemed related to the temperature of the unit, reacting to the position of the Sun over the site.
The ALSEP program cost NASA an estimated \$US200 million, including the design and development of the stations and experiments, support engineering work in Houston, and the analysis of the data by dozens of University laboratories around the world. It cost NASA \$US2 million a year to operate.
Due to other budgetary issues some of the data from the ALSEPs was lost when the recording tapes were wiped, so they could be used for other projects.
“Before (March 1976) NASA wanted us to read the data, extract what we want and send it back to NASA for archiving,” said Nakamura. “Then somebody in a committee said there’s no use keeping those.”
Magnetic tape reels were expensive and bulky. Under pressure to supply other projects and control cost, NASA, like many others at the time, wiped and reused tapes. The unfortunate reality is that data recorded during the first five years of the Apollo program, before NASA began keeping ARCSAV tapes, is likely lost forever.
Not from the most authoritative source, some facts about Moon quakes.
There are four separate kinds of moonquakes, 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 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.
While deep moonquakes are generally only magnitude 2 or smaller, they occur on a monthly basis, whereas quakes occurring along the same fault line on Earth may be decades or centuries apart.
Moonquakes also last longer than earthquakes, which typically cease within a few minutes.
Since the moon is much drier and cooler than Earth, the vibrations carry for longer, whereas Earth’s more compressible structure acts like a sponge to absorb vibrations.
