Despite having very little geological activity, without any active tectonic plates, the moon is prone to shaking shifts.

As far as I know, moonquakes can be caused by the Sun, thermal quakes, or by meteorites but moonquakes of up to 5.5 in the Richter scale, lasting 10 minutes, have been reported. I doubt either the Sun or a meteorite could cause them. In the first case, thermal quakes would have a low magnitude and, in the case of meteorites, the moonquake wouldn't last 10 minutes.

Why do these long and high magnitude occur and what causes them?

  • 2
    $\begingroup$ Going to be picky and point out that there is no geological activity and not much selenological activity either $\endgroup$
    – Alchymist
    Aug 4 '15 at 14:44
  • $\begingroup$ @Alchymist Meteor impact , moonquakes and micro-meteorite erosion of the surface count as geological activity $\endgroup$ Aug 4 '15 at 15:11
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    $\begingroup$ @ManuelFaria: Not on the Moon they don't. $\endgroup$ Aug 4 '15 at 16:40
  • 1
    $\begingroup$ @LightnessRacesinOrbit Geology is a commonly accepted term for other celestial bodies. $\endgroup$
    – called2voyage
    Aug 4 '15 at 21:30
  • $\begingroup$ @called2voyage: Tell it to Alychymist! $\endgroup$ Aug 4 '15 at 23:34

You are correct about some of the sources of moon quakes.

NASA states there are are least four types of moon quakes:

There are at least four different kinds of moonquakes: (1) deep moonquakes about 700 km below the surface, probably caused by tides; (2) vibrations from the impact of meteorites; (3) thermal quakes caused by the expansion of the frigid crust when first illuminated by the morning sun after two weeks of deep-freeze lunar night; and (4) shallow moonquakes only 20 or 30 kilometers below the surface.

The first three were generally mild and harmless. Shallow moonquakes on the other hand are the problematic ones. They are the ones that can last for more than 10 minutes.

The reason has to do with chemical weathering, Neal explains: "Water weakens stone, expanding the structure of different minerals. When energy propagates across such a compressible structure, it acts like a foam sponge—it deadens the vibrations." Even the biggest earthquakes stop shaking in less than 2 minutes.

The moon, however, is dry, cool and mostly rigid, like a chunk of stone or iron. So moonquakes set it vibrating like a tuning fork. Even if a moonquake isn't intense, "it just keeps going and going,"

The reason for the shallow moon quakes and where they occur is unknown.

"The Apollo seismometers were all in one relatively small region on the front side of the moon, so we can't pinpoint [the exact locations of these quakes]."

It has been suggested that one possible cause may be the rims of large relatively young crater rims occasionally slumping.

  • $\begingroup$ I think the young crater rims slumping wouldn't produce a moonquake lasting 10 minutes. I read that tides might cause them but it seems that these specific moonquakes are localized and the tides affect the whole moon. Aren't there any other theories? $\endgroup$ Aug 4 '15 at 13:55
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    $\begingroup$ Yes, the sources are only speculating that slumping crater rims cause shallow quakes. The reason for the long during of quakes is the Moon is rigid and stiff. It contains no soft material to dampen quakes. The Earth has soft materials that dampen quakes so earthquakes only have a short duration in comparison. $\endgroup$
    – Fred
    Aug 4 '15 at 14:02
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    $\begingroup$ @ManuelFaria You might wanna check Spudis Lunar Resources and LPI's Moon 101 Lecture Series. There's many lectures and articles on the topic. My favorite theories for the long shallow quakes are collapsing lava tubes and impact crater melts, but there's plenty of other possible explanations for them. $\endgroup$
    – TildalWave
    Aug 4 '15 at 14:12

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