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The abstract of the new Nature Geoscience paper Shallow seismic activity and young thrust faults on the Moon reads:

The discovery of young thrust faults on the Moon is evidence of recent tectonic activity, but how recent is unknown. Seismometers at four Apollo landing sites recorded 28 shallow moonquakes between 1969 and 1977. Some of these shallow quakes could be associated with activity on the young faults. However, the epicentre locations of these quakes are poorly constrained. Here we present more-accurate estimates of the epicentre locations, based on an algorithm for sparse seismic networks. We found that the epicentres of eight near-surface quakes fall within 30 km of a fault scarp, the distance of the expected strong ground shaking. From an analysis of the timing of these eight events, we found that six occurred when the Moon was less than 15,000 km from the apogee distance. Analytical modelling of tidal forces that contribute to the current lunar stress state indicates that seven near-apogee events within 60 km of a fault scarp occur at or near the time of peak compressional stresses, when fault slip events are most likely. We conclude that the proximity of moonquakes to the young thrust faults together with evidence of regolith disturbance and boulder movements on and near the fault scarps strongly suggest the Moon is tectonically active.

Question(s): I'd like to understand

  1. what young thrust faults are
  2. how one can decide that there is a fault on the Moon (apart from the "evidence of regolith disturbance and boulder movements on and near the fault scarps")
  3. what one might use as evidence to classify a fault on the Moon as a thrust fault
  4. how might one decide that the thrust fault is also young

The Nature Geoscience paper is paywalled, but there is some additional discussion in Phys.org's The moon is quaking as it shrinks


Some background on the seismometers on the Moon:

below: images from ALSEP, Apollo Lunar Surface Experiments Package, 20 November 1969 – 30 September 1977, by Hamish Lindsay, Click for full size.

NASA scientists Lunar data NASA Lunar seismogram

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    $\begingroup$ pages.uoregon.edu/millerm/Tfaults.html. $\endgroup$ – gansub May 14 '19 at 4:20
  • $\begingroup$ @gansub lovely! $\endgroup$ – uhoh May 14 '19 at 4:37
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    $\begingroup$ I think we must place earthly "thrust faults" and "tectonic activity" in relation to the lunar terms. It appears that the lunar ones are caused by tidal forces alone and are rather shallow, while much more extensive and energetic processes drive the earthly ones. Searching "lunar thrust faults" and "lunar tectonic activity" resulty in too many hits for a specific answer, i am sorry. "Significance" is qualitative, would it be possible to specify e.g. "what causes" or "how string" ... ? Good subject. $\endgroup$ – a_donda Apr 30 at 9:10
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    $\begingroup$ @a_donda I've edited the Questions: section of the text, breaking it down and removing "significance". Feel free to edit further if it helps lead towards an answer. Thanks! $\endgroup$ – uhoh Apr 30 at 9:37
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    $\begingroup$ Ok. A thrust fault typically occurs in areas of compression. They are pretty well observable, especially when there's no annoying plant or soil cover and grazing light accentuates the structure. $\endgroup$ – a_donda Apr 30 at 9:58

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