Here is a bit of background on the seismology of Moonquakes. The info comes from the book "EARTHQUAKES" by G.A. EIBY the retired superintendant of the New Zealand Seismological Observatory in Wellington city.

The seismometers that were placed and operating on the moon between Nov. 1969 and Sept. 1977. Three main causes of seismicity were discovered.
Impacts, Shallow (crustal)... 0-60km depth, and the deep events... 600-900 km depth. The deep ones seemed to come from a limited number of foci ~50 that are on the infered mantle - core boundary. The seismograms of different events from the same foci are almost identical with each other and each foci becomes active at some definite time each month. This inferes that tidal forces are the cause. There are peaks of activity 14 days apart and secondary peaks at 206 day intervals which would coincide with the Sun's contribution to the tidal forces.

The shallow events are thought to result from the release of crustal stresses. Only about a dozen of these events were recorded and no obvious patterns were seen. Moonquake seismograms are quite different from terresterial ones. The movements are much higher in freq., and reveberation continues for a very long time .... for the shallow and deep events up to 50 minutes and for impacts... well in excess of an hour for the larger ones. It was hard to pick phases and there were no clear surface waves, the very dry lunar surface is thought to be responsible.

The number of events recorded by each station per year varied between 600 - 2000 depending on the site. A major portion of these were very small and total energy released over a year was barely sufficient to produce a M2 quake. The text goes on to say that these numbers did not include the very small thermally induced events that accompanied the abrupt temperature changes at lunar sunrise and sunset. It is thought that these events resulted from small scale cracking and slumping of the surface. The crust was found to have an avg. 'P' - velocity of ~6.7km/s and the mantle has a fairly uniform 'P' vel. of ~ 8 km/s