Seismic activity on the Moon?

I was looking over some of the photos taken by NASA's Lunar Orbiter V from 1968 and came across this picture:



The high resolution version of the image can be downloaded here.

When I started zooming in on the image, I noticed some strange cracking near one of the larger surface depressions. The area I'm referring to looks like this:

[atsimg]http://files.abovetopsecret.com/images/member/281e99a11553.jpg[/atsimg]

It looks like the same type of cracking that happens when an large earthquake happens on Earth (image). However, we are told that the moon has no plate tectonics, therefore seismic activity should be practically non-existent. So how can these cracks be forming in the surface?

I think what we see in the image are "rilles" not cracks, and the rilles are a result of earlier vulcanic activity on the moon:

A common and intriguing volcanic landform found in the lunar maria are narrow, winding valleys called sinuous rilles. These range in width from tens of meters to 3 km, and in length from a few kilometers to 300 km. Many originate in irregular craters.

One of the largest of these rilles is Hadley Rille in the Imbrium basin, which was visited by Apollo 15 astronauts. Although most workers believe that the sinuous rilles are a combination of lava channels and collapsed lava tubes. However, the mode of lava channel formation remains controversial. Some believe that the channels are "constructional" due to the build up of lava levees along the sides of the channel. However, the majority of the sinuous rilles are thought to the product of thermal erosion of the mare surface by exceptionally hot, fluid lava.

Hadley rille:
[atsimg]http://files.abovetopsecret.com/images/member/6b0189df41c6.gif[/atsimg]

www.geology.sdsu.edu...

NASA's own site has an article about the seismic activity on the moon.

March 15, 2006: NASA astronauts are going back to the moon and when they get there they may need quake-proof housing.

That's the surprising conclusion of Clive R. Neal, associate professor of civil engineering and geological sciences at the University of Notre Dame after he and a team of 15 other planetary scientists reexamined Apollo data from the 1970s. "The moon is seismically active," he told a gathering of scientists at NASA's Lunar Exploration Analysis Group (LEAG) meeting in League City, Texas, last October.

NASA - Moonquakes