Impulsive quakes on Earth have a characteristic waveform which this does not match: The arrival of a compression wave, followed by a larger shear wave. That waveform wouldn't be much different on another planet, since the shape of the waveform arises from the mechanical properties of rock. If it were not a rockfall, it would have to correspond more to a seismic tremor, which happens more slowly-- I know less about those and I am curious how this matches up.
Having multiple stations would really help to narrow down what the source of sounds like this could be.
Fascinating, I wouldn't have thought these would be measurable on a large area's scale.