While analyzing some data of acoustic injection recently performed in WEB, we noticed that there was a big low frequency seismic noise in quite all sensors (see plot 1).

This noise has nothing to do with our acoustic emission (it is quite impossible to "shake" the concrete floor at these frequencies) and forced the IP controls to counter it (as example, see Sc_WE_MAR_TX_CORR and many other signals in the previous plot).

This seismic noise is found mainly in the 1-10Hz region and, looking for some occurrence, we noticed that it occurs in working hours (from 8:00 am to 08:00 pm LT) starting from August 18 (see plot 2).

We also looked at the seismometers of other buildings (CEB, NEB) but this noise is not present.

Moreover, this morning (August 21) the noise has increased a lot, now more in the Horizontal than in the Vertical direction: even the "signature" is different (see plot 3).

Convinced that these noises are of anthropic origin, we decided to take a tour around the WE building in search of "human" activities.

We found indeed a first guilty (see photo 1): a FIAT-HITACHI excavator working outside the fence. We asked the worker for some information (and this was at 10:33 local time, so he was forced to stop using the machine), and he confirmed that the work started this morning, lasting a couple of days. A posteriori we have verified that the big noise disappeared exactly for a few minutes at 10:33 local time.

We also were luckly enough to meet a tractor running on the road parallel to the Virgo fence (see photo 2), holding many hay bales; we stopped the girl driving, and she confirmed us that starting from Sunday morning (at 8am) she, toghether with some other farmers, ran many times with the tractor on that road. She told us that, even in this case, the work will remain for a few days, until all the bales are placed in the sheds.

For a map showing the exact location of the villains, see photo 3 and photo 4.

The distance from the WE tower was about 80 meters for the tractors and about 180 meters for the excavator. Quite nothing is visible at glance in Hrec (see plot 4), but a more in-depth analysis would be useful.