The MVGS is now the proud owner and operator of its own seismograph ! We have bought a RaspberryShake 3D (see https://raspberryshake.org/products/raspberry-shake-3d/ for details) using a grant that we got from the GA (the Geological Association, of which we are a registered Local Group). In order to test out the seismograph, I have temporarily set it up in my hallway (ground floor, solid, uncarpeted floor, see picture below).
It is connected up to the worldwide network of citizen science seismographs and you can see its current output by visiting https://raspberryshake.org/community/station-view/, zooming in on our area on the map and selecting the seismograph NORTH of Dorking (there is already one to the south), between Guildford and Leatherhead. Its identifier is AM.RD0B6. On the location map shown below you will see that, in general, the background ground motion of our siemometer, i.e. the amount of signal shown by the colour of the triangular symbol, is quite low compared to others in and around London, including the one south of Dorking. This is a reflection of the amount of high frequency noise present at most of the stations (traffic and other human activity), which is generally at a low level out in the countryside, away from main roads. But that does not mean that there isn’t still a fair amount of noise.
The third image below shows the first 24 hours of recording. You can clearly see how 'quiet’ it gets at night, with very little going on, compared to daylight hours, when even the roads around here get busy. I can’t imagine what a similar display for one of the London seismographs looks like
With all of this ’noise’, you might wonder whether the seismograph is actually any use: would it even see an earthquake ? Well, fortunately the noise is mostly high frequency while earthquakes are low frequency and clever bits of software can distinguish between them. The really big peaks on the seismogram all include low frequency signal. Are these actually earthquakes but a long way away ? Probably not - but some may be…
You will see what earthquakes look like in the next section.