This image compares the vibrations from a passing train, measured at a distance of 150m, to a simulated earthquake occurring 2km below Cuadrilla's Balcombe drilling site (from the Bristol University Balcombe baseline study). We found that the train vibrations had similar amplitude to a magnitude 1.5 earthquake, equivalent to the second quake that lead to the shut down Cuadrilla's operations in Blackpool in 2011 (and a two-year moratorium).
So there is a risk that trains passing by could also ovalise the casing? Goodness!
ReplyDeleteThe first quake at Preese Hall had a magnitude 2.3. I find it strange that you forgot to mention that. Does that information not suit your thesis?
ReplyDeleteIts just irrelevant. Shale, being a soft rock, cannot generate large earthquakes. For that you need hard rocks that will lock up until they shear. 2.3 is still classed as ' very slight' and to start getting minor damage to buildings you need intensity 5 and above. Each single unit is an order of magnitude difference.
ReplyDeleteWhen the first Preese Hall event occurred, the nearest monitoring station was approximately 70km away. The amplitude of seismic waves decreases with distance, so the recorded waveforms from the first event are substantially smaller, and a comparison with the train recorded at a distance of 150m would be meaningless.
ReplyDeleteBy the time the second event occurred, the BGS had installed a monitoring station fairly close to the well (I forget the exact number, but within a km or two). It makes a lot more sense to plot the waveforms from nearby stations to compare against the train, and that is what I have done.
Had the 1st, M2.3 event been recorded on local stations, I would have happily plotted it as well. I am as disappointed as you are that no seismic monitoring stations were deployed, but I can understand the why this wasn't done - in the US hundreds of thousands of HVHF have been performed without induced seismicity. I am happy that the new traffic light scheme will require seismic monitoring around all future operations
The Roseacre group are using a leaflet claiming 100 houses were damaged by the Preese Hall megaquake :) (Roseacre is where Cuadrilla are working near Elswick)
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