Scientists may have discovered the cause of more than 100 mysterious earthquakes that shook the UK.
Following the tremors, cracks appeared in the walls and ceilings of Surrey homes, and there were reports of houses and beds shaking.
The quakes in Newdigate and surrounding areas from April 2018 until early 2019 measured between 1.34 and 3.18 magnitude.
Geologists had been divided over their cause, but a new study published in Geological Magazine concluded that oil extraction from a nearby well may have triggered the events.
UCL researchers ran more than a million simulations estimating the frequency of earthquakes based on the timing and volume of oil extraction. They found the model predictions roughly matched what occurred.
Lead author Dr Matthew Fox said: “Our study suggests there is a link between the earthquakes and oil extraction at Horse Hill but we cannot rule out that this link is a coincidence.
“More work needs to be done to understand if this is cause and effect. However, our findings indicate it is plausible that oil extraction triggered the earthquakes.”
Oil extraction causes changes to fluid pressure in the rock, which can diffuse through tens of kilometres underground to intersect a fault.
Even a small change in stress at a fault line can cause the rapid movement of rock that leads to an earthquake.
Oil extraction at the Surrey site was stopped in October after Supreme Court judges ruled that the full climate impact of the project should have been considered before Surrey County Council approved it.
However, another project has received council approval to conduct exploratory oil drilling in Balcombe, West Sussex. This is subject to a legal challenge by a residents’ group, the researchers said.
The research was complicated because instruments to detect ground vibrations were installed in the area only after the first larger earthquakes had occurred.
Study co-author Professor Philip Meredith of UCL Earth Sciences said: “Our study highlights the importance of monitoring the seismicity of areas where oil extraction might occur before any works start.
“Caution should be the byword. It is no good saying you don’t have a problem when you potentially do.
“There has been no significant seismic activity in Surrey for decades, so these earthquakes were unusual events. However, unusual events do happen in nature, so we can’t rule out the possibility that the timing associated with the oil extraction was a coincidence.”
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