We’ve done this before, spathi.
“How much of a tremor is enough to stop?”
Not one of magnitude 1.5.
Earthquakes occur in the UK all the time. In the summer in a period of twelve weeks there were seven earthquakes in Surrey, all of which were stronger in magnitude than the one you mention, some more than twice as strong:
https://www.bbc.co.uk/news/uk-england-44727326
Tremors of between 1.0 and 1.9 on the Richter scale are described as “Microearthquakes” and are very rarely felt by humans. They are detectable only by seismographs and several million occur worldwide every year. Some seismologists believe there are at least twenty of these shocks occurring every moment of every day across the globe. Extracting shale gas is bound to cause some seismic disturbance but to become hysterical over such minor events and suggest the activity should be abandoned is ludicrous.