Aftershocks from two earthquakes that struck off the Fylde coast may be felt for days to come, it has been claimed.
The Irish National Seismic Network (INSN) said the quakes, which occurred 25km west of Fleetwood in the Irish Sea, were probably caused by stresses built up from the weight of glaciers covering land during the Ice Age.
INSN director Tom Blake said it was unusual that the earthquakes - measuring 2.4 and then a stronger 3.3 on the Richter scale - happened in the Irish Sea.
“It is impossible to tell if stronger earthquakes will occur in the coming days and weeks, but aftershocks can be expected even if most, if not all, will be too weak to be felt,” Mr Blake said.
The strongest quake, at a depth of 5km, was recorded by the British Geological Survey shortly before 10am.
The earlier and smaller quake was recorded at around 5.30am.
The tremors were felt in Fleetwood, Blackpool, Poulton, Thornton, Cleveleys, and as far away as Cumbria.
The larger earthquake was also recorded by INSN seismometers as far away as Donegal and Wexford in Ireland.
Suggestions the shocks were caused by seismic testing in the area have been dismissed.
Energy firm Halite, is due to finish its exploratory work, involving a series of controlled explosions to test the nature of the bed rock Over Wyre, this week.
Keith Budinger, chief executive of Halite Energy, said: “Our seismic survey work is only at a six metre maximum depth.
“The tremors were nothing to do with our work, it’s just too shallow.”
Read how The Gazette reported the earthquakes: