Further tremors forecast after Irish Sea earthquake

An earthquake occurred in the Irish Sea overnight, sending tremors across the southeast region.

The epicentre of the quake, which registered at magnitude 3.8, was 15km away from the town of Abersoch in Gwynedd, the British Geological Survey (BGS) said.

“This was a larger than average earthquake, we get around one a year of this size,” the BGS said. “People have reported hearing an initial loud banging, followed by rumbling, and intense shaking.”

The earthquake happened at about 4.15am and tremors were reportedly felt in Dublin, Wicklow, Wexford and Kildare.

The Irish National Seismic Network said further tremors were likely to be experienced in the coming days in the Irish Sea and in north Wales.

Network director Tom Blake said the earthquake occurred some 97km southeast of Dublin but that its stations in Valentia, Donegal and Galway had all recorded it.

“The quake was measured at a depth of 8km and was followed four minutes later by a smaller 1.7 magnitude tremor at a shallower depth of 3km,” he said.

“The earthquake location is approximately 15 km west of the magnitude 5.4 earthquake that occurred on the Llyn peninsula on July 19th, 1984.”

Mr Blake said a 2.3 magnitude earthquake struck the same area on February 7th and that there had since been a number of tremors building up to this morning’s event.

Dr Brian McConnell, of the Geological Survey of Ireland, said there were conflicting reports as to the size of the earthquake, with the British reading coming in at 3.8 and the European reading at 4.2. He put the discrepancy down to the number of instruments recording the quake and said the difference would likely be resolved in time.

The shockwaves caused by the earthquake had travelled quite far relative to its size, he said, suggesting it may have been at the higher end of the reported readings.

Dr McConnell said it was fairly common to have smaller earthquakes registering at magnitude one, two or up to three that people do not hear about as they do not cause any noticeable effect.

“The Menai Straits Fault runs diagonally from Anglesea to Rosslare,” he said. “It has a long history of geological movement on it and is still active in a minor way.”