Scientists have discovered more earthquakes occur Britain and in the north of Ireland because the solid outer part of the earth is thinner there.
Researchers from the Dublin Institute for Advanced Studies and the University of Cambridge made the discovery when trying to figure out why seismic shakes occur more frequently in Britain compared with here.
They found that variations in the thickness of tectonic plates, which are also known as lithospheric plates, relate directly to the distribution and risk of earthquakes in Ireland, Britain, and around the world.
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The research team used a technique called “seismic tomography” which uses seismic waves generated by earthquakes to create computer-generated 3D images of Earth’s interior.
The data they collected revealed variations in the thickness of the solid outer part of Earth across Ireland and Britain.
The experts found the lithosphere, which is the rigid outer part of the earth consisting of the crust and upper mantle, under southern Ireland was cold, thick and mechanically strong.
Whereas, across the water in Britain, it was thinner, warmer and weaker - which led to more earthquakes.
They also discovered the lithosphere in the north of Ireland was thinner than the rest of the country.
Western Britain has a relatively thin lithosphere and has reported numerous earthquakes whereas southeastern England and eastern Scotland has thicker crust and as a result has fewer shakes.
Last month, a 2.5 magnitude earthquake rocked Donegal. There was another 2.5 magnitude shake in Donegal on January 26, 2012, which took place on the Fanad peninsula.
In 2019, two earthquakes struck Donegal twice in the space of just three weeks. The first one took place on April 7 and had a magnitude of 2.4 with the epicentre in Donegal Bay.
While the other took place inland on April 29, 2019 and had a magnitude of 2.1
The county has previously been described as the most seismically active region in the whole of Ireland.
Elsewhere in the country, a magnitude 4.0 magnitude earthquake that happened off the west coast of Ireland in June 2012 led to tremors being felt in Mayo, Galway, and Sligo.
And in 1984, there was a 5.4 magnitude earthquake that occurred in the Irish Sea. It is believed to be the most powerful one ever felt in Ireland.
It was so powerful, it was felt along the east coast of the country and as far inland as Kildare.
The quake went on for around 30 seconds and was followed by several aftershocks.
The Irish National Seismic Network, which is operated by the Geophysics section at Dublin Institute of Advanced Studies (DIAS) with help from the Geological Survey Ireland, is the group responsible for monitoring earthquakes in this country.
INSN has six seismic stations around Ireland. The strength of an earthquake is measured on the Richter scale.
It goes up by factors of ten which means a 2.0 magnitude earthquake is tens times stronger than a 1.0 magnitude quake.
Professor Sergei Lebedev of DIAS and the University of Cambridge, who led the team, said, “After 100 years of research, seismic tomography has provided the answer to the long-standing puzzle of why Ireland and Britain’s seismicity is uneven.
“Ireland and Britain share their tectonic history and are both far from active plate boundaries, however, the distribution of earthquakes is not what you would expect.
“Discovering the cause of these variations is important for our understanding of the basic mechanisms of earthquakes that occur within stable continental interiors and for assessing hazards in various regions prone to seismic activity.
“Our knowledge and data on the distribution of micro-seismicity within Ireland and its underlying causes have been uncertain due to a lack of sampling of the island, until recently.”
He added: “We’ve been able to use the data from recently deployed seismic stations in Ireland such as the DIAS station at Inch Island, Donegal, and map the seismicity of Ireland in greater detail than ever before.”
It comes as Professor Chris Bean described the findings as “highly significant”.
Prof Bean, who is also the Head of Geophysics at DIAS, explained: “These research findings are highly significant as they show that even within the same plate, local details are important.
“We now have the reasoning behind why more earthquakes are occurring in Britain than in Ireland and new insight into where the likelihood of occurrence is higher.”
Researchers said the breakthrough can be applied around the world in forecasting and shed a new light on the basic mechanisms of seismicity distribution.
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