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Size matters when it comes to seismology, say researchers who have found that the frequency of earthquakes relates to tectonic plate thickness.
A study carried out by researchers at the Dublin Institute for Advanced Studies (DIAS) and the University of Cambridge provides new insights into why Ireland gets fewer earthquakes than its nearest neighbour.
The research team used a technique called seismic topography. This involves the use of seismic waves generated by earthquakes to create computer-generated 3D images of the Earth’s interior.
The scientists looked at the thickness of tectonic plates and how they impact the frequency, distribution and risk of earthquakes around the world. Tectonic plates moving and colliding together is the cause of earthquakes. These plates make up the Earth’s lithosphere, or thin outer layers.
While carrying out their enquiries, the scientists noticed that there was a significant difference in the thickness of the tectonic plates lying underneath Ireland and Britain.
Most of Ireland has a cold, thick, mechanically strong lithosphere whereas most of Britain has a thinner, warmer lithosphere. This could explain why Ireland gets fewer earthquakes than England.
The lithosphere underneath the northern part of Ireland is also thin and weak, which explains why that part of Ireland gets more earthquakes than the southern part.
Western Britain also has a relatively thin lithosphere and is more often affected earthquakes than other parts such as the southeastern of England and the east of Scotland, which have a thicker lithosphere.
“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,” said Prof Sergei Lebedev of DIAS and University of Cambridge, who led the team.
“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.”
He also said that until recently the knowledge and data on the distribution of seismicity within Ireland has been “uncertain due to a lack of sampling of the island”.
“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.”
The project research paper has been published in the Geophysical Journal International. The study received funding from Science Foundation Ireland.
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