Moher meter picks up Mayo earthquake

The strongest earthquake ever recorded in the West of Ireland was picked up by the recently installed seismometer at the Cliffs of Moher.

The magnitude 4 subsea earthquake struck shortly before 9am on Wednesday about 60 kilometres west of Mayo. The tremor was recorded at a depth of three kilometres.

It’s the second significant earthquake in as many years to hit the west of Ireland. The 2.7 magnitude trembler in May 2010 in Lisdoonvarna, just six miles from the Cliffs of Moher, remains the strongest onshore earthquake recorded in Ireland since records began in 1978. It was also the first earthquake to be recorded in the southwest of the country since records began in 1978.

Commenting on Wednesday’s quake, Tom Blake, INSN director and experimental officer with the School of Cosmic Physics at the Dublin Institute for Advanced Studies (DIAS), stated, “This is the first event recorded in this area and was felt onshore by quite a number of people. There are some reports of minor structural damage, which have not been confirmed.”

The largest earthquake felt in Ireland occurred on the July 19, 1984 with a magnitude of 5.4, and was located off the coast of Wales. It also caused minor structural damage on the east coast of Ireland.

“Although Ireland does not sit on any major plate margin, it is still susceptible to earthquakes, as we saw in Mayo today and in Clare in 2010. The Cliffs of Moher seismometer was certainly well placed to register and record this week’s earthquake. This was a very important seismic event, as it was the first time that a tremor had occurred in this region since records began,” said Mr Blake.

Cliffs director Katherine Webster points out that while the seismometer detects the earthquake, it does not register the size.

“We can’t really tell from our one reading what the magnitude of the quake would be. To get that information you need readings from at least three seismometers and it’s a relatively complicated calculation so we leave that to the experts but the Dublin Institute of Advanced Studies registered it as magnitude 4,” she told The Clare Champion.

“The graph, once filtered, is quite dramatic but the background noise from the visitor centre being open had to be filtered out to be able to get a clear view. Some earthquakes that happen in the middle of the night our time when the centre is closed are easier to see without filtering as there are minimal vibrations from human activity in the vicinity of the seismometer,” Ms Webster explained.

The Cliffs of Moher does not count the number of quakes detected by the seismometer because of the high volume.

“Whenever there is a notable quake that the Irish Seismic Network wants information on from our graph, we would upload that information to the IRIS website. Since the seismometer was installed in February we would have done this about a dozen times,” Ms Webster added.

The seismometer can be viewed by the public and according to Ms Webster is a welcome addition to the Cliffs of Moher Visitor Centre.

“We get a considerable amount of interest from visitors, especially after a specific event that has had a lot of media coverage, like the recent earthquakes in northern Italy. The seismometer features in our tours and is always something that visitors are very interested in when the information they are seeing is explained to them,” she concluded.

The DIAS began modern seismic recordings in 1978. The Irish National Seismic Network (INSN) now features five permanent stations in Dublin, Kerry, Galway, Donegal and Wexford, along with 55 other seismometers around the country.