On the 17th February 2018 an earthquake with magnitude 4.4 occurred at 14:31:07.6 UTC at a depth of 7.4km in South Wales about 20km north of Swansea, see map below. According to the BGS hundreds of members of the public submitted felt reports. Events of this magnitude happen in the UK only about every 2 to 3 years. The BGS reports that this is the biggest event in the area since a magnitude 5.2 earthquake in 1906.
The earthquake was recorded at stations of the Irish National Seismic Network (INSN), see seismic waveforms below (select figure to enlarge).
Further information about this event is available from the following webpages:
The drumplot below shows the unfiltered seismic signal recorded on the 17th February 2017 at INSN station DSB in the Dublin mountains. The high amplitude low frequency signals between midnight and 1 a.m. are the surface waves of the M7.2 Mexico earthquake that occurred on the 16th February 2018 at 23:39:39, see https://www.insn.ie/2017-02-16-m7-2-mexico for more details on that event. The magnitude 4.4 event with epicentre in South Wales can be seen with much higher frequency content around 14:32.
More information about the INSN is available via this link.