adrian paniwnyk
Member
I noted with interest on the Pikedaw Calamine Caverns thread that an article on earthquakes and caves is due to appear in Descent.
My own personal experience of an earthquake underground was in Ogof Igam-Ogam in the Little Neath River valley on the 17th Feb. 2018. The cave is situated on a major fault which comes off the side of the Neath Disturbance. A group of four people including myself were near to Sump 4 in this cave. Malcolm Stewart was packing up his kit after finally passing the sump after a gap of some 30 years. We were just about to leave, when all four heard a deep ominous bang. The sound lasted about 10 seconds, starting out quite loud and then dying away, while this was happening the walls did not shake or vibrate.
My initial thoughts that the bottom of the cave being some 30 metres below the level of the riverbed was flash flooding but when water levels did not rise, it did occur to me that a large collapse may have occurred in the entrance choke regions thus sealing us in.
As you can imagine a rather worrying exit was made whilst trying to push a dive cylinder through the various contortions of the cave.
Back on the surface, we quickly learnt that what we had heard had been a shallow, minor earthquake, magnitude 4.4 with an epicentre 20 km NNE of Swansea.It was apparently felt as far east as London and was widely mentioned in the press Maybe the effects of shallow earthquakes causes more pronounced effects at the surface but I'm not totally sure about this. Certainly with a more powerful earthquake our safe exit might not have been assured!
Please note, I have written this as part of a longer article about recent and past explorations within Ogof Igam-Ogam which is going to appear in the Croydon Caving Club magazine Pelobates, hopefully in the not too distant future!
My own personal experience of an earthquake underground was in Ogof Igam-Ogam in the Little Neath River valley on the 17th Feb. 2018. The cave is situated on a major fault which comes off the side of the Neath Disturbance. A group of four people including myself were near to Sump 4 in this cave. Malcolm Stewart was packing up his kit after finally passing the sump after a gap of some 30 years. We were just about to leave, when all four heard a deep ominous bang. The sound lasted about 10 seconds, starting out quite loud and then dying away, while this was happening the walls did not shake or vibrate.
My initial thoughts that the bottom of the cave being some 30 metres below the level of the riverbed was flash flooding but when water levels did not rise, it did occur to me that a large collapse may have occurred in the entrance choke regions thus sealing us in.
As you can imagine a rather worrying exit was made whilst trying to push a dive cylinder through the various contortions of the cave.
Back on the surface, we quickly learnt that what we had heard had been a shallow, minor earthquake, magnitude 4.4 with an epicentre 20 km NNE of Swansea.It was apparently felt as far east as London and was widely mentioned in the press Maybe the effects of shallow earthquakes causes more pronounced effects at the surface but I'm not totally sure about this. Certainly with a more powerful earthquake our safe exit might not have been assured!
Please note, I have written this as part of a longer article about recent and past explorations within Ogof Igam-Ogam which is going to appear in the Croydon Caving Club magazine Pelobates, hopefully in the not too distant future!
4.4 is a big one for the UK.
