More earthquakes on the way

Tuesday 29 July 2014

Jersey should expect more tremors over coming weeks as the earth settles down after two of the area’s biggest quakes in a century, according to the Met Office.

The Island was hit with earthquakes of a magnitude of 4.2 on the 11 July and of 3.2 on 23 July. These were followed by a wave of up to eight smaller tremors of a magnitude of between one and two.

Tony Pallot, Senior Forecaster at the Jersey Met Office said: “You expect a series of small tremors over the course of a year but there seems to be a lot of activity at the moment on the line which runs between Corbière and the Minquiers to Coutanches in France.

“Mostly these are minor tremors of less than a magnitude of one, something most people wouldn’t even feel.  It’s all down to the ancient plates and tectonic movements from millions of years ago. The rock structures are still settling down.

“Occasionally you get a bigger movement. On average, you would only expect bigger movements every 30 years or so. I was a bit surprised at the one at 3.2 last week but I wouldn’t be surprised if we see further small tremors.”

In 1853 Jersey recorded an earthquake with a magnitude of 5.2, followed by one of 5.1 in 1926 and another of 5.2 in 1933. The area around the British Isles gets 150-200 earthquakes a year.

David Galloway, Seismologist at The British Geological Survey, said: “In UK and European terms these were quite big earthquakes and what you are getting now in Jersey is probably the aftershocks. The area between Northern France and Jersey gets earthquakes on a frequent basis but most of the time these are not felt.

“We don’t get the really big earthquakes like in Turkey because we’re on the middle of a tectonic plate rather than being at the edge where 95% of the big earthquakes happen.

“There are two theories why earthquakes happen around Britain. One theory is that the tectonic plates are moving which stresses the rocks so an earthquake occurs at their weakest point. The other theory is that the land is trying to get back to the levels it was at before glaciers compressed it during the ice age – Isostatic Rebound.

“We live on a dynamic planet. The earth’s plates move about 3cm a year, about the same rate fingernails grow, and thus creates stresses and activity.”