Vibrations couldn't be detected

10:12am Thursday 12th January 2012

WAS intrigued by the letter from Ken and Julie Marsh reporting their house shaking (Postbag, January 5).

We have been recording ground vibrations at Bishop Wordsworth’s School for the past two years using a seismometer designed by the British Geological Survey to detect earthquakes. During that period we have recorded 160 earthquakes, mostly in the Far East. There were no strong vibrations in the early hours of New Year’s Day.

Strangely, there was a UK earthquake in the Bristol Channel which shook and awakened a number of people in north Cornwall and Devon, just before midnight on January 5. The most forceful recent shaking in Salisbury was at 8am on July 14, 2011 produced by a magnitude 3.9 earthquake in the English Channel midway between Portsmouth and Le Havre. Even so, the vibrations were only a quarter of the size at which they would be felt here.

Ground vibrations are produced by many events both natural and manmade. Ocean waves continually pound the west coast of the UK. Other schools have detected vibrations caused by repairs to gas mains, cheering football crowds and the Reading Rock Festival.

For our part, we spotted a regular shaking every Sunday morning. An interested student contacted the lead bell-ringer at a church whose worship started when the shaking stopped. He was informed of the time of the forthcoming special peal to celebrate the enthronement of the new bishop.

This was duly detected so it became beyond reasonable doubt we regularly record the vibration caused by swinging two tons of bells at St. Thomas’s Church some 600m away.

We were kindly invited to measure the vibrations in the bell tower itself to confirm this.

Yes, the ground was shaking under our feet as the team at St Thomas’s Church rang out the old year and rang in the new but only by a thousandth of the distance needed to be felt.

RICHARD WARD Bishop Wordsworth’s School

IN reply to Kevin and Julie Marsh’s letter (Postbag, January 5), I also felt the tremors. In fact, they woke me up. Having experienced them in New Zealand, I knew at once what they were. I was very surprised to feel them here in Salisbury.

MARION DANSON Salisbury

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