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Sunday, May 17, 2015

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The Earthquake House of Comrie

The United Kingdom is not generally associated with earthquakes, however, these islands are still rocked by a few hundred jolts a year, although only 20 or 30 of them could be felt by the population. Most of these are very small and cause no damage. Yet, the world’s first seismometer was built and installed in Scotland at a place called Comrie. A functional replica of it is still housed in the “Earthquake House”, built on the grassy slopes of The Ross.

The village of Comrie, in Perthshire, in southern Scotland, is one of the most geologically active area in the United Kingdom, due to its position astride the Highland Boundary Fault. It is the earthquake capital of the UK, being subject to more, and more earthquakes than anywhere else in these islands. Because of this it is sometimes referred to as the "Shaky Town".
The first recorded earthquake in Perthshire was made by one James Melville in July 1597, who had noted in his diary of an earthquake tremor felt across the county. It wasn't until 1789 that the first systematic recording of data and severity was recorded at Comrie. This was done by the Reverends Taylor and Gilfillan who began recording these tremors. Over the next 50 years they recorded as many as 70 major series of shocks, including the largest of all known Comrie earthquakes on 23rd October 1839. Many houses in Comrie were damaged and a dam near Stirling was breached. The shock wave was felt over most of Scotland.

With the Great Earthquake of 1839, postmaster Peter Macfarlane and shoemaker James Drummond, known as the ‘Comrie Pioneers’, set up an instrument to measure earthquake and began keeping formal records. Their instrument consisted of two wooden planks placed in the North-South and East-West direction. Over these, wooden cylinders of increasing width and therefore stability were placed. An earthquake would knock over cylinders up to a certain size and weight, which allowed the postmaster-shoemaker duo to measure the strength of the earthquake. A tray of sand prevented the cylinders from rolling about and knocking other cylinders off. It was primitive but it appeared to work.
In 1841, using the information gathered, they submitted a paper to the British Association for the Advancement of Science, which led to the formation of the Committee for the Investigation of Scottish and Irish Earthquakes. Over the years a number of instruments were built and used around Comrie, including the first modern seismometer that consisted of an inverted pendulum that wrote vibration onto a concave disk above. It was built by Scottish physicist James David Forbes.

But by 1844, seismic activity had declined and interest was lost, when a fresh series of tremors in 1869 renewed interest in earthquakes. New and more sensitive instruments were sought and in 1874 the Earthquake House was built on solid rock to hold the Mallet seismometer. Once again activity declined, and the site fell into disuse. By 1911 technology had moved on, and the building became redundant.

In 1988 it was decided that Earthquake House be restored and modern equipment supplied by the British Geological Survey were fitted. Visitors cannot enter the building but there are large windows through which one can observe the new instrument as well as the old wooden cylinder seismometer developed by Peter Macfarlane and James Drummond, set on the floor.


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