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Earthquake House, Comrie,
Perthshire, Scotland
Historically, the Comrie area of Strathearn has experienced fairly frequent
earthquakes by UK standards.
James Melville recorded in his diary an earthquake felt across Perthshire
in July 1597. The first recorded Comrie shock was in 1788. The Rev.s Taylor
& Gilfillan documented the strange movements, noises and tremors around
the end of the 18thC.
With the 'Great Earthquake of 1839' The Comrie Pioneers, postmaster Peter
Macfarlane and shoemaker James Drummond, began to keep records.
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In 1841, a Committee for the
Investigation of Scottish and Irish Earthquakes was formed - the term seismometer
was first used, they discovered how to evaluate the Epicentre (a point on
the Earth's surface where the shock is greatest) and Prof J.D.Forbes designed
the first seismometer using an inverted pendulum writing onto a concave disk
above. |
| Over the years to 1844
a number of instruments were in use around Comrie. Things quietened so interest
was lost.
With renewed activity the
Committee began work again in 1869. New and more sensitive instruments were
sought. In 1874 the Earthquake House was built on solid rock to hold
the Mallet seismometer. |
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This consisted of two boxwood
planks N-S & E-W. Onto these, boxwood cylinders of increasing width and
therefore stability are placed. With a shock cylinders fall over up to a
certain width and this allows a measurement of the strength of the earthquake.
Sand around the planks 'catches' the cylinders and prevents them from rolling
and knocking down others. Simple but very effective. |
| Technology became
more sophisticated with time. From 1911 the building had become redundant
and fell into disrepair.
In 1988 it was decided that
Earthquake House be restored and modern equipment was supplied by
the British Geological Survey. Large windows have been fitted so the visitor
can observe both the old and new seismometers installed.
Fortunately the damage done
by Comrie quakes has been minor. But why does this area experience them?
Up until the last century,
scientists were unsure about the source of earthquakes. Were they geological
or meteological? |
Pioneer James Drummond believed
they were the explosions of natural gas underground. As evidence accumulated,
it became clear that they were the result of movement of great fractures
in the Earth's crust called Faults. There is resistance so the two sides
move in infrequent jolts - releasing built up energy as earthquakes. |
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In fact it was not until the
formulation of the theories of Plate Tectonics in the 1950s & 60s that
a full explanation was offered. Great crustal plates move across the Earth's
surface floating on the semi-molten layer below. Where these 'scrape and
grind' together the great earthquake zones - of say Japan and California
- occur.
But what about Comrie? The
great Highland Boundary Fault which separates the Highlands from the Lowlands
lies just outside Comrie. This fault was highly active 400Myears ago when
Strathearn like much of Britain was a hot dry desert. At that time the Fault
must have been driven by global plate movements. Are the quakes just some
minor settling of this once great fault? Possibly.
The epicentres lie just north
of Comrie while the movement is actually about 15km down. The HBF lies on
the surface just to the south of the town. The HBF is actually very complex
and may slope northward with depth. Alternatively another unknown fault may
exist at depth and be causing the shocks. This theory is supported by many
geologists on the basis that the HBF is inactive elsewhere.
Now visit the
Comrie page on this site.
Other places to visit...
Macrosty Park
Muthill Church
St Bean's Church
Innerpeffray Library |
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