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.
But why Comrie? Well up until the last century, scientists were unsure about the source of earthquakes. Were they geological or meteological? A Pioneer called James Drummond believed they were the explosions of natural gas underground. However, 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.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.
The great Highland Boundary Fault which separates the Highlands from the Lowlands lies just outside Comrie. This fault was highly active 400M years 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.
In order to log this cache, please message me with the answer to the following question, and take a photo of yourself/GPS and the Earthquake House to add to your log.
What complementary fault forms the southern boundary for the Central Lowlands?