March 2023 Speaker
Adrian Wright is a local resident who after his retirement from teaching Geography at Colchester Grammar School a number of years ago has spent his time researching earthquakes across the world.
Adrian began by showing us diagrams of how various types of earthquakes can occur across the world and how their levels of magnitude can affect different areas of land and sea. In the early 1900s Guiseppi Mercalli developed one of the Earthquake Intensity Scales, whilst living in Naples where he closely studied Vesuvius, and produced levels from 1 to 12 of the intensity of the quakes.
He showed us a map where all the same intensity levels recorded from the Colchester earthquake were connected up and they formed an ellipse where the long axis was the Fault line and the Focus of the ellipse was the Epicentre of the volcano. The Colchester earthquake in 1884 was the strongest one ever to strike the British mainland and did catastrophic damage to Great Wigborough, Wivenhoe, Langenhoe Peldon and Abberton, and damaged many house roofs, churches and chimneys collapsed. The Lord Mayor of London raised £10,000 as relief for the sufferers which in today's money would be about £500,000. The fund helped about 20 churches and 1,000 properties.
In 1935 Charles F Richter developed a new earthquake scale which is still in use today. More recent events around the world have been the Tsunami in 1964 and the Christchurch, New Zealand earthquakes in 2011. Nowadays high rise buildings are reinforced with metal girders which will flex if an earthquake occurs. The good news is that the fault lines allow more gas and oil to move up to the surface of the earth but the bad news is that that the sea floor is spreading and the Pacific Ocean is getting smaller whilst the Atlantic Ocean is getting bigger.