Yesterday Philip and I went to the excellent lecture by Prof. Dan McKenzie given in my old workplace at The Cavendish Labs. I also got to ride a Segway, but thats another story! The lecture was the final event in the Cambridge Science week.
Dan started with a slide of of Hess’s work which got him started as a post graduate in 1967 and explained how he developed the theory of the spreading ridge and how the seismometers developed for detecting underground nuclear tests proved to be invaluable for determing the precise position of all the earthquakes in the world. Showing that in the oceans, for example, they form a beautiful line midway between Africa and The Americas.
He then explained how the subvention of the tectonic plates lead to one plate sliding under the other, the lower plate sticks and then pushing the top plate down with it (loading). Eventually the force is to great and the upper plate pings free (unloading) causing an earthquake and the land on the top plate to return to its original level. Fascinating stuff.
Even more amazing is that on land, especially in Iran etc due to the plates rubbing against each other and producing clay, surface water is trapped. Hence Oasis’s are formed at faults which lead to cities and towns been built around them with the unfortunate consequences like Bam, where the city was levelled by an eathquake to such an extent that the streets could not be identified and 40,000 were killed. Even so he showed a picture of where a new hospital has been built right across a fault line.
He went on to the depressing tale of the Tsunami in Indonesia with a story of how one of his colleagues saved the occupants of the hotel were they were staying because he saw the signs, apparently you have about 16mins – the sea goes out for 15mins and returns as a 7metre wave in 1 min.
Then showed a chart plotting the earthquake trend moving down the faultline. with the next quake predicted to hit close to Sumatra any time soon with his gloomy estimate of 1million casualties. Similar charts were shown for along the Pakistan India region.
What can be done? build better houses, for 10% more cost houses can be made more earthquake resistant. Educate the children to nag their parents into doing it! Education prevents cheating when building. Large buildings can be built on lead which allows movement.
He expressed amazement at how quickly his work has been accepted. In less than 40 years its gone from theory to now been taught in primary schools!
The science week has been a tremendous success tThe Cavendish must have had hundreds of visitors all making balloon powered Wacky Racers and testing their strength against a vacuum.