Some time ago, amongst other academics, I was approached by the staff at the UN for advice on earthquake prediction following the Indonesian quake and tsunami. Those of you that have looked at my biography will know that my speciality is deep crustal structures, specifically major fault zones like the subduction zone off Sumatra. I advised that before any predictions could even be contemplated that a greater understanding of the detailed structure must be obtained. This is a difficult process, ascertaining the nature of the subduction zone 10-30km below the surface is not an easy one. Luckily the oil industry has been carrying out such surveys, usually only to 10km depth or so offshore in sedimentary basins, for a number of years so the base technology is well known.
In my own research I use a system known as ‘3-D seismic tomography’ which basically involves setting of large explosions, or often at sea using large compressed air guns, to send shock waves through the ground which are then reflected back to a 5km or so array of geophones towed behind the boat. Variation in the return time for the shock waves indicates changes in the velocity of the waves within the rocks, changes of velocity indicating changes in the nature of the rock and its possible structure. Many thousands of explosions have to be made while travelling along grids. The amount of data produced is mind-boggling and requires incredible computing power (a Cray) to analyse. When analysed a 3-D image is produced of the probable structure of the rocks. Well that’s the theory!
Following the second major quake further along the subduction zone, and the likelihood of more to follow, it became urgent that the nature of the fault was ascertained particularly as the first quake produced a tsunami and the second did not. What was the difference in the shape and nature of the two areas that caused one to produce the tsunami and not the second? These are questions that need urgent answers.
A seismic survey ship has been hired from the oil industry (at a cost of about $40k per day!) and is now setting off to the area and I have been asked to go and supervise the collection and analysis of the data on behalf of the UN and the British Geological Survey. I fly off to South Africa to meet the boat on Monday. The data collection should take 6-8 weeks if the weather is kind so I’ll be off forum for a while.
I thought I ought to tell you all what is happening as you were all so generous in your efforts to raise money for the Tsunami victims back in January.
Talk to you all on my return.
Colin
PS My Secretary is under instruction that her main task while I’m away is the securing of the Cuban Mahogany bench tops!
PPS Lance, I'll try to upload that MP3 before I go.Colin S38450.2318055556
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(anyone hear about the guy on vacation that rode the white water from the tsunami into the hotel restraunt where he was staying?)