JEDDAH, 5 January 2006 — The very fact that someone has predicted the occurrence of an earthquake should raise eyebrows in the thinking community. Along with “end of the world tomorrow-ists,” “millennium bug will destroy mankind-ists” and “buy this winning lottery ticket-ists,” anyone who claims to predict an earthquake with pinpoint accuracy is in danger of committing “shirk”.

When it comes to predicting earthquakes, God knows; we do not. Earthquake prediction is far from an exact science. It is a discipline that exemplifies Kierkegaard’s observation that “life is lived forwards but only understood backwards.”

According to Dr. Ian Stewart and Dr. John Roobol at the Saudi Geological Society, despite huge efforts over the last three decades or so, seismologists still cannot predict times or locations of earthquake with any degree of accuracy. Past events can only ever be a guide to future locations. As to when they will occur, at best seismologists have only a statistical idea of the frequency of occurrence.

This data is however useful in designing and building the infrastructure of a city in an earthquake zone. Stewart explained that by using the data collected by the seismic sensors it is possible to establish the probability of suffering a magnitude six earthquake, for example, within a specified period of time.

“We know earthquakes follow very well-defined statistics and we can work out the risk,” he said. “If you know that you are going to experience a ground acceleration rate of x centimeters per sec squared in 50 years, you can design buildings to allow for this.”

However good the statistics, pinpoint prediction of time and place is impossible. But there is, as in all tall tales, an element of veracity. Jeddah already gets a goodly number of tiny tremors or “seismic events” each year. Most of them are so small they go entirely unnoticed except by the extremely sensitive instruments at the Saudi Geological Society.

Late last year, a minor tremor hit Makkah, but it had no effect other than knocking as few loose bricks out of buildings. Jeddah is largely protected from earthquakes, even though it balances on the edge of the Arabian tectonic plate — a huge part of the earth’s relatively thin crust and a part that is constantly moving north-eastward about the same number of centimeters per year as your fingernails grow. The edge of a tectonic plate is usually a seismically active area and the west coast of the Kingdom is no exception.

It is therefore possible — not probable and certainly not definite — that a tiny tremor, which might technically be an earthquake if you want to describe it as that — will occur a long way under or about 80 km west of Jeddah in the Suakin Deep tomorrow. The Suakin Deep does have some really quite big ones.

However, even though Jeddah is on the edge of a tectonic plate and relatively near an earthquake zone, it has a huge and incredibly effective natural shock absorber.

Deep under the city and stretching hundreds of kilometers north and south is a thick layer of evaporate, salt by any other name. The evaporate layer is waterlogged and it stands between Jeddah and the earthquake zones. When even quite large tremors reach it, they are simply absorbed. So effective is it that the shock waves from seismic events of up to six on the Richter scale have been absorbed in the past. That kind of event would virtually destroy the city were it not for the evaporate layer. This is not to say that Jeddah will never suffer an earthquake; that is as idle a prediction as “earthquake tomorrow.” The best we can say is, “so far, so good.”

Now, which lottery ticket did you say it was?