Quakes: of prediction, coincidence and panic

Published in The Hindu on September 14, 2006

Earthquake - USGS
Very few students were present in schools on September 8 morning in Guwahati following the earthquake panic.– Photo: NASA

Next time when someone predicts an earthquake with great certainty and specifies the exact time, location and magnitude, take it with a pinch of salt. More so, if it is predicted to happen in a few days’ time.

A recent prediction by N. Venkatanathan who had done his Ph.D from the Department of Applied Geology, University of Madras, Chennai, not only indicated the location (epicentre about 15 km southwest of Dibrugarh in Assam) and magnitude of 7-8, but also the exact time. No earthquake happened on that day despite the 70 per cent possibility that he had predicted. But it surely created great panic and anxiety.

But an earthquake of magnitude 4 happened on September 10 at Manipur-Myanmar region. “I had given a window period of three days for that earthquake,” said Venkatanathan. The conclusion – the prediction indeed was correct!

Question of magnitude

The magnitude was not; it was 1000-10,000 times smaller than the predicted 7-8 magnitude as the magnitude is measured on a logarithmic scale. His prediction can thus not be termed correct as it failed on this aspect. For an accurate prediction, the magnitude, time and location need to be correct.

A paper published by him and others last year in the Journal of Indian Geophysical Union states, “it is inferred that the magnitude of the tremor is related to the direction of planetary forces acting at any particular point.” Incidentally, a note given by him to this correspondent stated nothing about the direction of planetary forces and the resultant magnitude. It instead stated that the magnitude was arrived based on past earthquake data for the recent prediction! “Yes, the magnitude predicted was not correct,” Venkatanathan admitted “but did the seismologists not keep correcting the magnitude after the December 2004 earthquake?”

The reasoning falls flat as it is well known that the correct magnitude can be arrived at only when data from many stations are assessed, more so when the earthquake is of a high magnitude.

Still elusive

“Earthquake prediction is the Holy Grail of seismology. The ability to predict the time and location of earthquakes remains elusive… ” stated a paper published in Nature last year. According to Venkatanathan, the planetary alignment will cause a small `bulge’ on the earth at a microscale level. And this `bulge’ produces a change in the earth’s rotational speed, which in turn produces a change in the tectonic plate motion. “That triggers an earthquake if there is enough accumulated stress,” he underlined.

The bulging question

That the earth is an elastic body and it bulges under moon’s gravitational force is well known. “But the effect of other planets to produce such a bulge will be less than one hundredth of what the moon does,” underlined Prof. Vinod K. Gaur who is with the Indian Institute of Astrophysics, Bangalore.

So the moon and sun should be able to produce more quakes when one or more plantes get aligned with the earth. That the sun and moon alignment does not produce earthquakes is now well understood. About the change in the rotational speed, Prof. Gaur noted that the earth constantly undergoes wobbling on its axis and at various periodicities to produce changes in rotational speed. “The sun and moon should have greater effect than other planets [on the rotational speed],” underlined Prof. Gaur. Venkatanathan has no data to support the actual changes in the plate motion. “Even the Sumatra earthquake did not cause any change in the Indian plate velocity,” Prof. Gaur said.

If a major earthquake where the plate had fractured for about 1300 km in length failed to cause it, can just an alignment of planets produce it? If indeed the planetary alignment and the resultant forces can produce earthquakes, then May 5, 2000 should have produced major earthquakes measuring more than magnitude 7. “… No major earthquake was reported on that day! In fact, only 15 earthquakes with M [magnitude] 7 were reported in 2000, whereas the annual average of such earthquakes was around 19,” noted a correspondence published in Current Science last year. “It is not just alignment that matters,” he stressed, “there should be force change caused by change in distance between planets that are in elliptical orbits, and direction of planetary force to produce earthquakes.”

While the September 8 prediction went wrong, the United States Geological Society website has 20 earthquakes striking different parts of the earth the same day, including one in the Andaman Islands.

Quakes in other locations

Now, why did an alignment and other related forces required to produce earthquakes not cause one in Assam but caused quakes in places such as Japan, Hawaii, Tonga, Alaska, and Puerto Rico? Did these locations meet all the prerequisites as required by his hypothesis? “I am yet to analyse them,” he said.”There is no scientific theory developed to show a relationship between planetary alignment and earthquakes. These are just observations,” said Dr. R.K. Chadha, scientists with the National Geophysical Research Institute, Hyderabad.

With so many constraints, such as the earlier occurrence of faults in the region, temperature, isostatic pressure, properties of rocks (mechanical and chemical) and heterogeneity of rocks, earthquake prediction has been one of the toughest challenges explained Prof. Sharma of the Department of Earth Sciences, IIT Roorkee.”At present time, optimism is rather low about the prospects for short-term prediction,” noted another paper published in 1996 in the Proceedings of the National Academy of Sciences. And it still holds true.

The Parkfield section of the San Andreas Fault in California is one of most networked places on the earth to study earthquakes. The Nature paper noted, “… Lack of short-term precursors emphasises the difficulty of reliable short-term earthquake prediction (up to a few weeks before).” A host of parameters, including magnetic field, electric field but not planetary alignment and the forces they exert to produce earthquakes are being studied in Parkfield. “The extent to which earthquake phenomena can accurately be predicted will ultimately depend on how well the underlying physical conditions and processes are understood,” the Nature paper highlighted.

Never be possible

“This being a global phenomenon, pinpointing the location and exact time when an earthquake will occur will never be possible for the next 50-100 years,” said Dr. Chadha of NGRI. With many variables not studied and understood, and more data required, as Venkatanathan himself agrees, his hypothesis shall rest on coincidences based on cherry picked data. Nothing more.

And as Prof. Gaur noted, mere coincidence is no way of correlating the cause and effect. It will be wise to get the hypothesis published in reputed international peer-reviewed journals and accepted by the community before going to the public and alerting them of impending earthquakes.

It may well be remembered that many parameters thought to be precursors have not stood the test of scrutiny. In this case, it is projected as a triggering mechanism. And this makes it all the more difficult to come out successful.

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