Scientists in Kolkata claimed to have moved an inch closer in predicting earthquakes - a feat that till date remained a dream for seismologists but could go a long way in saving thousands of lives every year across the world.
Here’s how. Earth based transmitters send out radio signals to communicate with submarines hundreds or thousands of miles away across the globe. The Ionosphere - a layer of the atmosphere located nearly 80 km above the sea level - reflects these signals back to us and helps in this communication process much like the way in which optical fibre works.
But astrophysicists at the Indian Centre for Space Physics (ICSP) near Garia in south Kolkata - a premier research institute aided by both the state and union government - over the past few years have been detecting certain anomalies in these reflected radio signals at least one to three days before any major earthquake in surrounding areas.
As of now even though meteorologists have managed to predict natural calamities such as cyclones and tsunamis and save lives, experts had no technique that could help them predict earthquakes. But if the claim of these city scientists holds true then it can save thousands of lives every year and avoid tragedies like that of Bhuj which claimed more than 13,000 lives in 2001, the Sumatran earthquake of December 26, 2004 which triggered the Tsunami claiming more than two lakh people or the Sikkim earthquake of 2011 that killed more."We have received at least two types of anomalies in these radio signals which are reflected back to us. While the first anomaly was detected at least three days in advance during the night, the second one comes a day before the quake during sunrise and sunset," said Sandip K. Chakrabarti, in-charge of ICSP and head of the Astronomy and Cosmology department at the SN Bose National Centre for Basic Sciences.
The results have recently been published in the Indian Journal of Physics in its October 2014 issue and a few other European science journals.
Way back in 1995 M Hayakawa a Japanese scientist had claimed of similar anomalies in radio signals just before the Kobe earthquake that shook Japan in January 1995 killing more than 6000 people. Taking a cue from that, Chakrabarti and his team at ICSP started measuring Very Low Frequency radio signals that are sent out by transmitters and reflected back to the earth by the Ionosphere.
The results showed that before any major earthquake (measuring more than 5 on the Richer Scale) the amplitude of these VLF radio signals fluctuate abnormally during the night at least three days before the tremors. “While under normal circumstances the amplitude is just two decibels, it goes up to 40-50 decibels three days before an earthquake,” he added.
“Our readings were corroborated by all the earthquakes be it 2004 Sumatran earthquake which later triggered the tsunami, the 2011 Pakistan earthquake that measured 7.2 on the Richter scale or the Japanese earthquake in the same year. We got signals in all the three and many more earthquakes including the one that shook Sikkim in 2011,” he added.
They have spotted yet another interesting phenomenon. Usually VLF-waves attain the minimum amplitude during sunrise and sunset. But just a day before the earthquake scientists have spotted that these VLF waves attain the minimum amplitude not at the time of sunrise or sunset but a few minutes before and after. Now that the scientists can claim to predict the approximate time when the next major earthquake will hit, the question arises: where will it hit?
Chakrabarti said: “For this we need to install a network of VLF radio transmitters and receivers at several key points of the country. After analyzing these simultaneously received data from all these stations in real time, we may be able to locate the area where the epicenter is.”
Scientists claimed that a possible explanation behind this phenomenon could be the increased activity of radon - a radioactive material beneath the earth’s surface - before earthquakes. These radons emit X-rays, which sets off a complex chain reaction in the atmosphere, which in turn affect the VLF waves reflected by the ionosphere which are received by the scientists.