The earthquake of 1.8 Richter scale, that occurred about 10 km off the coast of Visakhapatnam at a depth of 5 km in the sea, has surprised the scientific community in Andhra University, National Institute of Oceanography (NIO) and the Geological Survey of India (GSI).
What is even more surprising is that many of the residents had felt the tremors associated with a deafening blast-like sound, which is baffling the geophysicists.
An earthquake of 1.8 magnitude on the Richter scale, is not a significant event. As up to 3 on the scale is considered to be normal phenomenon, when it comes to tectonic activities, but what is surprising is the area of occurrence, felt the scientists.
Visakhapatnam is known to be a stable area when it comes to tectonic activities and this was for the first time that it has occurred so near to the coast, said Rama Rao, geophysicist from the Department of Bay of Bengal Studies, Andhra University.
According to the senior scientists in the GSI, the quake can be ignored in normal circumstances, but it occurring in shallow region of the ocean and so close to the coast, needs to be investigated and studied. And what is even more mysterious is the sound that the people had heard.
It is true that it had occurred in shallow region and that is why the propagation of the shock had travelled to a larger distance. But why it had happened needs to be studied, since there are not fault lines in the near vicinity, said K.S. Krishna from University of Hyderabad.
Many say that it could be due to differential compaction, because of sediment accumulation. But even that needs to be checked, said Rajsekhar Reddy, convenor INTACH and former professor Department of Geology, AU.
Acquiescing with Prof. Krishna, the geophysicist from AU pointed out that it could due a minor adjustment of rocks in the sub-surface below the ocean. But the sound was mystifying, as there was not thunderstorm activity during that period and it cannot be coincidental. Moreover, the water in the ocean mutes the sound, he said.
The epicentre is just 10 km away from the coast and the continental shelf is at least 50 to 60 km ahead, even that cannot be correlated, said the GSI scientists.
All are of the opinion that a study would clear the mystery, so that precautions if required can be taken.
