Jan. 1: Scientists in the US have cautioned Delhi that aftershocks of last Sunday's earthquake off Sumatra are moving northwards and could potentially trigger a major quake in Assam.
Scientists at the Center for Earth Observing and Space Research at George Mason University in Virginia, who have been analysing seismic data since December 26, found the aftershocks moving north.
'If the sequence of these aftershocks moves further north, then it may trigger a very big earthquake in the Assam region, which is expected by scientists since long,' Ramesh P. Singh, a member of the Virginia team and vice-chairman of the International Union of Geodesy and Geophysics (Lugg) Risk Commission, told PTI.
'I hope it will subside. I am just alerting government agencies,' he said.
Assam home commissioner B.K. Gohain said the state government had not been informed of any such development. 'We are totally in the dark,' he said on being told about the scientists' observations. 'I'll have to ascertain this.'
Since last night, a series of tremors ranging between 5.0 and 6.3 on the Richter scale were recorded in the region from the Andaman and Nicobar Islands to Sumatra, raising the number of aftershocks to over 80.
Two tremors of moderate intensity occurred near Car Nicobar and two more near Great Nicobar, the Indian Meteorological Department (IMD) said in Delhi. The strongest measured 6.3 and was recorded at 11.56 am today to the west of Great Nicobar.
Seismologists said a quake occurred today under the sea off Sumatra. Its magnitude was variously recorded as 5.4, 6.5 and 7.0.
The Hong Kong observatory reported a 'severe earthquake' of 6.5 at 6.22 am GMT (11.52 am IST) today, 350 km west of Banda Aceh, close to the epicentre of last Sunday's tremor.
The State Seismological Bureau of China, however, said the tremor measured 7.0, Xinhua news agency reported.
The US Geological Survey's website said the quake measured 6.5 while Thai seismologists put it at 5.4.
Another measuring 3.58 jolted southern Bangladesh today at 12.02 IST, the country's official news agency BSS said.
A mild quake was also reported on the Bengal-Orissa border today. 'We have received an initial report from Digha that a tremor of slight intensity was felt between 6.05 pm and 6.06 pm,' a spokesman of the IMD's seismology section told PTI in Calcutta.
The Met department in Delhi said the tremor measured 4.4.
Assam has a GPS satellite network, set up by India's department of science and technology, to monitor crustal movements. Most of the state lies on the Dauki fault line, the junction of two pieces of the Indian tectonic plate, near what is known as the Shillong plateau.
Assam and the rest of the Northeast had suffered the 'Independence Day earthquake' of 8.6 magnitude in 1950 ' the sixth largest in the last century ' that killed 1,500 people.