The Hindu : National : `Unusual quake pattern' observed in Andamans

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Saturday, Jan 29, 2005

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National

`Unusual quake pattern' observed in Andamans

MUMBAI, JAN. 28. Experts today said there was an "unusual earthquake pattern" in the Andaman and Nicobar Islands with more than 120 temblors recorded in the last month, releasing a large amount of seismic energy.

This kind of unusual release of energy "is unheard of in the history of seismology," the seismologists from the Bhabha Atomic Research Centre and the Earth Sciences Department of Indian Institute of Technology here, said.

The Seismology Department of BARC and the Earth Sciences Department of IIT have recorded over 120 such "unusual events" in the islands following the December 26 earthquake that measured 8.9 on the Richter Scale in Sumatra in Indonesia triggering tsunamis that wreaked havoc in South and South-East Asia.

`Alarming'

Of these events, recorded at BARC's Gouribidanur station in Karnataka, more than 33 events were above 5 on the Richter Scale, they said.

"This is unusual and alarming as [a] large amount of energy is being released so frequently."

The earthquakes recorded had both `strike slip' (lateral movement) and `dip slip' (vertical movement).

The strike slip would put tremendous pressure on the Himalayan range while the dip slip would create local disturbance, they said.

Eleven events with surface wave of magnitude 5, indicating large amounts of energy close to the Nicobar Islands was also recorded, the seismologists said.

"Since yesterday, at least 16 temblors ranging from 5.2 to 5.8 on the Richter Scale were recorded," they said.

"Whether these events are foreshocks or aftershocks is not clear. It has to be taken up seriously and the data analysed as quickly as possible."

"Both `strike slip' and `dip slip' are taking place simultaneously and these factors have to be taken seriously both by scientists and authorities," they said.

PTI

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