Unusual quake pattern 'alarming'

Experts said that more than 120 tremblors in Andamans was rare.

Experts said that there was "unusual earthquake pattern" in Andaman and Nicobar Islands with more than 120 tremblors recorded in the last one month releasing a large amount of seismic energy.

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This kind of unusual release of large energy is considered as "unusual events" and "is unheard of in the history of seismology," the seismologists from Bhabha Atomic Research Centre (BARC) and the Earth Sciences Department of Indian Institute of Technology (IIT) here on Friday.

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 major earthquake that measured 8.9 on the Richter scale in Sumatra Island in Indonesia triggering tsunamis that wrecked havoc in South and South-East Asia.

Of these events recorded at BARC's Gouribidanur station in Karnataka, over 33 events were above 5 on the Richter scale, they said adding, "this is unusual and alarming as 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 Himalayan range while the dip slip will create local disturbance, they said.

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