The chances of increased seismic activities or even a tsunami-like event could be on the cards, east of northern Andhra Pradesh. When and if at all such an event occurs will be determined by a recently discovered fracture line under the Bay of Bengal.
This comes after a research team from the University of Hyderabad (UoH), in collaboration with National Institute of Oceanography (NIO) and Oil and Natural Gas Corporation Ltd (ONGC) uncovered the presence of the once active fracture line. It has a maximum activity focussed in the vicinity of offshore Visakhapatnam.
The researchers said the fracture line may possibly become active in future and result in a major coastal hazardous event associated with seismicity and tsunami in and around the Visakhapatnam region.
A continental collision that occurred between India and Asia around 40 million years ago led to the formation of the Himalayas, which in turn was responsible for major changes in regional and global climatic conditions.
Interactions between the Himalayas and the Asian climate initiated erosional process in the Himalayan and Tibetan regions. River systems carried copious amounts of material to the Bay of Bengal with a thickness reaching 22 km in the Bengal offshore basin. This huge sediment load had its mechanical impact on the eastern margin of India.
The research team of Prof. K.S. Krishna and Dr M. Ismaiel from the UoH, Dr K. Srinivas from the NIO and Dr D. Saha from the ONGC analysed seismic reflection data to address a cause-effect relationship between the sediment load and response of underneath heterogeneous igneous rocks in the Bay of Bengal.
They found the presence of a 300-km fracture line offshore of north AP and about 100 km away from the coastline.
“The study revealed that the fracture line had recorded a cumulative displacement of about 900 metre between the igneous basement and about 16 million-year-old sedimentary horizon. The fracture was reactivated 6.8 million years ago and continued the activity progressively until 0.3 million years before cessation,” Prof Krishna told Deccan Chronicle.
Excessive vertical throws (106 and 342 metres) occurred at the ages of 16 and 6.8 million years ago over a distance of 300 km offshore of north AP and may have prompted the generation of intensive tsunami events.
The fracture line may become active whenever differential stresses on either side cross the threshold level and may turn out to be a geohazard event. Its timing is not easy to predict, but will recur in a short time in the geological sense.
