The Department of Atomic Energy is planning to use its captive seismic network for predicting tsunamis in the Indian ocean. The network was originally set up decades ago to detect underground nuclear tests from around the globe, especially India's neighbours, China and Pakistan.
The network is not very busy these days as nations have stopped nuclear testing. Besides, over the years, DAE has upgraded the network to a level that can predict whether an earthquake can cause a tsunami or not.
DAE seismologists K J Nair and Falguni Roy gave details of their 'real time seismic monitoring and tsunami alert system' at an international conference held in Kalpakkam during August 29-September 2.
"To provide a quick tsunami alert from a strong under-sea earthquake, one requires a seismic sensor network with enough aperture, real time data acquisition system, a satellite-based communication system and a data center where the data is collated and processed in real time," they told the conference. "The DAE has such a real time seismic monitoring and alert system at the Bhabha Atomic Research Centre."
Asked to elaborate, Nair, who heads the BARC seismology division, said, "BARC has capability for tsunami modelling using empirical decay curves and numerical methods to estimate the expected tsunami heights at depths of 1-4 km away from the shore. Once this information is available, the run-up calculation (to estimate wave heights at landfall) has to be used, which is site specific."
Traditionally BARC has been secretive about its in-house seismic network and the data it collects from around the world. It is not known to have had an open system of data exchange even with the Indian Meteorological Department. The misery caused by last year's tsunami appears to have caused a shift in the policy, prompting scientists to upgrade
the system for tsunami warning.
In the wake of last year's tsunami, the Science Ministry pledged Rs 120 crore for setting up a national tsunami alert system. It is not known if the ministry took into calculation the existing resource at BARC or how the two systems will be integrated. According to Nair, the two systems may exist side-by-side, complementing each other.
"The purpose of the BARC system is for building in-house capability for providing alert for such disasters," he told PTI. "The data from national tsunami warning system, when it will be available, will also be used for making its own disaster management decisions."
BARC's impressive seismic array at Gauribidanur, 120-km north of Bangalore is one of the world's biggest. The L- shaped array - with each arm 25-km long - has 20 seismometers embedded in rock, which BARC says 'can detect events of magnitude as small as 3.3.from SUNDA trench', the origin of last year's tsunami.
"This array has progressively undergone technology and data processing changes over the past decade and has in-house developed hardware and software needed for the real time data acquisition and processing," BARC scientists told the conference.
This, together with a seismic station in Mumbai and another seismic array in Delhi and a hook-up via India's INSAT-3C satellite to the data centre in BARC, complete the alert system.
An under-sea earthquake may cause a tsunami if it is strong and occurs at a shallow depth. It also depends on the vertical displacement at the fault and height of water column above.
BARC scientists said softwares like genetic algorithm (to estimate the location), artificial neural network method (for determining fault plane) and another novel method for estimating the source depth - all developed in-house - enable accurate values for each of these parameters within a short time.
"Once all the relevant parameters are estimated, together they will be able to indicate whether an earthquake would cause tsunami or not," the scientists told the meet. The ANN-based method is designed to mimic the pattern recognition process of the human brain. This method has been well established by BARC for earthquakes of Sumatra region.
"ANN can be used for classification of fault mechanisms of the earthquakes and from the type of fault mechanism, one can get a fairly good insight into the expected tsunami heights at the source. This is a scientific suggestion," Nair said.
He said the BARC system would provide the primary first information about earthquakes that will cause tsunami. "Additional wave height measurements will be needed for physical confirmation about the prediction," he added.
The BARC alert will be issued at three levels. Level three escalation is issued when seismic analysis of the event by many national and international centers also points to a hazard potential as high as estimated by the DAE network.
