‘Efficacy of Indian Early Tsunami Warning System proved'

The city-based Indian National Centre for Ocean Information Services (INCOIS), which ruled out a tsunami threat for the Indian Ocean on Friday, reconfirmed on Saturday that the sea levels in the Indian Ocean were not different from what had been anticipated.

INCOIS issued the first bulletin just seven minutes after the massive undersea quake near the east coast of Honshu in Japan on Friday.

The Indian Early Tsunami Warning System based on the data it received from seismic stations, sea level gauges, bottom pressure recorders (tsunami buoys) and the numerical model to predict the water level changes expected at various locations along the Indian coast worked well, a release from INCOIS said.

It reported that following the main shock on Friday till 9 a.m. on Saturday, about 130 aftershocks of more than 6.0 magnitude were recorded.

In fact, the first bulletin issued at 11.24 a.m. predicted the estimated magnitude of the quake in Honshu at 7.9 Mwp, and the estimated focal depth was 10 km. This matched with the initial magnitudes reported by other centres such as USGS.

Subsequently, on the arrival of more data from seismic stations, the magnitude was re-estimated at magnitude 8.6 and focal depth 5 km. This information was issued through the second bulletin at 12.15 p.m. Both the bulletins indicated that the India Ocean did not face a tsunami threat.

Both the bulletins were disseminated to the relevant departments in the Centre such as the Ministry of Earth Sciences, the National Disaster Management Authority, and other regional contacts.

INCOIS has 22 sea-level gauges at Aerial Bay, Chennai, Ennore, Garden Reach, Haldia, Kandla, Karwar, Krishnapatnam, Marmagao, Machilipatnam, Nagapattinam, Paradeep, Port Blair, Vadinar, Visakhapatnam, among others, and three bottom pressure recorders. Two such recorders in the Arabian Sea and the Bay of Bengal got triggered to tsunami mode due to the arrival of seismic waves.

In addition to the Indian systems, INCOIS also accessed the data in real-time, near real-time from similar observing systems maintained by other countries in the Indian and Pacific Ocean to follow the progress of the tsunami wave.

The model simulations done by the centre based on the data it received from its feeding stations, and the observed wave heights were comparable with the model estimates, the release said.

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Printable version | Sep 27, 2021 10:21:34 AM |

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