Early warning system for Tsunami in the Indian Ocean
Tsunami is a series of traveling waves of extremely long wavelength generated primarily by earthquake occurring below and near the ocean floor. Underwater volcanic eruptions and landslides can also generate tsunami. Though the return period of tsunami is infrequent, the destruction done by tsunami is widespread, in terms of life and property. The most devastating tsunami occurred in December, 2004 affected the coastal countries of the entire Indian Ocean. It became necessary to set up a system in India to monitor seismic activity and sea level to evaluate potentially tsunamigenic waves and disseminate tsunami alert or warning.
The project on “Establishment of National Early Warning System for Tsunami & Storm Surges in the Indian Ocean” was approved by the Government of India in October 2005 for implementation at a cost of Rs.125 Crores with the Ministry of Earth Sciences as the nodal ministry. The major participants in the Project are institutions under Ministry of Earth Sciences [Indian National Centre for Ocean Information Services (INCOIS), National Institute of Ocean Technology (NIOT), Project Directorate of Integrated Coastal and Marine Area Management (ICMAM), India Meteorology Department (IMD)], Department of Science and Technology [Survey of India (SOI)], Department of Space (Indian Space Research Organisation (ISRO) and National Remote Sensing Agency (NRSA)], and Council of Scientific and Industrial Research [National Institute of Oceanography (NIO) and National Geophysical Research Institute (NGRI)].
The entire national Early Warning System is targeted to be made operational by September 2007 after necessary testing and simulations. This Project has been identified by the Government of India as a thrust area in its basic agenda for 2005.
The system comprises of network of seismic stations, bottom pressure recorders, tidal stations, coastal radars, and automatic weather stations, receiving data from all these sensors in near time, mainly using INSAT satellite and integrating them through decision support system and issue alert or warning as appropriate.
In the vicinity of India, there are two tsunmaigenic zones, Andaman- Sumatra trench and the Makran coast. It is necessary to monitor seismic activity along these two areas. This has been planned by installing digital seismometers, GPS receivers, and strong motion accelerometers and real time communication links to estimate moment magnitude reliably. This will help to provide first level of advisory within minutes of earthquake occurrence.
The installation and interconnecting 17 broadband seismic stations and for real time communication of data to the Central Receiving Station (CRS) of India Meteorological Department at New Delhi and to the Parallel CRS at INCOIS, Hyderabad is envisaged to be completed by August 2006.
Monitoring Sea Level
The initial tsunami warning or alert is confirmed by monitoring sea level in deep sea as well as on coast. This is being implemented by installing bottom pressure recorders (BPRs) and tide gauges to monitor sea level changes. India is installing such bottom pressure recorders in both the Bay of Bengal (10) and in the Arabian Sea (2) at appropriate locations. Four BPR’s have been deployed by NIOT in the Bay of Bengal. Data from one buoy is successfully transmitting data to NIOT that is being received in real-time at INCOIS through VSAT connectivity. ISRO is working on the indigenous development of BPR’s.
50 Tide Gauges are planned to be installed as part of this network (36 by Survey of India and 14 by NIOT). Data from Six Tide stations installed by NIOT at Chennai, Kandla, Vizhinjam, Mangalore, Minnie Bay, and Rangath Bay is being received at NIOT and retransmitted to INCOIS through the VSAT. The data from eleven tide gauges is already being received at SOI, Dehradun by VSAT network established by ECIL. INCOIS has initiated actions to receive SOI Tide gauge from Dehradun to INCOIS in real-time through VSAT.
Enhancement of Ocean observations
Five Coastal Observing Radars and two Current Meter Moorings are planned to be installed. HF Radars have been successfully used to detect and measure the strength of Tsunami Surface signatures. One such radar has been installed near Chennai for experimental purposes.
Upper Ocean and Surface Met- Ocean data from 25 surface drifters (atmospheric pressure, winds, subsurface temperature, surface velocities), XBT Lines (for collecting Temperature Profiles), Moored Data buoys (Air Pressure, Air Temperature, Humidity, Wind Speed & Direction, SST, SSS), and 25 Automatic Weather Stations (Air Pressure, Air Temperature, Humidity, Wind Speed & Direction, Rainfall) are being acquired. Drifters and XBT are being implemented through NIO. Moored Buoy data is being received from NIOT through VSAT.
Creation of high resolution topography and bathymetry
Coastal topography and bathymetry play very crucial role in running inundation models. A very detailed survey of the Indian coastline has been initiated, wherever such information was lacking.
Bathymetry data base at appropriate resolution and format required for Tsunami and Storm Surge Models has been created using all the existing sources of data as well as by conducting surveys at selected critical coastal locations.
NRSA is responsible for Topographic Mapping of 15, 000 Sq km area (for 7500 line km and 2 km inland from the coastline) with airborne LIDAR & Digital Camera data in conjunction with GPS control survey using photogrammetric techniques. NRSA has already acquired required airborne data for Machilipatnam – Kochi stretch i.e. for an area of Kochi stretch i.e. for an area of 3,300 sq. km. Of this, processing DEM generation from Nagapattinam to Cuddalore has been completed. The generation of digital topographic maps for the balance 3040 sq km is progressing and this is expected to be completed by April – May 2007. The aerial flying for the remaining 11, 700 sq km, is under progress.
Coastal vulnerability modeling and inundation mapping
The information about magnitude, location, and depth at which an earthquake has occurred has been used to model travel time, inundation, and run-up of tsunami to coastal regions. Since running such models in real time is not advisable, it is necessary to generate scenarios (in thousands) of various possible earthquakes and generate look-up tables for possible travel time. A travel-time atlas has already been generated. The information about sea level can also provided to this model for validating earlier estimates of travel time, inundation levels, and run-up.
The possible risks of coastal inundation due to tsunami and storm surge by using tsunami and storm surge models constructed using numerical equations have been implemented. Inundation Maps of coastal locations have been generated by ICMAM on 1:4000 scale for 5 scenarios of historical Earthquakes and Storm Surges.
Setting up a dedicated early warning centre
An Interim Tsunami Warning Centre, following the Standard Operational Procedure, has already been made operational at INCOIS since July 2005. This centre receives earthquake and tsunami advisories from India Meteorological Department, Japan Meteorological Agency, Pacific Tsunami Warning Centre as well as Tide Gauge Data from SOI, NIOT and other International Stations. This arrangement has worked well during the Tsunami that hit Java on July 17,2006 wherein it was confirmed within an hour that the Tsunami was not likely to hit the Indian Coastline.
Communication of real-time data from Seismic Stations, Tide Gauges, BPR’s to the early warning centre is very critical for generating timely tsunami warnings. An end-to-end communication plan has been worked out in collaboration with the Indian Space Research Organisation that envisages use of INSAT DRT for one way and INSAT MSS for two way communication from Tide Gauges and DART Buoys. The installation of INSAT Satellite Communication facilities at INCOIS will be ready by March 2007. In addition, VSAT network, dedicated broadband internet and INMARSAT reception facilities are also being established.
The Virtual Private Network for Disaster Management Support (VPNDMS) node has been set up at INCOIS that facilitates reliable connectivity to the Ministry of Home Affairs for dissemination of Warnings. In addition, INCOIS is also working on technological options that facilitate dissemination of warnings directly to the public through Mass Media, IMD Cyclone Warning Centers, PFZ Electronic Display Boards, Mobile SMS Messages, Telephones, etc.
An easily understandable publicity material on earthquake, tsunami, and storm surges in vernacular languages is being created to be distributed to the general public. A dedicated multi-lingual web-site is also being developed to provide information on Tsunamis and Storm Surges.