Indian Ocean Tsunami Warning System

The IOTWS is being built as a permanent system, informed by a number of Indian Ocean national tsunami warning centres, and by advice from Warning Centres from beyond the Indian Ocean. Nations will take responsibility for the issuance of warnings based on such advice

The IOTWS will comprise an interoperable system of interconnected networks and capabilities coordinated by the ICG/IOTWS and include:

• A basin-wide network of island and coastal tide gauges for confirmation (or denial) of tsunami and to provide direct evidence on the magnitude. They will also provide data for testing and validating models, both in scenario-building mode and as forecasts/hindcasts. For critical sites, data will be collected at at least 1 minute intervals and transmitted in real-time (e.g., 15 minute blocks), perhaps with options to transmit more rapidly in times of threat.
• A targeted network of deep-sea pressure measuring DART-like moorings (tsunameters), mostly located off the Sumatran Trench in the eastern Indian Ocean and around the Makran source in the Arabian Sea. Total numbers are likely to be in the range 10-16. Systems will typical transmit in 1 hour blocks and be triggered into real-time links when major perturbations are detected.
• Ocean forecast models, initialized by sea floor perturbations estimated from seismic data and (usually) constrained by assimilated ocean pressure and sea level data. There will usually be open-ocean models and coastal embedded models, perhaps down to fine scales for inundation forecasts. These same models would also be used to construct scenarios and a subset of the scenarios will be selected based on the observations.
• Vulnerability and risk assessment models where the risks to human life, the built environment and the natural environment are assessed based on possible tsunami scenarios. The IOC Assessment process will be important for setting priorities in this area.
• A system of Centres, equipped and operated by a subset of the Indian ocean nations and with a level of capability in most if not all of the areas listed above. These Centres will generated alerts, advisories and warnings within their jurisdiction and, as agreed, for others. National Centres will have varying capabilities but will formally have the responsibility for issuing and canceling warnings for their nation, based on advice from the above and elsewhere.