| By and large, the administrations of several nations coped. People were moved out and, just as creditably, returned home, once the alerts were withdrawn, without civil disorder. |
| This was one useful outcome of the Sumatra quake: it showed that the nations hit on December 26 have developed rough-and-ready warning-evacuation systems that will limit damage from future tsunamis. |
| A basic tsunami warning system (TWS) for the Indian Ocean was scheduled to begin service on April 1, but it made its debut early. Warnings were relayed from Japan and the US. |
| A full-fledged Indian Ocean TWS is expected to go into service only in 2006. |
| The false alarm proved that, given a little notice, Asian countries can clear high-risk areas. But the false alarm also makes one wonder how reliably tsunamis can be predicted and, if it's possible to improve lead-times since areas 500 km from the epicentre can be hit within half-an-hour. |
| Tsunamis are caused by undersea disturbances like earthquakes or volcanic eruptions. Earthquakes are easy to pick up. Seismographs can accurately locate and measure every little ripple. |
| But seismography cannot predict if an earthquake will trigger a tsunami. Every strong (Richter 7-plus) "seaquake" does not cause a tsunami "" it needs vertical seabed movement and other specifics of energy-dispersion for tsunamis to result. |
| A tsunami is a magnified version of what happens when a pebble is dropped in a bucket of water "" only, tsunami waves ripple out to span entire oceans. |
| The characteristic pattern is a wave sequence with a period of 15 to 90 minutes between successive peaks. |
| These waves travel fast, at over 800 kmph in open seas. In open waters, tsunamis are low, just 10 cm to a metre high. But as it hits a coastline, it slows down; successive waves reinforce each other and the peaks climb to 15-50 metres. |
| Tsunami prediction depends on wave-detection as close to epicentre as possible. This is done through the use of buoys carrying tide-gauges that measure rising water-levels. |
| Tide-station networks are crucial since early-stage tsunamis are difficult to distinguish from normal wave patterns through satellite-imaging and satellite-date cannot be modelled quickly enough to be useful in real-time. |
| Another very useful tool is the Deep Ocean Assessment and Reporting of Tsunamis (DART) network of pressure recorders. The DART recorders sit on ocean floors and measure tiny difference in water pressure. The information is relayed through satellites in real-time. |
| The Pacific Ocean with its volcanically active "ring of fire" possesses a good TWS. The premier agency is the US government's National Oceanographic and Atmospheric Administration (NOAA), which takes the lead along with its Japanese counterpart, to coordinate tsunami information to 26 Pacific-Rim nations. |
| The TWS has over 60 tide-stations and 30 seismic stations located across the Pacific. |
| It can confirm Pacific tsunamis very quickly. But given tsunami speeds, areas 500 km from the epicentre can be hit inside 30 minutes. So, "ring of fire" nations print tsunami evacuation maps in their telephone directories. |
| These maps pinpoint high-risk areas and help speed up evacuation within the local zone of 30 minutes radius from epicentre. Cell-phone-based Global Positioning Systems (GPS) can also help perform the same task of warning. |
| The Indian Ocean does not have a comparable TWS. Indian Ocean nations are dependent on warnings relayed from the Pacific TWS. Judgements are necessarily less accurate and due to lack of local tide-station networks, Indian Ocean tsunamis cannot be confirmed early enough to prevent local zone devastation. |
| Both the speed and accuracy of Indian Ocean tsunami prediction will increase once a system of DART buoys and tide-stations is put in place by 2006. |
| Even more than money though, such a TWS will require inter-government cooperation between agencies of several different nations. That may actually be a stumbling block. |
Explore Business Standard