Every sea floor earth quake or sea floor volcanic eruption does not trigger a Tsunami. Considering the damage caused by the Tsunamis in the past, definitely Tsunami Early Warning Systems are necessary. Same time we can not afford to have false tsunami warnings as they are costly to the people and to the government initiating preventive actions. There are occasions where tsunami warnings were false. Though false warning is better than no warning, false tsunami warnings are to be minimized. A reliable Tsunami Early Warning System is necessary.
GeoForschungsZentrum Potsdam (GFZ), Alfred Wegener Institute for Polar and Marine Research (AWI), Federal Institute for Geosciences and Natural Resources (BGR), German Aerospace Center (DLR), GKSS Forschungszentrum Geesthacht, Deutsche Gesellschaft für Technische Zusammenarbeit (GTZ), Konsortium Deutsche Meeresforschung (KDM), Leibniz Institute of Marine Sciences (IFM-GEOMAR), United Nations University Institute for Environment and Human Security (UNU-EHS).
For a reliable tsunami early warning, sea level recordings must take place off the coast, in the deep ocean. At water depths of thousands of meters, a tsunami wave travels at several hundred km/hr, but is only some tens of centimetres high, and approximately one hundred kilometres long. Only when a tsunami wave reaches the coast or shallower waters, the wave develops into a massive wall of water several meters high. Detection of very slight sea level rise in the deep ocean reliably and precisely requires the use of bottom pressure sensors (BPS). These BPSs are installed on the seafloor, where they measure even any small sea level changes in the water column above. In this process, the weight of any additional water leads to minute pressure increases at the seafloor which are, nevertheless, reliably recorded by the PACT (Pressure-based Acoustically Coupled Tsunami detector ) bottom units, precision instruments built by Optimare in Bremerhaven.
A typical Tsunami Early Warning System:
Alfred Wegener Institute for Polar and Marine Research has successfully tested Pressure-based Acoustically Coupled Tsunami detector (PACT) for real-time detection of sea level rises in the deep ocean. PACT is capable of recording sea floor pressure every 15 seconds and uses an acoustic modem to transmit information called as telegram to a second modem which is connected to a buoy near the surface, sending the data via satellite to the warning centre.The tests were conducted this month, north of the Canary Islands. From depths below 3100 metres and over periods of several days, pressure data were transmitted repeatedly to the surface modem. It was observed that none of the data telegrams were lost, signifying an achievement towards setting up of a reliable tsunami early warning system.
Having been tested successfully, the new system will now be integrated into the GFZ-developed surface buoy and the entire early warning system. Further tests, scheduled for early next year in the Mediterranean, will investigate the transmission reliability under various weather conditions.
Anchoring of the PACT bottom unit during the RV Poseidon expedition 360, on 05 November 2007, north of the Canary Islands. The PACT bottom unit was deployed at 3100 meter.
The PACT system consists of a bottom unit (white sphere — right) and a surface unit (pressure casing on frame — right). The battery-driven bottom unit contains pressure sensors, an acoustic transmission modem, as well as a release unit and a relocation device, the latter facilitating post-operation instrument recovery. The surface unit contains the acoustic reception modem. Attached to the underside of the surface buoy, a cable connection enables data transmission to the warning center.
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