Detection
With the huge Tsunamis in Hilo, Alaska, and the recent incident in south-east Asia, we are always looking for a sign that another is coming.
We have had tsunami detection for a while. The D.A.R.T (Deep-Ocean Assessment and Reporting of Tsunamis) was first being created and prototyped in 1995 and was deployed into the water in the year 2000. It consists of a buoy and a BPR (bottom pressure recording) that is attached to the ocean floor. The buoys last for about a year and the BPR’s last two, but by the year 2004 the DART systems have had a 96% data return cumulatively.
One of the things that gives it this good track record is the amount of functions each component can do. The BPR is a large box-like unit that sits at the bottom of the ocean. It is held down by a 720 pound anchor and holds down four of the main components: the bottom pressure recorder, the sensor, the transducer, and the processor/computer. Floating in the water, attached to the BPR is a rotating glass ball floatation that measures current and a signal flag so the recovery team can find it. The entire contraption goes 75 meters up from the ocean floor.
The buoy is held down by a 6850 pound anchor and attached to the buoy with a series of chain and nylon. The buoy has two antennas that direct to the satellite, two GPS antennas, so boaters can see where it is, and an RF antenna and RF modem. All of it is controlled by a master control system on the, which is 2.5 meters below the rest of the buoy.
The BPR collects information and relays it to the buoy. The buoy then sends signals to the main station through a satellite.
Click the above illustration to see a Flash animation of the DART process
Illustration and animation courtesy of NOAA ( National Oceanic and Atmospheric Administration )