Geoscience Reference
In-Depth Information
Fig. 6.5 Layout of station (DART II) for registering tsunamis in the open ocean. The figure is
taken from http://www.ndbc.noaa.gov/dart.shtml (see also Plate 9 in the Colour Plate Section on
page 317)
station consists of an anchored surface buoy and a bottom platform; information
is exchanged between them via an acoustic communication channel (Fig. 6.5).
The sensor on the platform measures the pressure, averaged over 15 s, with an
accuracy, corresponding to a 1 mm water column. The level of the natural long-
wave noise (without account of tides) in the deep-water part of the ocean is not high
(its root-mean-square value is
0 . 2 cm). This makes it possible to reliably single out
tsunamis of heights of merely 1 cm, when the ocean depth at the site of the sensor is
about 6,000 m. The surface buoy is equipped with a satellite system for data trans-
mission (GOES) to the respective Tsunami Warning Centers for Hawaii and
Alaska and, also to PMEL. At present, 43 DART stations are in operation. Informa-
tion can be found at the freely accessible site http://www.ndbc.noaa.gov/dart.shtml.
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