An instrument at the ocean bottom connected to the land by a cable
that provides power
for the measurement and transmission of data
from the seafloor to the coast.
Cables can extend for tens of kilometres offshore
and across oceans. They enable real-time,
multi-sensor seafloor
observatories to be deployed for
long-term monitoring. Examples of sensors on cabled systems
are seismometers to measure earthquakes, sensitive pressure gauges
to measure tsunamis, geodetic sensors
to measure seafloor deformation, and cameras.
Japan operates several
cable bottom pressure recording system
capable of detecting tsunamison
the order of centimetres, and a moored
surface buoy for real-time communications. An acoustic link is used to
transmit data from the seafloor to the surface buoy.
The data are then relayed
via a satellite link to
ground stations, where signals are demodulated, for immediate
dissemination to the NOAA tsunami warnings centres. The DART® data,
along with state-of-the-art numerical modelling capabilities, are part
of a tsunami forecasting system
package that provides predictions of tsunami impact
along site-specific coasts.
Schematic diagram of cabled ocean
system for monitoring earthquakes and tsunamis. Courtesy of Japan
Meteorological Agency.
