Tsunami Detection System
A tsunami wave in
deep water creates a small but measurable change in pressure that
will be maintained for as long as twenty minutes. By monitoring
any such changes, subsea detectors can be used to trigger an alarm
that sends a warning message to a buoy-mounted receiver on the surface.
The buoy, in turn, relays the message via a satellite data link
to a control centre that can issue a warning to vulnerable communities.
The Sonardyne system is
based on a Compatt 5 subsea transponder that uses the latest
Wideband acoustic signal technology to provide robust through
water communications in difficult acoustic conditions. Compatt
5s are used extensively in the oil and gas industry where
their reliability is regularly trusted for use on the most
complex construction survey projects.
The Compatt 5 may be deployed
in water up to seven thousand metres (more than four miles)
deep and it is fitted with a sensor that continuously monitors
water pressure, saving data every fifteen minutes. Because
a reliable early warning of a tsunami can only be obtained
close to the sea floor, the Compatt provides the essential
means of sending these readings up to the surface. Every
hour the Compatt converts the pressure readings into signals
which it transmits acoustically to the buoy on the surface.
The satellite communications
transceiver on the buoy then automatically forwards the
pressure readings to the tsunami monitoring agency ashore.
The system can also receive data from the central control
so that revised monitoring parameters can be downloaded
to the Compatt if required.
The Compatt is programmed
to anticipate continual changes in the pressure of the water
as these can be caused by influences such as tides, weather
conditions and temperature. As these changes can be predicted,
a deviation of as little as 3cm from the expected pattern
will switch the device into alert mode. This will cause
the Compatt to immediately transmit any data that has been
saved during the past hour to the surface. It will then
take pressure readings every fifteen seconds which it will
immediately send up to the buoy for transmission by satellite
to the monitoring organisation. As a result, the first warnings
of a tsunami occurring several thousand of miles away can
be issued within minutes.
The advantage in using Sonardyne's
system over those of other suppliers is that the system
is small and self contained and thus easy to deploy. Additionally,
the heart of the system, Compatt 5, is based on proprietary
technology and the firmware and software can be easily updated
and adjusted if necessary.
Modern battery technology
and Sonardyne's experience of power management techniques
make it possible for the tsunami detection unit to remain
in continuous monitoring mode on the seabed for up to four
years. At the end of that period, a unique acoustic code
is transmitted from a surface ship to the tsunami transponder.
A mechanism is then activated which releases the attached
ballast weight enabling the Compatt to float up to the surface.
It can then be quickly serviced and fitted with new batteries
so that it can be re-deployed to resume its watch for the
tsunamis that can cause such devastation and loss of life.
||Type 8141 Buoy
Transmit Source Level
(dB re 1 µPa @ 1m
|Receive Sensivity (dB re
||1,500 baud (>600 baud user payload)
|Sonardyne Messaging Service
||Accessed through communications interface
|Error Detection & Correction
||Advanced protocols to minimise data
loss and re-sends.
||RS232/485 (9,600–115,200 baud)
with hardware handshake
||585mm x 183mm
|Weight in Air / Water
||9.75kg / 5.26kg
|External power requirement
24-50 Volts dc
||Type 8106 Compatt
5 Seabed Tsunamimetre
||5,000 metres ( 7,000m option)
|Transmit Source Level (dB
re 1µPa @ 1m)
||187-197dB (3 Levels)
|Receive Sensitivity (dB
||85-120dB (4 Levels)
||1,500 baud (>600 baud user payload)
|Battery Life (Monitoring)
|Safe Working Release Load
||1103mm x 135mm
|Weight In Air / Water
||28.2kg / 14.2kg
||7,000 metres (4,000m option)