Tsunami Warning Systems Efficient use of Tide Gauge Stations

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Tsunami Warning Systems Efficient use of Tide
Gauge Stations

• I.V. Fine1,2, F.E. Stephenson3,
• A.B. Rabinovich1,4 and R.E. Thomson1

1 Institute of Ocean Sciences, Sidney, B.C.
Canada 2 Heat and Mass Transfer Institute, Minsk,
Belarus 3 Canadian Hydrographic Service, Sidney,
B.C. Canada 4 P.P. Shirshov Institute of
Oceanology, Moscow, Russia
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The Sumatra-Andaman Tsunami of December 26, 2004
(Mw 9.3)
Deaths in South Asia could have been avoided
Beach of Krabi, Thailand
Phuket, Thailand (Photo by Ernesto Rodriguez)
No warning, no general knowledge about tsunamis
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The Sumatra-Andaman Tsunami of December 26, 2004
(Mw 9.3)
Phuket, Thailand (Photos by Helmut Issels)
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The Sumatra-Andaman Tsunami of December 26, 2004
(Mw 9.3)
Phi Phi Island (Photos by J.T. and Carolina
Malatesta)
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As a result of the Sumatra-Andaman Tsunami

• There has been a strong international commitment
  to install or upgrade many tide stations and
  seismic stations.
• This is an excellent start, but what can we learn
  from past experiences?

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What will this new network of tide gauges look
like in 30-40 years?

• What does past experience teach us?
• Canadian Arctic
• GLOSS program in the Indian Ocean

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In all probability

• Disaster response funding will be used to
  install many instruments and related
  communication systems
• Many nations / agencies will lack the means or
  the commitments to maintain these networks in the
  long-term
• The ability of these networks to provide
  effective tsunami warning will decrease

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An alternate strategy

• Before installing new coastal stations and
  offshore buoys, try to assess the hazards and the
  warning requirements
• Plan the network of stations to provide the
  required warning times
• Implement a network which is sustainable

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Tsunami Detection and Warning
For an arbitrary tsunami source location, we can
estimate a safe warning time (DT) -- for any
specified coastal site and known warning station
as the time delay between the arrival time at
the station and the coastal site
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Tsunami sources in the Indian Ocean (416 AD-2005)
Most of tsunami source regions in the Indian
Ocean are along the Sunda Trench subduction zone
(along Burma, Andaman and Nicobar islands,
Sumatra and Java). However, there are sources
(e.g. 1945) in the NW part of the ocean (Murray
Ridge)
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General seismicity of the Indian Ocean
416 AD - 2005
(courtesy of V.K. Gusiakov 2005)
The main seismic area is the extensive subduction
zone near the NE margin of the Indian Ocean.
However, there are also other zones the SW,
Central, Carlsberg and Murrey ridges
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Catastrophic tsunamis in the Indian Ocean
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Indian Ocean tide gauges for tsunami warning
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UHSCL stations that recorded the tsunami of
December 26, 2004
Australian station
Data from the GLOSS stations are still not
available
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Sea level records of the December 26, 2004
tsunami in the Indian Ocean
West Indian Ocean
Central and East Indian Ocean
All widely available records of the December 26,
2004 tsunami in the Indian Ocean are from UHSLC,
South African and Austarlian stations. The GLOSS
data are still not available
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Tsunami Detection and Warning
For an arbitrary tsunami source location, we can
estimate a safe warning time (DT) -- for any
specified coastal site and known warning station
as the time delay between the arrival time at
the station and the coastal site
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Delay (minutes) between a Nicobar warning
station and the City of Vishakhapatnam
A Nicobar site would provide an optimal warning
time (gt 2 hours) for a tsunami source located in
the SE Indian Ocean (similar to the Dec. 26, 2004
earthquake). However, such a site would not be
optimal for tsunami sources located in the West
Indian Ocean.
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Delay (minutes) between an Andaman warning
station and the City of Vishakhapatnam
An Andaman site would provide a less optimal
warning time (about 1.5 hrs) for sources in the
SE Indian Ocean compared with a Nicobar site,
but would improve warning time (gt 2 hrs) for
sources in the eastern part of the Indian Ocean.
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Delay (minutes) between a Minicoy warning
station and the City of Vishakhapatnam
A Minicoy site would provide excellent warning
time (2-4 hrs) for sources in the West Indian
Ocean but poor warning for sources in the SE
Indian Ocean (such as the Dec. 26, 2004
earthquake).
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Delay (minutes) for Vishakhapatnam for all three
warning stations combined
Simultaneous operation of all three warning
stations would remarkably improve the safety
(time delay) for Vishakhapatnam. Distant waves,
excluding those that came from the south, would
be recorded 2-4 hours prior to the arrival of the
waves.
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Delay (minutes) between a Nikobar warning
station and Phuket (Thailand)
A Nicobar site would provide an optimal warning
time (gt 1.5 hours) for a tsunami source located
off the western coast of Sumatra (similar to the
Dec. 26, 2004 earthquake) and for West, North,
and SE Indian Ocean. However, such a site would
not be useful for tsunami sources located between
the Nicobar/Andaman Islands and the maincoast (in
the Strait of Malacca)
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Delay (minutes) between an Andaman warning
station and Phuket (Thailand)
An Andaman site will provide better warning
time (gt 2.0 hours) than a Nicobar site for a
tsunami source located in the northern part of
the Andaman Sea, but will be much less useful for
a wave source near Sumatra (similar to the Dec.
26, 2004 earthquake). Such a site would also not
be useful for tsunami sources located between the
Nicobar/Andaman Islands and the coast of Thailand
(in the Strait of Malacca)
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Delay (minutes) between an open ocean warning
station and Phuket (Thailand)
An open ocean station deployed in the Strait of
Malacca between Nicobar Islands and Phuket would
significantly improve the situation for sources
located between the Nicobar/ Andaman Islands and
the mainland coast (Malacca Peninsula). It would
provide warning times gt 1 hour.
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Effectiveness of four warning stations (Male,
Gan, Diego Garcia and Cocos) for the coast of Sri
Lanka
The four stations will be highly effective for
the sources located in the West, South and SE
Indian Ocean (warning time gt 2 hours). Cocos
station also will be effective for a local source
offshore from SW and Western Sumatra. However,
these stations will not be effective for sources
located near NW Sumatra (similar to the Dec. 26,
2004 earthquake) and in the Andaman Sea.
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Effectiveness of five warning stations (Nikobar,
Male, Gan, Diego Garcia and Cocos) for the Sri
Lanka
An additional station (Nicobar) will greatly
improve warnings for the case of a local source
located near Sumatra (similar to the Dec. 26,
2004 earthquake) and in the Andaman Sea.
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Effectiveness of 4 warning stations (Male, Gan,
Diego Garcia and Cocos) for the coast of East
Africa
The four stations will be highly effective for
the entire east coast of Africa, providing
warning times gt 5-7 hours for sources in the East
Indian Ocean
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Some examples for Chile
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Several scenarios for Valparaiso
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Conclusions

• Modeling can be used to provide useful
  information on safe warning times
• This supports decision making about the optimum
  placement of gauges
• The effect of inoperative stations can be
  immediately accessed
• Time delays for data transmission can also be
  modeled

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Conclusions

• An efficient Tsunami Warning System is extremely
  important for the Indian Ocean

• International coordination, cooperation and
  data-sharing are crucial for an effective warning
  system. This is not a go it alone problem!

• A global network of tide gauges should form the
  backbone of the warning system.

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• Existing and newly-deployed open ocean island
  tide gauges will be effective for early tsunami
  warning for most countries in the Indian Ocean
  (including India, Sri Lanka, East Africa, and
  Madagascar).

• Additional buoys or bottom pressure gauges at
  open ocean stations are important for early
  tsunami warning for countries close to tsunami
  source zones (Thailand, Indonesia, Myanmar,
  Malaysia).

• Seismically-based early warning is important for
  regions located in the source regions (Sumatra,
  Nicobar and Andaman Islands).

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