Transcript Causes of Tsunamis

Understanding…
Tsunamis & Other Coastal Hazards Warning System Project
2010
Teacher Presentation
User’s Guide to Understanding Tsunamis Presentation
The “Understanding Tsunamis” presentation contains information on the science of
tsunamis, the Caribbean’s vulnerability to these events and tsunami safety tips. This
presentation is suitable for teachers, disaster management practitioners and any
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Understanding Tsunamis - Outline

Role of the Caribbean Disaster Emergency Management
Agency and the UWI Seismic Research Centre

Nature of tsunamis

Causes of tsunamis

Effects of tsunamis

Case studies

Preparedness
Role of the Caribbean
Disaster Emergency
Management Agency & the
UWI Seismic Research Centre
Caribbean Disaster
Emergency Management Agency
CDEMA is responsible for 18 Participating States in the
Caribbean, from Belize in the north-west to Suriname in the
South for which it:

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Mobilizes and coordinates disaster relief
Mitigates the immediate consequences of disasters
Provides immediate and coordinated disaster response
Provides reliable and comprehensive information on disasters
Champions disaster loss reduction and mitigation policies in the region
Fosters a culture of disaster loss reduction
Maintains adequate emergency disaster response capabilities
UWI Seismic Research Centre

Monitoring – Earthquakes, Volcanoes, Tsunamis

Mitigation – Providing contributing governments
with maps and information on
geologic hazards.

Education – Supporting disaster management
agencies with public education efforts.
Nature of Tsunamis
What are Tsunamis?

Definition

Misconceptions

Description
Tsunamis are:

Derived from 2 Japanese words
tsu (harbour) + nami (wave).

A series of ocean waves caused by an abrupt
disturbance of the ocean floor that displaces
a large mass of water.

Waves that radiate outward in all directions
from the disturbance that can propagate
across entire ocean basins.
Tsunamis are NOT tidal waves
 Tsunamis have erroneously
been called “tidal waves”.
 They have nothing to do with
the attraction of the Moon or
the Sun
 Use of the term is being
discouraged
The following animation demonstrates
the development and movement of
tsunamis
Tsunami Inundation - Animation 1
Tsunami terminology

Wavelength: the distance
from one crest of the
tsunami to the next.

Inundation: the maximum
distance inland from the
normal coastline reached
by the tsunami or
maximum area covered by
the water.

Run-up: maximum height
onshore reached by the
tsunami.
How do tsunamis behave?

Evolution of a tsunami

How they behave in deep ocean

How they behave as they approach the coast

How they behave when they reach the shore
Tsunamis evolve through 3 stages
3. INUNDATION
2. PROPOGATION
1. GENERATION
REFRACTION
Refraction and shoaling funnel the wave’s
energy into a dangerously high wall of water
SHOALING
In deep ocean
As tsunami waves cross the deep ocean:
 Their wavelengths may exceed 100km
 Their wave height will be about 1 metre
 Their speeds range 500 – 800Km/hr
 They cannot be felt aboard ships nor can they be
detected from the air.
 Ocean depth determines the velocity
Approaching the coast
Tsunami waves change as they leave the deep water of the open
ocean and move into shallow water near the coast, it changes.
Reaching the shore
 The water level on shore can increase by many metres.
 The first wave may not be the largest in the series of waves.
 One coastal area may see no damaging wave activity while in
another area destructive waves can be large and violent.
Causes of Tsunamis
What generates a tsunami?

Earthquakes
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Volcanoes

Tsunamis generated by Volcanic eruptions in the Caribbean
Submarine volcanoes

Submarine landslides

Cumbre Vieja tsunami potential


Plate tectonics
Plate tectonics in the Caribbean
How earthquakes generate tsunamis
Earthquake generated tsunamis in the Caribbean
Tele-tsunamis
Other possible causes – Asteroids/Meteorites
Earthquake-generated tsunamis
• Tsunamis are mainly
associated with earthquakes
occurring below or near the
ocean floor.
• This abrupt shift in the sea
floor shifts causing a sudden
displacement of the overlying
water.
• Waves form as this water
mass, under gravity, tries to
regain its equilibrium.
Earthquake generating tsunami - Animation 2
Image: Kious & Tilling, USGS. This Dynamic Earth: the Story of Plate Tectonics; Historical Perspective.
http://pubs.usgs.gov/gip/dynamic/historical.html
Plate tectonics setting of the Caribbean
Plate boundaries
 Convergent/ Subduction
(Lesser Antilles)
 Strike-slip (north and south)
 Divergent/ Sea-floor spreading
(Cayman Trough)
Defined by the distribution of
earthquake epicenters.
~ 1% of the world’s seismic
energy is released in the
Caribbean
Shallow earthquakes along
subduction zones, can
generate destructive tsunamis.
0 – 35km deep
35 – 100km deep
>100km deep
Do all earthquakes generate tsunamis? NO!

To generate a tsunami:


The fault where the
earthquake occurs must be
underneath or near the
ocean.
But more importantly:

A vertical movement (up to
several meters) of the sea
floor over a large area (up to
100,000km2) must be
created.
The size of the tsunami is determined by:
 Amount of vertical sea floor deformation
 Area over which it occurs
 Slumping of underwater sediments during the earthquake
 Efficiency of energy transfer from the earth’s crust to the
ocean water.
 Shallow focus earthquakes (depth <70km) of magnitude >6.5
along subduction zones are responsible for most destructive
tsunamis.
Types of tsunamis
1. Local tsunamis - generated by earthquake sources less than
100km away with very short travel time.
2. Regional tsunamis – generated by earthquakes within the
region with travel times within the range of 30 minutes to 2 hours
from source to coastline.
3. Tele-tsunamis - generated by earthquake sources outside of
the region with travel times of up to 24 hours before impacting
distant coastlines.
Potential for local earthquake-generated
tsunamis
 Approximately 40
earthquakes in just
under 500 years which
satisfy these criteria.
 With sufficiently high
magnitude (> 6.5)
 At sufficiently shallow
depth (< 50 km).
Actual tsunamigenic earthquakes
Date
Location
Cause
Mag Effects
1690 April 6
Leeward
Islands
Earthquake
between Antigua
and Guadeloupe
7.57.8
Separate tsunamis generated by landslides into the sea in Antigua and
Nevis. Extensive earthquake damage but no reported damage or casualties
attributed to tsunamis
1692 June 7
Jamaica Cuba
Earthquake
7.5
Tsunami generated with run-up of 1.8m. Of the 2-3000 casualties, most
were attributed to the earthquake.
1842 May 7
Hispaniola
Earthquake
8+
Tsunami waves generated on the north coast of Hispaniola. Reports claim
the sea receded 60 m and the returning wave covered the city of Port-dePaix, Haiti, with 5 m of water. About 200-300 lives were lost that day.
1867 Nov 18
Virgin Islands
Earthquake
between St.
Thomas and St.
Croix
7.5
Tsunami possibly generated by submarine landslide up to 8m high
generated in the Virgin islands causing 23 deaths. Travelled west to Puerto
Rico, east to Barbuda and south to Grenada
1907 Jan 14
Jamaica
Earthquake
6.5
Tsunamis triggered on the North coast of Jamaica possibly associated with
submarine landslides. Waves up to 2.5 m affected the North coast from Buff
Bay to St. Ann’s Bay and at Anotto Bay the sea reportedly receded up to 93
m.
1918 Oct 11
Puerto Rico
Earthquake
between Puerto
Rico and
Dominican
Republic
7.5
Tsunami up to 4m high generated on the west coast of Puerto Rico,
inundated 100m inland, causing 29 deaths and extensive damage. Noticed
on the east coast of Dominican Rep. and Virgin Isl.
1946 Aug 4
Dominican
Republic,
Hispaniola,
Virgin Islands
Earthquake near
Dominican
Republic
8+
Earthquake devastated the Dominican Republic, extending to the Virgin
Islands and Haiti triggered a 2.5 m tsunami that pounded the northeast
coast of Hispaniola. The greatest loss of life occurred at Mantanzas
(Matancitas) where one Disaster coordinator related “The tsunami wave
entered almost a kilometer inland, and swept the city and several villages
into the ocean.”
Tele-tsunamis
Tele-tsunamis are tsunamis generated outside the region which
enter the region through large ocean basins such as the Atlantic
Ocean.
Date
Location
Cause
Mag
Effects
1755 Nov 1
Eastern
Caribbean
Great Lisbon
Earthquake in the
Azores fracture
zone
8.7
Tsunami generated crossed the Atlantic and
was noticed throughout the region from
Barbados to Antigua and as far west as
Cuba. 2-10?m high waves were generated
and continued to arrive for many hour. No
damage or casualties reported
1929 Nov 18
Eastern
Caribbean
Earthquake off
the Grand banks
of Newfoundland
?
Reports suggest that tsunami reached
eastern Caribbean but damage assessment
unconfirmed
Institute of Computational Mathematics and Mathematical Geophysics
Siberian Division Russian Academy of Sciences
Tsunami travel time chart for the 1755 Lisbon tsunami. Solid ellipse marks position of the
earthquake source. Red color shows the area within 1-hour propagation time.
Tsunamis from volcanic eruptions
Volcanic eruptions may cause tsunamis in a number of ways - all impact the water to
create displacement of the ocean generating tsunami waves.
Pyroclastic flows
travelling over
the surface into
the ocean from
an eruption of
the Soufriere Hills
Volcano, on the
Island of
Montserrat.
Tar River Valley mud flow, Montserrat
(Photo courtesy Eroscilla Joseph SRC)
Volcanic tsunamis generated within the region
Date
Location
Cause
Effects
1902 May 7
Martinique
St. Vincent
Volcanic eruption
of Soufriere and
Mt. Pelee
Entry of pyroclastic flows into the sea in
St. Vincent created disturbances of the
sea with tsunami waves 2-3 m high in
Grenada, Barbados and St. Lucia. Reports
from harbormasters confirm the event.
Submarine telecommunication cables
from Martinique were cut that day
1997 Dec 26
Montserrat
Volcanic eruption
of Soufriere Hills
Major pyroclastic flow entering the sea in
southwestern Montserrat generated
minor tsunami confined to Montserrat
Tsunamis from submarine volcanic
eruptions
Kick ‘em Jenny
eruptions
generated
tsunamis:
Violent submarine volcanic eruptions can
create an impulsive force that uplifts the water
column and generates a tsunami.
July 24th 1939
Northern Grenada
Southern
Grenadines
Barbados
October 30th
1965
Submarine volcanic eruption off the coast of Tonga (March 2009)
Kick ‘em Jenny submarine volcano, Grenada
Kick ‘em Jenny has
generated at least 2
tsunamis since 1939
Kick ‘em Jenny
Tsunamis from submarine landslides

Largest tsunami
reported in the
Caribbean
Landslidegenerated
tsunami,
Northern coast
of Guadeloupe
Generated by
an earthquake
event in 1867.

These can occur when a tectonic trigger causes
the ocean floor to slump or when huge chunks
of glaciers, volcanoes or other debris slides
crash into the sea.
Since the source of landslides is near shore the warning time may be only a few minutes.
When the ocean bottom
crumbles in an
underwater landslide,
the moving material can
push water in front of it
and create a tsunami
wave.
Puerto Rico Trench Landslide Tsunami Time Travel Simulation - Animation 3
Landslide generating tele-tsunami potential:
Cumbre Vieja Volcano
 The Cumbre Vieja Volcano is an
active volcano located off the west
coast of Africa.
 Evidence suggests that a future
eruption may cause a catastrophic
failure of the sides of the volcano,
dropping large masses of rock into
the sea.
 Tsunami waves could be produced
travelling over the Atlantic Ocean
into the Eastern Caribbean with
wave heights of 10-20m.
La Palma Collapse Tsunami Time
Travel Simulation – Animation 4
Other possible causes of tsunamis
Artist impression

Cosmic-body impacts such as:
 Asteroids
 Meteorites
 Comets
can also disturb the water as falling
debris from above displaces the
water.

Evidence suggests that an impact on the
order of a 10-megaton explosion could
occur once every few hundred thousand
years!
Effects of Tsunamis
Why are tsunamis so dangerous?

Indian Ocean tsunami, December 2004

Enormous force of tsunamis
 Extent
of inundation and run-up
 Short film of tsunami footage
26th December, 2004 Indian Ocean Tsunami



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Magnitude 9.1 earthquake generated a tsunami
12 countries around the Indian Ocean impacted.
More than 230,000 fatalities
2.3 million people left homeless
Estimated property damage and economic loses were in the
tens of billions of dollars.
Photo Courtesy: Peter Lemieux
The force of tsunamis can be enormous



Powerful waves move dangerous debris (boats, cars, trees)
hundreds of metres inland.
Tsunami waves can destroy buildings
Moving water and debris can kill or injure people.
BEFORE
AFTER
Lhoknga, Sumatra January 2003
Lhoknga, Sumatra December 2004
Images Courtesy: Ikonos Satellite Image © CRISP, NUS (2003, 2004)
Impact of tsunamis

Visit this link online to view a short film of what
people experienced during the 2004 Indian Ocean
Tsunami on SRC You Tube channel:
http://www.youtube.com/user/UWISeismicResear
ch#p/f/5/RDOuwMj7Xzo
Preparedness and
Safety
What can we do?




Tsunami warning and preparedness
Tsunami natural warning signs/ Sensing a tsunami
What to expect in the event of a tsunami
Things to remember
 Before
 During
 After


Emergency preparedness
Knowledge and safety
Tsunami Warning and Preparedness
 All low-lying coastal areas can be struck by tsunamis.
 Travel times for damaging tsunamis are generally < 10 minutes.
 There may be insufficient time to issue warnings
 Preparedness for tsunamis should concentrate on identifying
tsunami natural warning signs.
Sensing a tsunami
• Tsunamis can sometimes be
detected by natural warning
signs using human senses.
FEEL
• Do you FEEL the ground
shaking so strongly that
standing is difficult?
Sensing a tsunami
SEE
• Do you SEE an unusual
withdrawal of the sea
exposing rocks, reefs or
fish?
HEAR
• Do you HEAR a strange
roar of the waves?
Sensing a tsunami
• Often the first
sign is an
Earthquake
• Followed by a
withdrawal of
the sea.
Sri Lanka, 26th December 2004
Image shows “drawback” or withdrawal of water exposing ~150 meters of temporary beach. Photo: www.digitalglobe.com
Then it returns like a wall of water
• Never go to the
beach to wait
and watch for a
tsunami.
• If you can see
the wave, you
are already too
close to outrun
it.

Remember there
are many waves
and the first
wave may NOT
be the last or
largest.
Remember
• If you

FEEL or
SEE or
HEAR a tsunami coming

RUN !!!!


• RUN for high ground as
fast as you can.
• Do not return to the
beach until the “AllClear” is issued by
authorities.
Before a tsunami
• Know how far you are from the coast
• Learn the quickest route to get to high ground
• Ensure that you and your family know how to detect tsunami
signs
• Have an emergency plan and emergency supplies
During a tsunami
• Have an emergency plan and emergency supplies.
• Tsunamis may occur without the initial pulling back of the
sea.
• If you cannot get to higher ground go to: an upper floor/roof
of a building or climb a tall strong tree.
After a tsunami

Stay tuned to a battery-operated radio for the latest emergency
information.

Help injured or trapped persons and persons requiring special
assistance (infants, elderly).

Do not move seriously injured persons unless they are in
immediate danger of further injury. Call for medical assistance.

Stay out of damaged buildings.

Check for electrical shorts and live wires, gas leaks, damage to
sewage and water lines.

Check food supplies and have tap water tested by the local health
department.

Throw out perishable and contaminated food items.
Be Prepared

Practice evacuation plans with
your friends and family.

Teach your friends and family
about the tsunami hazards and
natural warning signs.

Always keep an emergency supply
stock of items like first aid kit,
canned foods, clean water and
batteries for flashlights or radios.
Knowledge is Safety

As dangerous as tsunamis are they
do not happen very often.

You should not let this hazard
diminish your enjoyment of the
beach and beauty of the ocean.

But if you think a tsunami is
coming, tell others nearby and
move quickly inland and to higher
ground!
Tilly Smith – Lessons Save Life – UNISDR Video Clip 1
Impact of tsunamis

Visit this link online to view a short film of what people
experienced during the 2004 Indian Ocean Tsunami.
http://www.youtube.com/user/UWISeismicResearch#p/f/5
/RDOuwMj7Xzo

When delivering Tsunami Smart presentations it is advised
to show this film to audiences before the Power Point as it
sparks interest in the topic and will generally make the
audience more receptive to your presentation.
Produced by:
Tsunami and Other Coastal Hazards Warning System Project (2010)
www.uwiseismic.com
www.cdema.org
www.weready.org