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High School SMILE Club Activities Winter 2008 Teacher Resources Booklet
SMILE Winter Teachers Workshop Friday February 1st 2008
High School SMILE Club Activities
Winter 2008
Oceanography: Tsunamis
Teacher Resources Booklet
Subduction Zones
Modeling a Tsunami
Tsunami Inundation
Past Evidence for Tsunamis in Oregon
Warning Systems
Communicating Science to the Public
Material Compiled by Laura Dover, Marine Resource Management
Masters GRA, SMILE, Oregon State University
[email protected]
High School SMILE Club Activities Winter 2008 Teacher Resources Booklet
Contents
Title
Page #
Preface: Tsunamis 101
Tsunami Facts…............................................
What Causes a Tsunami…………………………………….
Where do Tsunamis Occur?............................
How Does this Relate to Oregon?....................
Can Tsunamis be Predicted?..........................
What Has Been Done to Prepare for a Tsunami?
Tsunami Safety Advice………………………………………
2
3
5
6
7
8
10
1. Under Pressure: Subduction Zones
Subduction Zones and Tsunamis......................
Icosahedron Globes……………………………………………
11
14
2. Blatant Displacement: Modeling a Tsunami……………………..
16
3. Pop Goes the Wave: Tsunami Inundation………………………..
18
4. Tsunami Shake ‘n’ Quake: Past Evidence
for Tsunamis in Oregon
Evidence of the Great Quake of 1700...............
Native Tales of Cascadia Earthquakes………………
20
22
5. Faster than a Speeding Tsunami: Warning Systems
Tsunami Warning Systems...............................
DART Buoys………………………………………………………….
24
27
6. Talking Risk: Communicating Science to the Public
Public Service Advertising….............................
Well Known PSAs………………………………………………….
30
31
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High School SMILE Club Activities Winter 2008 Teacher Resources Booklet
Tsunamis 101
TSUNAMI FACTS
TSUNAMI:
• From Japanese word, tsu = harbor, nami = wave
• Series of waves produced when ocean (or another body of
water) is rapidly displaced
• Can be caused by earthquakes, volcanic eruptions, landslides,
underwater explosions, meteorite impacts and nuclear
weapons testing
• Has a small wave height offshore, but a very long wavelength
• Tsunamis are often unnoticeable at sea, but can be
devastating onshore – also historically known as tidal waves
as they appear as a huge rushing tide as they hit land
• Can cause widespread damage – force of water can bring
down buildings and move large debris, literally ‘washing’
away coastal areas
• Media/common perception is often different from scientific
fact – viewed as mega waves which tower over the town it
hits, when in fact the wave height is actually relatively small –
it is the continuous incoming of the wave which can make
them deadly
DIFFERENT TYPES?
• Tidal bore (a closer definition of a tidal wave) often confused
with tsunamis, but are very different. Tidal bore is a standing
wave created as tide moves upstream of a river/estuary and
wave of tidal water breaks on top of fresh river water –
density driven. During 2004 Indonesian tsunami, tidal bore
pictures taken in China were sold as photographs of the
tsunami event
• Also Mega-tsunamis exist – these are waves larger than the
tsunami norm – over 40m to giants over 100m – caused by
massive impacts or landslides where the water body cannot
disperse in all directions – often tsunamis are perceived as
these
• Rogue waves also confused with tsunamis – these are
however rare ‘freak’ or extreme ocean waves only
encountered offshore. They are thought to be caused by
diffraction/current focusing of the wave energy, sucking
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•
RECENT
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•
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•
•
•
•
•
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energy from waves around them as part of the wave train,
sometimes encouraged by high winds
Sneaker waves again confused with tsunamis – similar to
rogue waves but encountered onshore and caused by the
focusing of smaller waves into one larger one by constructive
interference – known to catch unwary swimmers and take
them out to sea
TSUNAMIS
Solomon Islands Apr 2007 (8.1 M)
Kuril Islands Nov 2006 (8.1 M)
South of Java Island Jul 2006 (7.7 M)
Indian Ocean Dec 2007 (9.3 m)
Papua New Guinea Jul 1998 (7.1 M)
Hokkaido, Japan Jul 1993 (7.8 M)
Alaska Mar 1964 (9.2 M)
Chile May 1960 (9.5 M)
Hawaii Apr 1946
HISTORICAL TSUNAMIS
• 1929 Newfoundland
• 1908 Messina, Italy
• 1868 Chile
• 1826 Japan
• 1782 South China Sea
• 1755 Lisbon
• 1707 Japan
• 1700 Cascadia
• 1607 Bristol Channel
WHAT CAUSES A TSUNAMI?
UNDERWATER EARTHQUAKES
• Plate boundaries abruptly displaces overlying water –
subduction zone earthquakes most effective
• Displaced water moves under the influence of gravity
radiating across the water body similar to ripples on a pond
• Examples:
o 2004 Indonesian quake
o 1960 Chilean quake
o 1964 Alaskan Good Friday quake
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VOLCANIC ERRUPTIONS
• Water displacement by:
o Volcanic earthquakes
o Undersea eruptions
o Pyroclastic flows
o Caldera collapse
o Landslides/flank failure
o Lahars
o Phreatomagmatic eruptions
o Lava bench collapse
o Airwaves from large explosions
• Examples:
o 1638 Santorini, Greece
o 1883 Krakatoa, Indonesia
o 1980 Mount St Helens
o 1996 Karymsky, Russia
o 2002 Stromboli, Italy
UNDERWATER EXPLOSIONS
• Collision of vessels, e.g. 1917 Halifax explosion
• Nuclear testing, e.g. 1946 BAKER test
LANDSLIDES/ROCKFALLS
• Impact of rock/mud into water causes displacement
• Can be triggered by earthquakes and/or collapse of flank of a
volcanic island
• Can cause mega-tsunamis
• Examples:
o 1958 Lituya Bay, Alaska
o 1963 Vajont dam, Monte Toc, Italy
o 1888 Ritter Island, Papua New Guinea
METEORITE IMPACT
• Huge impact creates mega-tsunamis
• No historical examples known to have produced a tsunami
• Possible evidence from deposits along Gulf Coast of Mexico
and US from 65 million years ago
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High School SMILE Club Activities Winter 2008 Teacher Resources Booklet
WHERE DO TSUNAMIS OCCUR?
As tsunamis are most often generated by earthquakes in marine
coastal regions, they are most commonly found in the Pacific, where
dense oceanic plates, slide underneath lighter continental plates
(subduction zones)
Areas most at risk from tsunamis:
• Western S America
o Chile (May 1960)
o Peru (Jun 2001)
o Ecuador (Jan 1958)
• Western Central America
o Panama (April 1991)
o Costa Rica (Sept 1992)
o Nicaragua (Sept 1992)
o El Salvador (Sept 1992)
o Guatemala (May 1960)
o Mexico
• Western USA
o California (Mar 1964)
o Oregon (Mar 1964)
o Washington (Mar 1964)
o Alaska (Mar 1964)
o Hawaii (Apr 1946)
• Western Canada
o British Columbia (Mar 1964)
• Africa
o Somalia (Dec 2004)
o Madagascar
o Seychelles (Dec 2004)
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High School SMILE Club Activities Winter 2008 Teacher Resources Booklet
•
•
Asia
o Japan (July 1993)
o Sri Lanka (Dec 2004)
o India (Dec 2004)
o Thailand (Dec 2004)
o Indonesia (Dec 2004)
o Malaysia (Dec 2004)
o Philippines (Aug 1976)
o Myanmar (Burma) (Dec 2004)
Australasia
o Papua New Guinea (Jul 1998)
o New Zealand (Mar 1947)
o Solomon Islands (Apr 2007)
o Samoa (May 2006)
o Fiji (May 2006)
o Tonga (May 2006)
Although Europe has shown less tsunami activity in recent years,
history has shown accounts of tsunami destruction in areas such as
Portugal, Greece, UK and France.
HOW DOES THIS RELATE TO OREGON?
The Oregon coast is part of the Northwest tsunami risk area,
• Alongside California, Washington and BC (Canada)
• Tsunami waves propagating across the pacific could
potentially threaten Oregon from East or South Pacific sources
• However we are more at risk from underwater earthquakes
sourced at Alaska or Hawaii
The most devastating tsunami would occur as a result of a subduction
earthquake off the Oregon coast
o The Cascadia Subduction Zone – very long sloping fault
stretching from Vancouver island to Northern California
o Juan de Fuca plate slides under North American plate
o Last subduction earthquake thought to have been 1700
– based on Native American legends and sediment data
o Thought to occur average of every 500yrs, thus next
one is supposedly due by 2200..uh oh!
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High School SMILE Club Activities Winter 2008 Teacher Resources Booklet
CAN TSUNAMIS BE PREDICTED?
No! In the same context as earthquakes cannot be predicted
2 most likely tsunami sources
• LOCAL SOURCE - i.e. cascadia subduction zone earthquake
• DISTANT SOURCE – i.e. from Alaska
But, much research is being carried out into the frequency and
patterns of tsunami occurrence, whilst maintaining a more accurate
warning system
• If Cascadia subduction zone earthquake occurs then warning
would be the earthquake movement itself – as soon as you
feel it move to higher ground! Warning system is your feet! In
this situation, the actual warning system may be damage due
to the size of the quake, this why it is important to increase
tsunami awareness on the west coast
• Tsunamis propagating from Eastern Pacific or Alaska/Hawaii
would give a varying number of hours of warning.
Oregon warning system from West Coast and Alaska Tsunami warning
centre
• DART buoy system (Deep-ocean Assessment and Reporting of
Tsunamis)
Palmer, Alaska monitors for earthquakes and subsequent
tsunami events. If a tsunami is generated, they issue
tsunami watches and warnings, as well as tsunami
information bulletins for Alaska, British Columbia and
Washington, Oregon and California.
• Tsunameter measures seismic information from earthquake
event, sends signal to surface buoy
• Surface buoy measures sea level changes and reports back to
warning centers
• DART system can also send data on request (for example
tsunami propagation from earthquakes outside that locations
seismic monitoring area)
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High School SMILE Club Activities Winter 2008 Teacher Resources Booklet
WHAT HAS BEEN DONE TO PREPARE FOR A
TSUNAMI?
Upon receipt of tsunami watches and warnings:
• Coastal National Weather Service (NWS) offices such as those
in Seattle and Portland, activate the Emergency Alert System
(EAS) via NOAA Weather Radio
• All broadcasters (TV, AM/FM radio, cable TV) receive the
tsunami EAS message simultaneously as well as those with
weather radio receivers in homes, businesses, schools, health
care facilities, etc. NOAA Weather Radio also activates the AllHazard Alert Broadcast (AHAB) units located in remote coastal
areas, alerting people in those isolated locations.
• Local emergency management officials can decide to activate
the Emergency Alert System (EAS) to evacuate low-lying
coastal areas in advance of the initial tsunami wave
• EAS messages are also received by broadcasters, weather
radio receivers and All Hazard Alert Broadcasts (AHABs) to
help provide widespread dissemination of these messages
Types of Warnings
LOCAL SOURCE
• If you feel violent shaking for several minutes, head for
higher ground. The earthquake is your warning. The most
likely source for a violent earthquake of this magnitude is
from the Cascadia Subduction Zone just off our coast. The
last associated earthquake was estimated to be 9.0 in
magnitude on Jan 26, 1700, and was similar to the Dec 26,
2004 Sumatra 9.0 magnitude earthquake and subsequent
Indian Ocean Basin tsunami.
**THE EARTHQUAKE IS THE ALERT TO AN INCOMING TSUNAMI
AS WARNING SYSTEMS MAY FAIL IN SUCH A MAJOR
EARTHQUAKE**
DISTANT SOURCE
• Pacific-wide Tsunami Warning. A Pacific-wide tsunami
warning bulletin is issued by the PTWC after confirmation has
been received that a tsunami has been generated in the
Pacific that has caused damage, or has the potential to cause
damage, at distances greater than 1000 kilometers from the
epicenter, and thus poses a widespread threat to any
populated coastal area within the Pacific Basin
• Regional Tsunami Warning. A regional tsunami warning
bulletin is a tsunami warning issued initially to coastal areas
near the earthquake epicenter. It is usually based only on
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•
•
•
•
•
•
seismic information without tsunami confirmation, and is
initially issued as a means of providing the earliest possible
alert of a potentially destructive tsunami to the population
near the epicentral area of a potentially tsunamigenic
earthquake
Urgent Local Tsunami Warning. An urgent local tsunami
warning is a tsunami warning issued by the PTWC to Hawaii
for tsunamis generated in Hawaiian coastal waters. It may be
based only on seismic information without tsunami
confirmation, or on a combination of seismic and sea level
data, and is issued as a means of providing the earliest
possible alert of a potentially destructive local tsunami. Areas
in an urgent local tsunami warning may have only minutes or
seconds before tsunami waves arrive, so urgent action is
required to save lives
Final Warning Supplement. A final warning supplement
bulletin is issued following a damaging or potentially
damaging tsunami
Warning Cancellation. A warning cancellation is issued as
the final bulletin indicating when there is no longer the threat
of a damaging tsunami
Regional Tsunami Watch. A regional tsunami watch is a
tsunami watch issued in conjunction with a regional tsunami
warning to coastal areas near the earthquake epicenter, but
outside the warning area. Areas in a regional tsunami watch
are generally less than six hours from the estimated tsunami
arrival time, and a list of estimated arrival times for watch
areas is provided in the bulletin.
Tsunami Advisory Bulletin. A tsunami advisory bulletin is
issued to areas not currently in either warning or watch status
when a tsunami warning has been issued for another region
of the Pacific.
Tsunami Information Bulletin. A tsunami information
bulletin is issued for informational purposes for events that
will not cause a destructive tsunami but were large enough in
size to have been detected by the tsunami warning center’s
seismic monitoring networks. Some of these earthquakes may
have been large enough, however, to cause earthquakerelated damage.
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High School SMILE Club Activities Winter 2008 Teacher Resources Booklet
Under Pressure: Subduction Zones
Subduction Zones and Tsunamis
A subduction zone is an area on Earth where two tectonic plates
meet and move towards one another, with one sliding underneath the
other and moving down into the mantle, at rates typically measured in
centimeters per year. An oceanic plate ordinarily slides underneath a
continental plate; this often creates an orogenic zone with many
volcanoes and earthquakes. In a sense, subduction zones are the
opposite of divergent boundaries, areas where material rises up from
the mantle and plates are moving apart.
Subduction zones mark sites of convective downwelling of the Earth's
lithosphere (the crust plus the strong portion of the upper mantle).
Subduction zones exist at convergent plate boundaries where one
plate of oceanic lithosphere converges with another plate and sinks
below it to depth of approximately 100 km. At that depth the
peridotite of the oceanic slab is converted to eclogite, the density of
the edge of the oceanic lithosphere increases and it sinks into the
mantle. It is at subduction zones that the Earth's lithosphere, oceanic
crust, sedimentary layers, and trapped water are recycled into the
deep mantle. Earth is the only planet where subduction is known to
occur; neither Venus nor Mars have subduction zones. Without
subduction, plate tectonics could not exist and Earth would be a very
different planet: Earth's crust would not have differentiated into
continents and oceans and all of the solid Earth would lie beneath a
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High School SMILE Club Activities Winter 2008 Teacher Resources Booklet
global ocean.
Subduction results from the difference in density between lithosphere
and underlying asthenosphere. Where, very rarely, lithosphere is
denser than asthenospheric mantle, it can easily sink back into the
mantle at a subduction zone; however, subduction is resisted where
lithosphere is less dense than underlying asthenosphere. Whether or
not lithosphere is denser than underlying asthenosphere depends on
the nature of the associated crust. Crust is always less dense than
asthenosphere or lithospheric mantle, but because continental crust is
always thicker and less dense than oceanic crust, continental
lithosphere is always less dense than oceanic lithosphere. Oceanic
lithosphere is generally not denser than asthenosphere but continental
lithosphere is lighter. Exceptionally, the presence of the large areas of
flood basalt that are called large igneous provinces (LIPs), which result
in extreme thickening of the oceanic crust, can cause some sections of
older oceanic lithosphere to be too buoyant to subduct. Where
lithosphere on the downgoing plate is too buoyant to subduct, a
collision occurs, hence the adage "Subduction leads to orogeny". Most
subduction zones are arcuate, where the concave side is directed
towards the continent. This is especially so where a back-arc basin
develops between the subduction zone and the continent.
An example of a subduction zone is that of the Cascadia Subduction
Zone, which is located off the Pacific Northwest Coast. The zone
separates the Juan de Fuca, Explorer, Gorda and the North American
Tectonic Plates.
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High School SMILE Club Activities Winter 2008 Teacher Resources Booklet
The width of the Cascadia subduction zone fault varies along its
length, depending on the temperature of the subducted oceanic plate,
which heats up as it is pushed deeper beneath the continent. As it
becomes hotter and more molten, it eventually loses the ability to
store mechanical stress and generates earthquakes.
The Cascadia subduction zone can produce
very large earthquakes, magnitude 9.0 or
greater, if rupture occurred over its whole
area. When the "locked" zone stores up
energy for an earthquake, the
"transition" zone, although somewhat
plastic, can rupture. Thermal and
deformation studies indicate that the
locked zone is fully locked for 60
kilometers (about 40 miles) down dip
from the deformation front. Further
down dip, there is a transition from
fully locked to aseismic sliding.
(Nedimovic, et al., 2003)
In 1999, a group of Continuous Global
Positioning System sites registered a
brief reversal of motion of
approximately 2 centimeters (0.8
inches) over a 50 kilometer by 300kilometer (about 30 mile by 200 mile)
area. The movement was the equivalent of a 6.7 magnitude
earthquake. (Dragert, et al., 2001) The motion did not trigger an
earthquake and was only detectable as silent, non-earthquake seismic
signatures. (Rogers & Dragert, 2003)
The last known great earthquake in the northwest was in January of
1700, the Cascadia Earthquake. Geological evidence indicates that
great earthquakes may have occurred at least seven times in the last
3,500 years, suggesting a return time of 300 to 600 years. There is
also evidence of accompanying tsunamis with every earthquake, and
one line of evidence for these earthquakes are tsunami damage, and
through Japanese records of tsunamis.
A future rupture of the Cascadia Subduction Zone would cause
widespread destruction throughout the Pacific Northwest.
Other similar subduction zones in the world usually have such
earthquakes every 100–200 years; the longer interval here may
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High School SMILE Club Activities Winter 2008 Teacher Resources Booklet
indicate unusually large stress buildup and subsequent unusually large
earthquake slip.
Subduction zones are capable of producing tsunamis. Here, a sudden
pressure release (built up by frictional forces between the plates) and
subsequent movement of the zone (the earthquake) causes a massive
displacement of water from its equilibrium position, creating a
tsunami. Gravity works to restore the water to its equilibrium position
as the waves travel outward from the origin in all directions. The water
transfers the energy of the subduction zone earthquake.
Icosahedron Globes
The Ancient Greeks discovered that a representation of a spherical
object could be made from a flat sheet of paper using specific flat
polygons, for example an octahedron is a solid object comprised of 8
triangles or ‘faces’. An increase in the number of faces on a regularsized solid will increase the more spherical look of the object. With 20
faces, the icosahedron is the best "flat" sphere available and hence will
be used to make a globe.
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High School SMILE Club Activities Winter 2008 Teacher Resources Booklet
Icosahedron
Each face of the icosahedron displays a part of the (nearly-spherical)
Earth's surface as a flat map and once folded, adjacent triangles are
joined exactly at their closest edges and the cut-out pattern forms the
complete globe with the North and South Poles at opposite vertices.
Facts about icosahedrons!
•
Many viruses, e.g. herpes virus, have the shape of an icosahedron.
Viral structures are built of repeated identical protein subunits and
the icosahedron is the easiest shape to assemble using these
subunits. A regular polyhedron is used because it can be built from
a single basic unit protein used over and over again; this saves
space in the viral genome.
•
In some role-playing games, the twenty-sided die is used in
determining success or failure of an action. This die is in the form of
a regular icosahedron. It may be numbered from "0" to "9" twice.
•
An icosahedron is the three-dimensional game board for
Icosagame, formerly known as the Ico Crystal Game.
•
An icosahedron is used in the board game Scattergories to choose a
letter of the alphabet.
•
The die inside of a Magic 8-Ball that has printed on it 20 answers to
yes-no questions is a regular icosahedron.
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High School SMILE Club Activities Winter 2008 Teacher Resources Booklet
Blatant Displacement: Modeling a Tsunami
A tsunami is a series of waves created when a body of water, such as
an ocean, is rapidly displaced. Tsunamis have a much smaller
amplitude (wave height) offshore, and a very long wavelength (often
hundreds of miles long), which is why they generally pass unnoticed at
sea, forming only a passing "hump" in the ocean. Tsunamis have been
historically labeled tidal waves because as they approach land, they
take on the characteristics of a violent onrushing tide rather than the
sort of cresting waves that are formed by wind action upon the ocean
(with which people are more familiar). Since they are not actually
related to tides the term is considered misleading and its usage is
discouraged by oceanographers.
A tsunami can be generated when the plate boundaries abruptly
deform and vertically displace the overlying water. Such large vertical
movements of the Earth's crust can occur at plate boundaries.
Subduction earthquakes are particularly effective in generating
tsunami. Also, one tsunami in the 1940's in Hilo, Hawaii, was actually
caused by an earthquake on one of the Aleutian Islands in Alaska. That
earthquake was 7.8 on the Richter scale.
In fluid mechanics, displacement occurs when an object is immersed in
a fluid, pushing it out of the way and taking its place, so that it can be
weighed. In the case of a tsunami being created by a subduction zone
earthquake, it is the plate boundaries that create a sudden
deformation that creates the displacement.
The objective of tsunami modeling research is to develop numerical
models for faster and more reliable forecasts of tsunamis propagating
through the ocean and striking coastal communities. The primary
responsibility of the NOAA Center for Tsunami Research (NCTR) is to
provide assistance to the Tsunami Warning Centers (TWC) in the form
of Forecast Modeling software products specifically designed to support
the Tsunami Warning Center’s forecasting operations. In addition to
this, the NCTR has traditionally been committed to Inundation
Modeling to assist coastal communities in their efforts to assess the
risk, and mitigate the potential of tsunami hazard
Forecast modeling provides an estimate of wave arrival time, wave
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High School SMILE Club Activities Winter 2008 Teacher Resources Booklet
height and inundation area immediately after a tsunami event.
Tsunami forecast models are run in real time while a tsunami is
propagating in the open ocean, consequently they are designed to
perform under very stringent time limitations.
Computerized
tsunami model
displacing water at
its source and
moving omni directionally across
the Pacific Ocean
Given the time constraints of this type of study, the process of
computing the three stages of tsunami modeling, namely, wave
generation, propagation and inundation has been expedited by
generating a database of pre-computed scenarios. The pre-computed
database contains information about tsunami propagation in the open
ocean from a multitude of potential sources. When a tsunami event
occurs, an initial source is selected from the pre-computed database.
In the initial stages of the tsunami, this selection is based only on the
available seismic information for the earthquake event. As the wave
propagates across the ocean and successively reaches the DART
systems these report the recorded sea level information back to the
TWCs which, in turn, process the information and produce a new and
more refined estimate of the tsunami source. The result is an
increasingly accurate forecast of the tsunami that can be used to
issue, watches, warnings or evacuations.
When an event similar to one of the pre-computed scenarios occurs,
the available propagation information is used to compute the last
stage of the study, wave inundation.
[http://nctr.pmel.noaa.gov/model.html]
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High School SMILE Club Activities Winter 2008 Teacher Resources Booklet
Pop Goes the Wave: Tsunami Inundation
Tsunamis rank high on the scale of natural disasters. Since 1850
alone, tsunamis have been responsible for the loss of over 420,000
lives and billions of dollars of damage to coastal structures and
habitats. Most of these casualties were caused by local tsunamis that
occur about once per year somewhere in the world. For example, the
December 26, 2004, tsunami killed about 130,000 people close to the
earthquake and about 58,000 people on distant shores. Predicting
when and where the next tsunami will strike is currently impossible.
Once the tsunami is generated, forecasting tsunami arrival and impact
is possible through modeling and measurement technologies
[http://www.tsunami.noaa.gov/tsunami_story.html]
An inundation modeling study attempts to recreate the tsunami
generation in deep or coastal waters, wave propagation to the impact
zone and inundation along the study area. To reproduce the correct
wave dynamics during the inundation computations high-resolution
bathymetric and topographic grids are used in this type of study. The
high quality bathymetric and topographic data sets needed for
development of inundation maps require maintenance and upgrades as
better data becomes available and coastal changes occur.
Inundation studies can be conducted taking a probabilistic approach in
which multiple tsunami scenarios are considered, and an assessment
of the vulnerability of the coast to tsunami hazard is evaluated, or they
may focus on the effect of a particular ‘worst case scenario” and
assess the impact of such a particularly high impact event on the areas
under investigation.
The results of a tsunami
inundation study should
include information about the
maximum wave height and
maximum current speed as a
function of location, maximum
inundation line, as well as time
series of wave height at
different locations indicating
wave arrival time. This
information can be used by
emergency managers and
urban planners primarily to
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establish evacuation route and location of vital infrastructure.
[http://nctr.pmel.noaa.gov/model.html]
Rapid growth in the last twenty years has led to the development of
the coastal areas in most of the developing or developed Pacific
nations. This is the result of a population explosion and of
technological and economic developments that have made the use of
the coastal zone more necessary than before. Fortunately, tsunami are
not frequent events and therefore their effects have not been felt
recently in all developing areas of the Pacific. History, however, has
proved that although infrequent, destructive tsunamis indeed do occur.
A major Pacific-wide tsunami is likely to occur in the near future.
Among the countries bordering on the Pacific, a number are not
prepared for such an event while others have let their guard down.
The social and economic impact of future tsunami, therefore, cannot
be overlooked.
Part of a tsunami
inundation map
for Kodiak
produced by
Alaska scientists.
Image courtesy
Elena Suleimani
[http://www.gi.al
aska.edu/Science
Forum/ASF17/17
34.html].
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High School SMILE Club Activities Winter 2008 Teacher Resources Booklet
Tsunami Shake ‘n’ Quake: Past Evidence for Tsunamis in
Oregon
The January, 1700 Cascadia Subduction Zone earthquake and tsunami
Between 9:00 PM and 10:00 PM, local time, on January 26th 1700, a
great earthquake shook the Pacific Northwest. This quake, with
magnitude estimated at 9.0, rocked the region with strong shaking for
several long minutes while coastal Washington plummeted as much as
1.5 meters relative to coastal waters.
How is it possible to know that any event on the Cascadia Subduction
ever occurred, let alone to place it within one hour of its occurrence
300 years ago? Let the evidence speak for itself and discover an
ancient earthquake in the Pacific Northwest.
Evidence of the Great Quake of 1700
•
Land Levels - Geological evidence shows that Washington's coast
cycles through changes in land levels that subduction zone quakes
typically produce.
•
Tree Rings - Ancient trees along Washington's coast put an accurate
date on a likely seismic event occurring in the Pacific Northwest.
•
Tsunami Traces - Uncharacteristic sand deposits in Washington's
coastal soil give evidence of local tsunamis.
•
Historic Records - Japanese government records from 1700
describe a large tsunami likely originating from the Pacific
Northwest.
•
Turbidite Record - Layers of sediment off Washington's coast show
that widespread, simultaneous shaking of the region was very
likely.
•
Native Tales - Native American stories from the Pacific Northwest
describe an event strikingly similar to a large Cascadia subduction
zone quake.
Turbidite evidence for Cascadia Subduction Zone Earthquakes
Rivers carry sediment (soil and other debris) into the ocean, and
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sediment collects on the continental shelf and continental slope, which
slopes into deeper water. More and more material builds up on the
continental shelf sea floor until it becomes unstable and slides down
the continental slope, much like an avalanche, in what is called a
turbidity current.
The resulting layer of sediment this current deposits on the sea floor is
called a turbidite.
A number of events can potentially trigger turbidity currents. These
events include tsunamis, storm induced waves, slope failures, and
earthquakes. The turbidite record strongly suggests the latter —
coastal Washington and Oregon experienced strong coast-wide shaking
typical of a large subduction zone earthquake.
Large storms are an unlikely source of a coast- wide event because
these storms produce waves not much larger than smaller, more
common storms. If common and rare storms produce waves that are
approximately the same magnitude, the turbidite record should reflect
more than 13 events in the last 5,000 years.
The 1964 Alaska earthquake generated the most recent damaging
tsunami that struck the Oregon-Washington coast. Although this
earthquake is one of the largest seismic events of the 20th century, it
did not produce any recorded turbidites. If this large tsunami did not
trigger a turbidity current, it is highly unlikely the turbidite record
reflects the occurrence of tsunamis.
In a slope failure, so much sediment develops on the inclined
continental slope that it slips, much like an avalanche triggered by
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excessive snowfall. When enough sediment accumulates at a given
point on a coastal slope, slope failure will occur. This underwater
avalanche can cause turbidity currents to spread sediment throughout
the underwater sea channels. Although these kinds of currents are
likely to occur given enough time, the different rates of sedimentation
and inclination of coastal regions make the synchronized turbidity
currents implied shown in the core samples unlikely.
Cascadia zone earthquakes, on the other hand, prove to provide
enough force and affect a large enough region of coast to have caused
the turbidites in the core samples. Subduction zone earthquakes are
cyclical and have large recurrence intervals, as do turbidity currents.
Radiocarbon dating of each turbidite in Adams' core samples show a
recurrence interval of about 590 years, closely matching the interval of
coastal subsidence observed in coastal Washington.
The Cascadia Subduction Zone - Latest Research
The latest exciting scientific news about the Cascadia Subduction Zone
(first discovered in 2001, and confirmed in 2002) is the observation of
silent, aseismic (no shaking) slip events on the CSZ. The silent slip
events have occurred regularly, every 14 months, since at least 1998.
The largest of these events involved a 60-kilometer-by-300-km area
about 30 km or more beneath Vancouver Island and Puget Sound that
slipped about 30 mm over a period of 12 days or so.
[http://www.ess.washington.edu/SEIS/PNSN/HAZARDS/CASCADIA/turbidite_record.html]
Native Tales and Traditions of Cascadia Megathrust Earthquakes
Many Native American (U.S.) and First Nations (Canada) stories
describe earthquake effects: shaking, tsunamis, and subsidence.
Native peoples have inhabited the Cascadia coast for thousands of
years and witnessed cycle after cycle of great earthquakes. Some
stories are myths, others are historical.
One northern-California story describes a huge earthquake in which
elders tell the young to run for high ground because of ensuing
floodwaters. After spending a cold night in the hills, the young people
find that all trace of their village has been washed away.
Other stories depict supernatural beings that caused the earthquake
while at battle. Stories from the Hoh and Quileute tribes of the
Olympic Peninsula of northwest Washington describe an epic battle
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between the supernatural beings Thunderbird and Whale.
"The great Thunderbird finally carried the weighty animal to its nest in
the lofty mountains and there was the final and terrible contest fought.
There was a shaking, jumping up and trembling of the earth beneath,
and a rolling up of the great waters."
By examining a variety of Native American tribal accounts, Ruth
Ludwin, Deborah Carver and other researchers have identified
consistencies in Native American lore that support a great earthquake
in the Pacific Northwest.
[http://www.ess.washington.edu/SEIS/PNSN/HAZARDS/CASCADIA/native_lore.html]
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High School SMILE Club Activities Winter 2008 Teacher Resources Booklet
Faster than a Speeding Tsunami: Warning Systems
A tsunami warning system is a system to detect tsunamis and issue
warnings to prevent loss of life and property. It consists of two equally
important components: a network of sensors to detect tsunamis and a
communications infrastructure to issue timely alarms to permit
evacuation of coastal areas.
There are two distinct types: international tsunami warning systems,
and regional warning systems. Both depend on the fact that, while
tsunamis travel at between 500 and 1,000 km/h (around 0.14 and
0.28 km/s) in open water, earthquakes can be detected almost at once
as seismic waves travel with a typical speed of 4 km/s (around 14,400
km/h). This gives time for a possible tsunami forecast to be made and
warnings to be issued to threatened areas, if warranted.
Unfortunately, until a reliable model is able to predict which
earthquakes will produce significant tsunamis, this approach will
produce many more false alarms than verified warnings. In the correct
operational paradigm, the seismic alerts are used to send out the
watches and warnings. Then, data from observed sea level height
(either shore based via tide gauges or deep ocean DART buoys) are
used to verify the existence of a tsunami. Other systems have been
proposed to augment the warning paradigm. For example, it has been
suggested that the duration and frequency content of t-wave energy
(which is earthquake energy trapped in the ocean SOFAR channel) is
indicative of an earthquakes tsunami potential [Salzberg, 2006]. The
first rudimentary system to alert communities of an impending
tsunami was attempted in Hawaii in the 1920s. More advanced
systems were developed in the wake of the April 1, 1946 and May 23,
1960 tsunamis which caused massive devastation in Hilo, Hawaii.
[http://en.wikipedia.org/wiki/Tsunami_warning_system]
How does the Tsunami Warning System work?
There are two sources of tsunami for Washington coastal waters - a
distant source and a local source.
Local source - if you feel violent shaking for several minutes, head
for higher ground. The earthquake is your warning. The most likely
source for a violent earthquake of this magnitude is from the Cascadia
Subduction Zone just off our coast. The last associated earthquake
was estimated to be 9.0 in magnitude on Jan 26, 1700, and was
similar to the Dec 26, 2004 Sumatra 9.0 magnitude earthquake and
subsequent Indian Ocean Basin tsunami.
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Simulations show the initial tsunami wave from the 1700 event
reached the coast in 20 to 30 minutes - so time is limited. Geologic
history showed waves with this event were as high as 30 feet. So you
must get at least that high above sea level.
To top it off, the earthquake will also result in the coastal area
subsiding as much as six feet, meaning the ground and roadways will
likely be very uneven, and you are now that much lower to sea level.
Since the roads will be in pieces, evacuation must be on foot. Another
form of evacuation is vertical evacuation into a sturdy building of at
least three stories and climb to at least the third story.
Other area earthquake faults could produce such strong violent
quakes, such as the Seattle fault that produced a tsunami in Puget
Sound about 1100 years ago. Yet, the most likely source for a local
tsunami is the Cascadia Subduction Zone off our coast
A Distant Source - The perimeter of the Pacific Ocean Basin,
nicknamed the Ring of Fire, has a number of earthquake sources that
can produce strong earthquakes of 7.0 magnitude or greater. During
the 20th century, there were three 9.0 magnitude or greater quakes,
the last was the 1964 Alaskan quake of 9.2 magnitude that produced a
tsunami throughout the Pacific Basin. These kinds of earthquakes
permit a lead-time of hours before their subsequent tsunami reaches
the Washington coastline. Tsunamis from distant locations like Japan
or Chile will take over 10 hours to get here, while from Alaska, only
three to six hours.
Tsunamis generated from both sources of earthquakes do penetrate
into the Puget Sound region via the Strait of Juan de Fuca and up
coastal rivers, harbors and bays, but lose energy as they move further
inland.
Tsunami Warning System has been put into place to help minimize
loss of life and property. The West Coast/Alaska Tsunami Warning
Center in Palmer, Alaska monitors for earthquakes and subsequent
tsunami events. If a tsunami is generated, they issue tsunami
watches and warnings, as well as tsunami information bulletins for
Alaska, British Columbia and Washington, Oregon and California.
The Pacific Tsunami Warning Center in Ewa Beach, Hawaii provides
the same service for the Aloha state as well as all other American
territories in the Pacific. They also serve as the International Tsunami
Warning Center for 25 other member countries in the Pacific Ocean
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Basin.
Both of the tsunami warning centers use earthquake information, tide
gauges and now a new tool from NOAA - tsunami detection buoys,
developed by NOAA's Pacific Marine Environmental Laboratory. Six of
these buoys are now deployed in the north Pacific to help scientists
determined whether a tsunami has been generated and moving across
the Pacific before reaching North American coastlines - another tool in
the tsunami warning centers warning toolbox to help avoid any false
alarms. More of these buoys would help detection as well as provide
backup to each other since the buoys suffer outages in the harsh North
Pacific Ocean.
Once a tsunami watch or warning is issued
Upon receipt of tsunami watches and warnings, coastal National
Weather Service (NWS) offices such as those in Seattle and Portland,
activate the Emergency Alert System (EAS) via NOAA Weather Radio.
All broadcasters (TV, AM/FM radio, cable TV) receive the tsunami EAS
message simultaneously as well as those with weather radio receivers
in homes, businesses, schools, health care facilities, etc. NOAA
Weather Radio also activates the All-Hazard Alert Broadcast (AHAB)
units located in remote coastal areas, alerting people in those isolated
locations.
Upon receipt of tsunami watch and warning messages, local
emergency management officials (see Clallam County, WA as an
example) can decide to activate the Emergency Alert System (EAS) to
evacuate low-lying coastal areas in advance of the initial tsunami
wave. Their EAS messages are also received by broadcasters, weather
radio receivers and All Hazard Alert Broadcasts (AHABs) to help
provide widespread dissemination of these messages. Follow the
directions provided by your area emergency management officials they will help save your life and those of your loved ones.
If you want your own tsunami warning message receipt system, obtain
a NOAA weather radio receiver with EAS-programmable features. They
are available from most radio electronic retailers and on the Internet.
Role of Education in developing the Tsunami Resilient Community
Education is another key element in the tsunami warning system.
Many coastal areas have designated tsunami inundation zones and
marked evacuation routes to assist residents and visitors to higher
ground. Emergency management officials also distribute tsunami
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High School SMILE Club Activities Winter 2008 Teacher Resources Booklet
education information, conduct community meetings and workshops,
and many more awareness activities.
The National Weather Service recognizes communities with strong
tsunami warning and awareness programs through the TsunamiReady
Community program. Such communities are recognized for their
efforts to enhance their tsunami warning system, widespread use of
weather radio receivers and community awareness activities.
TsunamiReady road signs are also a part of NWS recognition.
[http://www.tsunami.noaa.gov/warnings_forecasts.html]
About DART™ tsunami monitoring buoys
How the DART™
Network helps
forecasting:
To ensure early
detection of tsunamis
and to acquire data
critical to real-time
forecasts, NOAA has
placed Deep-ocean
Assessment and
Reporting of Tsunami
(DART™) stations at
sites in regions with a
history of generating
destructive tsunamis. NOAA completed the original 6-buoy operational
array (map of original six stations) in 2001 and plans to expand to a
full network of 39 stations by the end of 2008 (Planned DART™ Array).
Originally developed by NOAA, as part of the U.S. National Tsunami
Hazard Mitigation Program (NTHMP), the DART™ Project was an effort
to maintain and improve the capability for the early detection and realtime reporting of tsunamis in the open ocean.
DART™ presently constitutes a critical element of the NOAA Tsunami
Program. The Tsunami Program is part of a cooperative effort to save
lives and protect property through hazard assessment, warning
guidance, mitigation, research capabilities, and international
coordination. NOAA’s National Weather Service (NWS) is responsible
for the overall execution of the Tsunami Program. This includes
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High School SMILE Club Activities Winter 2008 Teacher Resources Booklet
operation of the U.S. Tsunami Warning Centers (TWC) as well as
leadership of the National Tsunami Hazard Mitigation Program. It also
includes the acquisition, operations and maintenance of observation
systems required in support of tsunami warning such as DART™, local
seismic networks, coastal, and coastal flooding detectors. NWS also
supports observations and data management through the National
Data Buoy Center (NDBC).
[http://www.ndbc.noaa.gov/dart/dart.shtml]
The information collected by a network of DART™ systems positioned
at strategic locations throughout the ocean plays a critical role in
tsunami forecasting. The map at right shows the conceptual plan for
DART™ locations.
When a tsunami event occurs, the first information available about the
source of the tsunami is based only on the available seismic
information for the earthquake event. As the tsunami wave propagates
across the ocean and successively reaches the DART™ systems, these
systems report sea level information measurements back to the
Tsunami Warning Centers, where the information is processed to
produce a new and more refined estimate of the tsunami source. The
result is an increasingly accurate forecast of the tsunami that can be
used to issue watches, warnings or evacuations.
DART™ buoy development
Over the past 20 years, NOAA's Pacific Marine Environmental
Laboratory (PMEL) has identified the requirements of the tsunami
measurement system through evolution in both technology and
knowledge of deep ocean tsunami dynamics. The tsunami forecasting
technology developed at PMEL is based on the integration of real-time
measurements and modeling technologies, a well-tested approach
used in most hazard forecast systems.
The first-generation DART™ design featured an automatic detection
and reporting algorithm triggered by a threshold wave-height value.
The DART™ II design incorporated two-way communications that
enables tsunami data transmission on demand, independently of the
automatic algorithm; this capability ensures the measurement and
reporting of tsunamis with amplitude below the auto-reporting
threshold. The next generation DART™ ETD (Easy To Deploy) buoy is
presently under development at PMEL.
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High School SMILE Club Activities Winter 2008 Teacher Resources Booklet
Developed by PMEL and deployed operationally by NOAA's National
Data Buoy Center (NDBC), DART™ is essential to fulfilling NOAA's
national responsibility for tsunami hazard mitigation and warnings.
[http://nctr.pmel.noaa.gov/Dart/[
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High School SMILE Club Activities Winter 2008 Teacher Resources Booklet
Talking Risk: Communicating Science to the Public
Public service advertising is the use of commercial advertising
techniques for non-commercial purposes. Typical topics for public
service advertising include public health/public safety issues,
emergency preparedness instructions, natural resources conservation
information, and other topics of broad interest.
Public service advertising campaigns are widespread around the world.
Such advertising is generally produced and distributed on a
cooperative basis by governmental agencies or nonprofit organizations
acting in concert with private advertising and mass media companies.
In most cases, the nonprofit provides the programming that is to be
advertised, while the participating advertising agency and media
companies provide creative services, media planning, and
dissemination services.
A public service announcement (PSA) or community service
announcement (CSA) is a non-commercial advertisement typically on
radio or television, ostensibly broadcast for the public good.
The main concept is to modify public attitudes by raising awareness
about specific issues.
The most common topics of PSAs are health and safety, although any
message considered to be "helpful" to the public can be a PSA. A
typical PSA will be part of a public awareness campaign to inform or
educate the public about an issue such as smoking or compulsive
gambling.
Often, an organization releasing a PSA may enlist the support of a
celebrity, examples being Michael J. Fox's PSAs in the U.S. supporting
research into Parkinson's Disease, or Crips street gang leader Stanley
"Tookie" Williams speaking from prison, urging youth not to join
gangs.
Some religious groups produce PSAs on non-religious themes such as
family values, as a means of increasing awareness of their church, and
to show the role the church has in serving the community. Examples
include the long-running "Homefront" campaign from The Church of
Jesus Christ of Latter-day Saints, and more recently the United
Methodist Church. Also, the military produces PSAs to recruit enlistees,
alongside paid advertising and sponsorship efforts.
In the U.S, the role of PSAs was affected by deregulation of the
broadcasting industry in the 1980s. Previously, a broadcast license
was assigned to a television or radio station that was expected to
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High School SMILE Club Activities Winter 2008 Teacher Resources Booklet
serve as a "public trustee" by airing, among other requirements,
frequent PSAs. Continued licensure no longer depends strictly on
programming content, and the number of PSAs that are deliberately
scheduled has declined, yet new PSAs continue to be produced and
aired.
Today, TV and radio stations will use PSAs to demonstrate their
commitment to a particular cause, or as an easy way to fill unsold
commercial time. Some large non-profit organizations, such as the
American Cancer Society and Red Cross, choose to ensure play by
purchasing commercial time for their campaigns. Smaller
organizations, such as the American Indian College Fund, rely solely
on voluntary media space to get their message out.
The Ad Council is the largest producer of PSAs in the United States,
many of which involve a substantial budget and are distributed
commercially. Other producers such as Salo Productions specialize in
traditional PSAs distributed to station PSA directors.
Well-known PSAs
Don't Copy That Floppy
The Incredible Crash Dummies: "You can learn a lot from a Dummy."
G.I. Joe and Transformers: "And knowing is half the battle!"
Mr. Funercise
Just Say No
Crying Indian (sponsored by Keep America Beautiful)
McGruff the Crime Dog: "Take a bite out of crime!"
Smokey Bear: "Only you can prevent forest fires!" and "Only You
Can Prevent wildfires!"
• Woodsy Owl: "Give a hoot, don't pollute!" and "Lend a hand — care
for the land!"
• Click It or Ticket
• FUR...You Deserve It (anti-fur trading)
•
•
•
•
•
•
•
•
[http://en.wikipedia.org/wiki/Public_service_advertising]
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