Download Tsunami Science and Hazard - Manual

Strengthening Tsunami Warning
and Emergency Responses:
1-Day Tsunami Awareness Seminar
Tsunami Science and Hazard
Slide Presentations
United Nations
Educational, Scientific and
Cultural Organization
Intergovernmental
Oceanographic
Commission
The International
Tsunami Information
Center
National Oceanic
and Atmospheric
Administration
UNESCO/IOC-NOAA
International Tsunami Information Center
[email protected]
NOAA Pacific Tsunami Warning Center
[email protected]
ITP-HAWAII 2010
30 August – 10 September 2010
Module: Tsunami Science and Hazard
Enabling Learning Objectives (ELO)
At the conclusion of this module, participants will be able to:
2-1
Explain what a tsunami is (generation, wave characteristics, occurrence)
2-2
Explain differences between local and distant tsunamis
2-3
Discuss what scientists learn from historic records (written accounts, data observations)
2-4
Discuss the importance of indigenous knowledge in tsunami preparedness
2-5
Learn the purpose, scope and goals of tsunami numerical modeling
Reference List
Atwater, B. F. et al. Surviving a tsunami—lessons from Chile, Hawaii, and Japan. US Geol. Surv. Circ., 1187 (1999).
Atwater, Brian F., Musumi-Rokkaku Satoko, et al. (2005). The Orphan Tsunami of 1700. (No. 1707). Seattle, WA: U.S. Geological
Survey, http://pubs.usgs.gov/pp/pp1707/
Cascadia Subduction Zone Earthquakes: A magnitude 9.0 earthquake scenario, CREW, 2005, http://www.CREW.org
Department of Earth and Space Sciences, University of Washington. http://www.ess.washington.edu/tsunami/index.html.
Gonzalez, F. I. Tsunami!, Scientific American, 280(5), 56-65, 1999, http://www.pmel.noaa.gov/pubs/outstand/gonz2088/gonz2088.shtml
Jansa, A., Monserrat, S., and Gomis, D.: The rissaga of 15 June 2006 in Ciutadella (Menorca), a meteorological tsunami, Adv.
Geosci., 12, 1–4, 2007, http://www.adv-geosci.net/12/1/2007/.
Kong, L. Big Waves: Tracking Deadly Tsunamis, Oceanography Special Report in 2004 Science Year, The World Book Annual
Science Supplement, World Book, Inc, 2003
National Geophysical Data Center Historical Tsunami Database: http://www.ngdc.noaa.gov/hazard/tsu.shtml
Reagan, Albert. B. and L.V.W. Walters, 1933,Thunderbird, p. 320, IN Tales from the Hoh and Quileute, The Journal of American
Folk-lore, Vol. 46, No. 182, pp. 297-346.
Reagan, A.B., 1934, A Hoh version of the Thunderbird Myth, IN Myths of the Hoh and Quileute Indians, Utah Academy of Sciences,
Vol. 11, pp. 17-37.
Reagan, Albert. B. and L.V.W. Walters, 1933, Thunderbird fights Mimlos-Whale, IN Tales from the Hoh and Quileute, The Journal of
American Folk-lore, Vol. 46, No. 182, pp. 297-346.
Tang, L., C. Chamberlin, and V.V. Titov (2008): Developing tsunami forecast inundation models for Hawaii: Procedures and testing.
NOAA Tech. Memo. OAR PMEL-141, 46 pp.
Titov, V.V., F.I. González, H.O. Mofjeld, and A.J. Venturato (2003): NOAA TIME Seattle Tsunami Mapping Project: Procedures, data
sources, and products. NOAA Tech. Memo. OAR PMEL-124, NTIS: PB2004-101635, 21 pp
UNESCO/IOC ITIC, Tsunami Glossary 2008, Intergovernmental Oceanographic Commission, Paris, UNESCO. IOC Technical
Series, 85, 2008
UNESCO/IOC ITIC, Tsunami, The Great Waves, Revised Edition, Intergovernmental Oceanographic Commission, Paris, UNESCO,
16 pp., illus. IOC Brochure 2008-1, 2008, http://ioc3.unesco.org/itic/files/great_waves_en_2006_small.pdf
Usapdin, T.P., A. Soemantri, and V. Agustin, The story that saved the lives of the people of Simeuleu, Indonesia, December 19,
2005, http://www.ifrc.org/docs/News/05/05121901/index.asp
Venturato, A.J., D. Arcas, and U. Kânoğlu (2007): Modeling tsunami inundation from a Cascadia subduction zone earthquake for
Long Beach and Ocean Shores, Washington. NOAA Tech. Memo. OAR PMEL-137, NOAA/Pacific Marine Environmental
Laboratory, Seattle, WA, 26 pp.
Yogaswara, H. and E. Yulianto. Smong, pengetahuan lokal Pulau Simeulue: sejarah dan kesinambungannya [Smong: Local
knowledge at Simeulue Island; history and its transmission from one generation to the next] 69 p. (Lembaga Ilmu Pengetahuan
Indonesia; UNESCO and and International Strategy for Disaster Reduction, Jakarta, 2006); http://www.jtic.org/en/infosources/jtic-info-sources/publications.html
Yulianto, E., F. Kusmayanto, N. Supriyatna, and M. Dirhamsyah, Where the First Wave Arrives in Minutes, Indonesian Lessons on
Surviving Tsunamis near Their Sources, UNESCO IOC Brochure 2010-4, 36 pp, http://www.jtic.org/en/info-sources/ jtic-infosources/publications.html?download=1317%3Awhere-the-first-wave-arrives-in-minutes
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Slide. What is a Tsunami?
Slide. What is a tsunami?
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Slide. What is a tsunami?
•
•
•
•
•
•
Stress:
In deep ocean, the wave-lengths can be great, while wave heights may only be
centimeters on the surface
Wave lengths are longer in deep ocean, shorter near shore
Wave period: crests every 10 minutes to 1 hour
First wave may not be largest. Tsunami generates series of waves which grow
as they approach the shore. Largest wave may be the fourth or fifth wave
Will quickly inundate coastal areas
Tsunamis are not connected to tides
Key Point. Tsunamis are a series of traveling waves of extremely long wavelength
and time period. They are generated when an entire column of water is suddenly
moved vertically, such as by the occurrence of a great earthquake.
Key Point. As tsunamis move from the deep ocean to shallow water, they slow
down and can grow in height, making them dangerous when they hit the coast.
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Tsunami derives from the Japanese term meaning wave (“nami”) in a harbor
(“tsu”). It refers to a series of traveling waves of extremely long length and
period, usually generated by disturbances associated with earthquakes occurring
below or near the ocean floor (also called seismic sea wave and, incorrectly, tidal
wave). Volcanic eruptions, submarine landslides, and coastal rock falls can also
generate tsunamis, as can a large meteorite impacting the ocean. These waves
may reach enormous dimensions and travel across entire ocean basins with little
loss of energy. They proceed as ordinary gravity waves with a typical period
between 10 and 60 minutes. Wave period is the time it takes two successive
waves to pass by. Their speed depends on the depth of the water. In the deep
ocean, tsunami waves propagate with a speed exceeding 1000 kilometers per
hour ([km], ~400-500 miles per hour).
The energy in a tsunami wave is spread out fairly evenly throughout the water
column. If a wave begins in the deep ocean, it may have a wave height of
several centimeters (1 foot [ft]) or less) and will not be detected by ships due to
its long wave period. Tsunami wavelengths are hundreds of times greater in size
when compared to ocean depth. Wavelength is the distance between two
consecutive waves.
Tsunami wave shape changes as it approaches shore because decreasing water
depth increases wave height and decreases wavelength.
Tsunami waves are distinguished from ordinary ocean waves by their great
wavelengths (often exceeding a 100 km or 60 miles [mi] or more in the deep
ocean), and by their longer wave periods (ranging from 10-60 minutes). As they
reach the shallow waters of the coast, the waves slow down and the water can
pile up into a wall of destruction tens of meters (30 ft) or more in height,
inundating low-lying areas. Waves can be amplified where a bay, harbor or
lagoon funnels the wave as it moves inland. Large tsunamis have been known to
rise over 30 meters (100 ft). Even a tsunami 3 to 6 meters (10-20 ft) high can be
very destructive and cause many deaths and injuries.
Tsunamis have no connection with tides; the popular name, tidal wave, is entirely
misleading.
Tsunami waves are often no taller than normal wind waves, such as surfing
waves, but they are much more dangerous. Tsunamis can flow inland for tens of
minutes while wind waves flow inland for tens of seconds. Tsunamis can create
strong currents. Therefore, even a small tsunami can be dangerous.
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Slide. What does a tsunami look like?
Slide. What does a tsunami look like?
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Tsunamis have physical characteristics that are very different from ocean swells
and surfing waves. The videos show examples of actual tsunamis on December
26, 2004 that struck the coasts of Indonesia 30 to 45 minutes after the
earthquake, and the coast of Thailand ~3 hours. Television news in Banda
Aceh, Sumatra, Indonesia, and tourists vacationing at Patong Beach, Thailand
captured vivid images of the tsunami’s arrival and devastation.
The first arrivals are seen in Thailand as a thunderous wall of water that
immediately floods inland. The wave forces and currents are so strong and
turbid that people can easily be swept off their feet where they can drown
quickly or be thrown against buildings or trees and lose consciousness. As
successive waves enter a city or village, streets can become river channels for
floating debris.
Tsunami waves can arrive for hours, with each receding wave pulling debris out
to sea, followed by an advancing wave that picks up the same debris and more,
and re-deposits it inland. Floating debris become, in essence, battering rams
causing more damage as they strike whatever is in their way. Each wave
scours and erodes coastlines and building foundations, but also deposits a layer
of sand and mud when it hits shore. Secondary impacts caused by wave
breakage include fires and HAZMAT spills when power, utility, or resource lines
are severed. In 1993 in Okushiri, Japan, fires broke out when gas lines broke
during the onslaught of tsunami waves. While many heeded natural warning
signs and siren alerts and evacuated that evening, fire razed the homes of many
citizens in the lowland town of Aonae, Japan.
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Visual examples include:
1995, Mexico tsunami. Tsunami
waves recede seaward exposing
the ocean bottom. Stories of people
collecting fish during the ocean
drawdown, unaware that another
tsunami was on it way, have been
reported.
C. Snyolakis, University of Southern California
1983, Japan Sea tsunami. Tsunami
arrives as a flood of water.
Tokai University
1964, Aleutian Islands, Alaska
tsunami arriving at Hilo, Hawaii.
Tsunami waves arrive as walls of
water. They do not break and curl
making them impossible to surf.
Pacific Tsunami Museum
2004 Indian Ocean tsunami. Aerial
photo of tsunami wave receding, Sri
Lanka. Complex eddies can form
seaward of the wave front.
DigitalGlobe
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Slide. What does a tsunami do?
Slide. What does a tsunami do?
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1. Top Video - Images of before and after shows how
tsunami deposits mud and sediment over the land and
covers structures.
2. Bottom Video - Images illustrate sea current as tsunami
wave recedes seaward carrying floating debris.
Before and after pictures of Banda Aceh, Sumatra, Indonesia, following the
December 26, 2004 tsunami show how a tsunami wave will flood all low-lying
areas, leveling structures, flattening trees, and depositing a layer of mud
everywhere it flows.
Video vividly captures the tsunami wave on September 29, 2009 as it recedes
carrying floating debris seaward. Dangerous advancing and receding tsunami
waves occurred every 5 to 10 minutes for about 2 hours before wave heights
subsided.
Slide. How often do tsunamis occur?
•
1900 – 2009
o ~ 1 fatal tsunami/yr
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Slide. Where do tsunamis occur?
•
•
•
•
Stress:
Each red dot indicates tsunamis that have occurred in the past 4,000 years
A closer look at the maps on slide 2-10 makes it obvious that most tsunamis are
local or regional
Fewer are distant tsunamis, which are tsunamis that will have impact far away
This history should make it obvious that it is very important to prepare for local
and regional tsunamis
Subduction zones cause large earthquakes which are the most likely to generate
tsunamis. These subduction zones are characterized by deep ocean trenches.
The volcanic mountain chains that comprise “The Ring of Fire” are strewn across
the Pacific’s many subduction zones.
84% of the world's tsunamis were caused by earthquakes (large/great
earthquakes or earthquake-induced landslides) and over 73% of these were
observed in the Pacific where large earthquakes occur as tectonic plates are
subducted along the Pacific Ring of Fire.
Local tsunamis are defined as tsunamis that impact coasts within about one hour.
Regional tsunamis are defined as tsunamis that impact coasts within one to three
hours.
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Distant, or teletsunamis are defined as tsunamis that impact coasts more than
1000 km (450 miles) from the tsunami source. They can take hours to more than
one day to arrive.
Notes:
Top image: Epicenters of all tsunamigenic earthquakes. Tsunamis have caused
damage locally in all ocean basins. There have been more than 2,000 observed
with ~1,100 confirmed over the past 4,000 years. Of those confirmed as
tsunamis, 73% Pacific, 14% Mediterranean, 6% Caribbean/Atlantic, 5% Indian,
2% Black Sea.
Middle image: Locations of earthquakes, volcanic eruptions, and landslides
generating tsunamis that caused damage or casualties locally. Most tsunamis
are local or regional tsunamis.
Over the last 35 years (1975-2009), 52 tsunamis (35 with deaths) have occurred.
Bottom image: Source locations of teletsunamis causing damage or casualties.
10% of confirmed historical tsunamis cause damage or casualties at far
distances. Over the last 200 years, there have been 26 teletsunamis (9 with
deaths). While the majority of destructive teletsunamis were generated by
earthquakes in the Pacific, teletsunamis have also caused damage and
casualties in the Indian and Atlantic oceans.
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Slide 2-11. How are tsunamis generated?
Slide 2-11 has an embedded video which starts automatically and loops.
Describe the tsunami generation process by an earthquake:
• Plate “subducts” (one tectonic plate is pushed downward beneath another)
generating an earthquake
• The earthquake faulting pushes the ocean column above it, creating a
tsunami wave
• The tsunami wave spread out all directions
84% of tsunamis are generated by earthquake sources. 14% are generated by
earthquake-triggered landslides. 1% are generated by volcanic activities and 1%
are caused by other sources.
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Earthquakes:
Tsunamis are most often generated by displacement of water resulting from
shallow, undersea earthquakes. The shallower the earthquake is beneath the
seafloor, the greater the likelihood that a large earthquake can generated a
tsunami - these are earthquakes at depths less than 100 km (45 miles) or which
rupture the seafloor. However, most undersea earthquakes do not generate
tsunamis. Based on historical records, earthquakes with magnitude greater than
6.5 have potential to generate tsunamis. The large earthquakes occur along the
subduction zones, such as the Pacific “Ring of Fire.” In subduction zones, the
most common earthquake type is called a thrust, or reverse, fault where one
tectonic plate is pushed upward over the adjacent plate. Less common in
subduction zones are normal faults, where one tectonic plate drops down with
respect to the other plate.
Landslides:
Tsunamis can be generated by displacement of water resulting from rock or ice
falls, underwater landslides, or slumps. They can originate either on land and
enter the ocean, or be confined only to the undersea. Such events can be
induced naturally (e.g., erosion, earthquakes, gravity, volcanic eruption, etc.) or
by humans (e.g., excavation and earthwork).
Volcanic Activity:
Tsunami waves can be generated by displacement of water caused by: (1)
volcanic eruption and ensuing collapse of magma chamber(s) at the summit or
on the flanks, (2) massive flows of volcanic debris, or subaerial landslides that
enter the ocean, or (3) underwater volcano collapse.
Atmospheric/Meteorological:
Tsunamis can be generated by sudden changes in atmospheric pressure over
the ocean that travel at the same speed as the ocean wave.
NOTE: Not all researchers believe that meteorological tsunamis, sometimes
called rissaga, meet the technical definition of tsunami since they are not
generated by a sudden impulse.
Meteor Impact:
Besides the Chicxulub (or Brazos River, Texas) event, limited evidence exists
regarding a meteor/asteroid-induced tsunami. However, the scientific community
believes the impact of a massive meteor/asteroid could displace enough water to
generate a sizeable tsunami.
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Slide. How fast? Local tsunamis
Stress:
• Local tsunamis will arrive in minutes. (In the recent example of American
Samoa, the tsunami wave arrived in 10 to 15 minutes)
• In a local tsunami you will very likely feel the ground shaking from the
earthquake. This may cause building damage. The response is to duck,
cover, and hold first, then to find higher ground
• You may see changes in both the level of the land (due to the earthquake) and
sea (due to the tsunami)
In addition to local earthquakes, landslides originating above or below water are
also possible sources of local tsunamis. Smaller-sized earthquakes can also
trigger underwater landslides, which in turn could generate a tsunami.
Key Point: During a local tsunami generated by an earthquake, strong ground
shaking serves as a natural warning. Other natural tsunami warning signs are
rapid or unusual sea level changes, such as a receding wave, and a loud roar
like a train or airplane. Immediate self-evacuation to high ground and inland
should begin after natural warning. Follow evacuation route signs to the
assembly area(s).
Earthquake rupture may also cause land deformation and/or subsidence (drop
down or uplift) which could allow sea water to immediately flood low-lying areas
ahead of the tsunami. These land level changes can be long term.
Local source tsunamis are more frequent than distant source tsunamis. Their
impacts are confined to areas near the source where runups can be extremely
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high. In 1975, a local tsunami off Hawaii island caused by a magnitude 7.2
offshore earthquake generated local runups as high as 47 feet, but this tsunami
did not affect other coastlines of Hawaii island or Honolulu on the main island of
Oahu which is about 250 km to the northwest.
Slide. How fast? Distant tsunamis
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Slide. How fast? Distant tsunamis
Stress:
• A distant tsunami can take hours to arrive
• The 1960 earthquake in Chile created a tsunami which hit locally in minutes, then in
Hawaii 15 hours after the earthquake, and hit Japan 22 hours after
• The tsunami caused destruction and death in Chile, Hawaii, and Japan
Slide shows the Pacific Ocean and the locations of tectonic plates (color blocks),
subduction zones (red line), and tsunami travel times (1-hour contour intervals) for the
1960 Chile tsunami.
Key Point: For a distant tsunami, the public will not be able to feel the earthquake
shaking because it is located far away. In this case, communities will rely on Tsunami
Warning Centers to provide information on the tsunami threat to state and local officials
who will then decide whether to evacuate or issue an “all clear” after an evacuation.
For distant tsunamis, official information will precede the arrival of the first tsunami
wave. Because there is time before the first wave arrives (sometimes many hours),
unofficial information becomes readily available, and this often provides challenges to
authorities and confusion to the public since conflicting or misleading interpretation is
possible.
Key Point: A distant destructive tsunami is usually also locally destructive. For
example in the 1960 Chile earthquake, tsunami waves struck the Chilean coast within
minutes after the earthquake In addition, waves also propagated as a destructive
teletsunami across the Pacific Ocean. It took more than 14 hrs to reach Hawaii where
it killed 61 people across the State, and 22 hours to reach Japan where more than 120
people perished. The 1960 tsunami, and the damage and deaths that it caused, was
the catalyst for the start of the international tsunami warning system in 1965.
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Slide. Assessing the tsunami hazard
Oral and written records complement tsunami scientists’ existing tools
of modern science and technology in identifying hazardous events.
Along with modern scientific tsunami numerical modeling, they provide
information for communities to determine their level of risk. Local
knowledge can also supplement scientific data and help educate the
population about impending hazards. Consequently, lives may be
saved by oral history and written records.
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Slide. Historic Records
Hint: The written records referred to here are the handwritten or
printed materials prior to the use of instruments to record tsunami
data. Some records such as from Japan date back to 600 A.D. The
World Data Center for Tsunamis serves as the official archive for
tsunamis. Historical databases provide one means for assessing the
tsunami hazard.
Investigating written records (e.g., 19th century news clippings and
reports) can provide information about previously unknown events.
Example. In 1700 A.D. a large tsunami was generated on the Cascadia
subduction zone. Though no written record exists from the U.S. from this time
period, the tsunami struck the Japanese coast (distant tsunami). Japanese
records allowed scientists to confirm and refine knowledge (size and timing)
about the 1700 Cascadia Subduction Zone earthquake and tsunami event.
Participant Note: Internet databases can serve as resources to corroborate
written and oral histories. The world’s authoritative tsunami archive is the World
Data Center for Tsunamis (WDC-Tsunamis), which is co-located with NOAA
National Geophysical Data Center (NGDC) in Boulder, CO. The database
contains
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summaries of tsunami events for the past 4000 years, and data observations of
tsunami wave heights, runups, inundations, casualties, damages, and other
important information.
The International Tsunami Information Center (ITIC) works with the WDC/NGDC
to collect tsunami event data for archiving. An historical database is available
online at http://www.ngdc.noaa.gov/hazard/tsu.shtml and as an offline GIS tool
known as TsuDig.
Slide. Geologic Record - Paleotsunamis
Stress: The geologic record can give evidence from thousands, and perhaps
millions of years ago.
• By digging a trench and examining the sediment layers, you can discover
evidence of past tsunamis
• In the illustration, the lighter layers are representative of tsunamis. If you
date these layers, you can get information on when the tsunamis occurred
• This information helps in assessing the tsunami hazard in a given area
Paleotsunami studies are used to extend the historical record back in time.
Tsunami deposits can be preserved in the geologic record providing evidence of
past tsunamis. These records help determine magnitude and frequency of
tsunamis.
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Example. Here a Native American fire pit was built in a coastal sand dune. In
1700 A.D. a tsunami struck the coast leaving behind the dark sand layer. In large
earthquakes, the level of land relative to sea level can change. In this case, the
land went down or subsided. The subsidence is why tideflat (marine) mud was
deposited on top of the tsunami deposit.
By digging trenches and looking for recurring tsunami sediment layers and
determining the dates of the deposit, scientists can estimate the recurrence
interval of large tsunamis. Knowing the frequency helps officials to assess the
tsunami hazard.
Slide. Geologic Record - Paleotsunamis
Example: Image: Thick sand layers at left represent the 1960 Chilean
tsunami and three of its predecessors. Their setting is a Chilean lowland
midway along the nearly 1,000-km length of the 1960 fault rupture (a break
that generated the 20th century’s largest earthquake, of magnitude 9.5).
The layers probably mark the site’s four greatest tsunamis of the last 1000
years. These exclude a tsunami in 1837 that probably originated further
south. The 1837 tsunami, like the 1960 event, caused deaths in Hawaii.
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Slide. Indigenous Knowledge – Folklore and Oral Traditions
Hint: Stress that although this source of information is not as accurate as
scientific data, it does provide knowledge of past events. The process of
passing information from generation to generation also helps sustain
preparedness.
Indigenous knowledge based on folk stories, songs, and other cultural practices
that have been learned and taught especially to children, play an important role in
sustaining awareness through generations.
This information can also assist a community in determining level of tsunami risk
since past events are recounted. Although not accurate or precise when
compared to modern scientific numerical modeling, oral traditions and past
experiences are useful for an immediate assessment. For communities, local
knowledge, wisdom and experience are powerful and crucial for educating the
population about its tsunami hazard.
Example. Oral traditions of Cascadia’s native peoples tell of flooding from the
sea. Stories of the Hoh and Quileute Indians of the northwestern Olympic
Peninsula relate the epic struggle between Thunderbird and Whale. Thunderbird
is a bird of monstrous size, "when he opens and shuts his eyes he makes
lightning. The flapping of his wings makes the thunder and the great winds."
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"Thunderbird ... soared from her dark hole in the mountains....far out over the
placid waters and there poised herself high up in the air and waited for [Whale] to
come to the surface of the water … the powerful bird darted and seized it. 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 were ... a shaking, jumping up and trembling of the earth beneath, and a
rolling up of the great waters. The waters receded ... and ... again rose.”
These stories were captured in a children’s video, Run to High Ground, produced
by the Hoh Tribe in cooperation with the Washington Emergency Management
Division. The video is an example of a Native American folktale that now serves
as an educational tool on tsunamis and what to do when the earth shakes.
Slide. Risk Assessment
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Slide. Tsunami Modeling – Why?
A tsunami model provides computer simulations of hypothetical and past tsunami
events. Since tsunamis are infrequent, models of credible or worst-case
scenarios can assist in understanding the tsunami hazard for a particular
community or region. Types of models include:
•
• Propagation models: run at a relatively low resolution to model a tsunami as it
travels across an ocean basin; it does not take into account runup (flooding onto
land). A propagation model allows you to estimate how long it will take a tsunami
wave to arrive, and what the wave heights are expected to be at a location
offshore in deeper water (10-50 m water depth).
Tsunami energy plots can be derived from modeling that will be useful for
warning centers, emergency management agencies, and other decision-makers
responsible for public safety. These plots show the regions of greater tsunami
energy and therefore higher expected wave amplitudes. The plots are highly
dependent on where earthquake source is located, and its extent and direction of
fault rupture, so that a small change in location of the earthquake can result in a
vastly different energy plot.
This map is useful because it provides information on the directions of higher
tsunami energy. Islands or coasts that are high-energy targets are likely to have
even higher coastal waves heights because the shoaling of the sea floor acts to
increase tsunami wave heights.
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September 2010
Examples:
In the map above, calculated tsunami maximum deep-ocean tsunami amplitudes
(tsunami wave forecast) are shown for the Pacific from a M9.0 Shumagin Gap
earthquake that generates a tsunami that crosses the Pacific. Coastal
amplitudes would be significantly larger than the predicted offshore amplitudes.
In the map above, calculated tsunami maximum deep-ocean tsunami amplitudes
are shown for the Caribbean and Atlantic from a M8.6 Puerto Rico Trench
earthquake that generates a tsunami that propagates into the northeast Atlantic.
Coastal amplitudes would be significantly larger than the predicted offshore
amplitudes.
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• Inundation models: run at a higher resolution to estimate the tsunami runup and
inundation onto land. The output of a propagation model is often used as the
input to the inundation model.
Models, which are science products, are then interpreted by communities
interested in assessing their risk to tsunamis.
Slide. Modeling to Evacuation Map
Stress that one of the most important contributions of modeling is that it
provides estimates of a tsunami’s hazard. This information helps decisionmakers and communities create effective evacuation maps and routes. Models
provide information on, for example, the expected inundation and maximum
water currents. From these, a community’s hazard exposure can be assessed
and response plans developed.
Predicting, or forecasting when and where the next coastal earthquake and
tsunami will strike is currently impossible. However, once a tsunami is confirmed
to be generated, forecasting a tsunami’s arrival and impact is possible through
modeling and measurement technologies.
(http://www.tsunami.noaa.gov/tsunami_story.html)
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STRENGTHENING TSUNAMI WARNING AND EMERGENCY RESPONSE
September 2010
Example: In this example from Long Beach, Washington, the input scenarios
are those judged to be most likely, or most dangerous to the community if they
were to occur. The model results are summarized as an inundation map
showing the maximum wave heights. In addition, maximum wave currents are
outputs of a modeling effort. Tsunami wave model results showing propagation
and inundation of the coast can also be animated.
Model results include the expected inundation and maximum water currents.
They are used by communities to develop their evacuation maps. Inundation
modeling is a valuable hazard assessment tool that assists communities in
determining their exposure to tsunamis, and then in planning how to minimize
that risk.
Slide. Summary
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