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Tsunami Messaging Project


These are notes following the webinar-enabled discussion held December 19, 2013, about the definition of a tsunami and the causes of a tsunami.

Participants on this webinar are listed at the bottom of this page.

1. Definition of a tsunami

Rocky showed a list of definitions of a tsunami culled from various print and web-based documents listed here (this is a link.)

Rocky then showed a shorter list of definitions of a tsunami that a similar group arrived at in February, 2012. That list is here (this is a link).

Rocky reviewed the objective is to try to find agreement among stakeholders (Government at all levels, Tribal organizations, NGOs, cooperative work groups (such as RCTWG), media, and private organizations) so that a suggested list of source information that can be adopted by others for ongoing dissemination can be developed. This is not to create a “this is the only message” list, but rather, a list of messages vetted through knowledgable people and grounded in research and science. Such grounding helps reduce the use of folklore and myths.

We also need to be sensitive that some people understand technical information differently. This can be reflected, partially, by doing a reading level index, but is more complex than that. We should strive to reach as broad a general audience as possible.

Raw discussion notes:

* What characterizes a tsunami is the time or distance between crests.

* Perhaps we go with something more simple because it is understandable for the general audience

* What makes a tsunami different from weather … it is a shallow wave

* A tsunami flows over the land like a river.

* Concern that water comes along shorelines.

* A tsunami looks different in different situations. Flowing over land or a fast-rising flood have been used.

* The word “surge” is very weather-like. Also, if talk about surges, we've lost some people.

* Okay to use word “wave” w/o having to use the technical terms like wavelength.

* We should address periodic nature in the definition.

* “The surges last for minutes, hours, or even days” – what do we mean by that? The whole event or individual surges?

* How about, “the waves can keep coming for hours and days”

* Definition needs to differentiate why a tsunami is different from a wind wave or storm surge.

* Definition and cause are closely linked.

* A tsunami is (most often) (generally) a series of earthquake-generated waves that can cause (destructive) (catastrophic) (extreme) (damaging) flooding along shorelines and areas well inland.

* Concern that a tsunami is not always generated by an earthquake. Other causes of tsunamis are very rare.

* Volume of adjectives and concepts is a concern.

* Ensure that any time we use any of these simple descriptions, we should let them know that more information is available.

2. Causes of a tsunami

Rocky showed a list of causes of a tsunami culled from various print and web-based documents. That is is here (this is a link).

Raw notes from discussion:

* A tsunami is usually caused by an earthquake under the sea floor.

* A tsunami is caused by a vertical displacement under the sea floor.

* Using the term 'vertical displacement' helps differentiate which earthquakes cause a tsunami and which do not.

* When a large amount of ocean water suddenly moves up and down, a tsunami can be the result.

* A tsunami is the vertical displacement of the entire water column of the (entire) ocean.

* The motion of the water from a wind wave is confined to a relatively shallow depth beneath the ocean's surface. A tsunami means the energy of the wave goes through the entire depth of the ocean.

* A tsunami moved the entire thickness of the water from the bottom to the surface.

* A tsunami is the sudden (uplift) (vertical rise) of the sea surface usually caused by an earthquake, volcanic activity, undersea landslide, etc.

* Note – this is the “gee-whiz” element – the entire ocean column moves.

* How do you explain that some tsunamis in the open ocean are not detectable?

* Need to “unteach” the “wall of water.”

* Stay away from talking about the sea surface only. We're talking about a tremendous amount of energy traveling through the entire ocean.

* Think about using terms that include “force” or “energy”

* Energy in the water that could develop into different actions when it reaches the coast. (Put all of this energy in the ocean and this is what happens.)

* We must consider who the audience is – very hard-pressed to come up with a “one definition fits all.”

Next steps

Considering the notes above, please suggest what YOU think would be a definition of a tsunami and wording for the cause(s) of a tsunami using the discussion section below. (Scroll down.)

12/19/2013 webinar participants

Nicolas Arcos Honolulu HI ITIC
Melinda Bailey Ft. Worth TX NWS Southern Region
Ted Buehner Seattle WA NWSFO, Seattle
Gerard Fryer Ewa Beach HI NWS/Pacific Tsunami Warn Ctr
Wildaomaris Gonzalez Mayaguez PR Red Sismica
Jeanne Johnston Kailua HI DPS, Inc.
Kate Long Pasadena CA Cal OES
Rocky Lopes Silver Spring MD NWS HQ Tsunami Program
Jeff Lorens Salt Lake City UT NWS Western Region
Teron Moore Victoria BC EMBC
Alina Nieves Corpus Christi TX NWSFO, Corpus Christi
Sue Perry Pasadena CA USGS SAFRR Program
Ervin Petty JBER AK Alaska HSEM
Beth Pratt-Sitaula Ellensburg WA CWU - CEETEP
Cindi Preller Anchorage AK NWS Alaska Region
Cindy Pridmore Sacramento CA California Geological Survey
Kevin Richards Honolulu HI State Civil Defense
Althea Rizzo Salem OR OEM
Crista Stewart Crescent City CA Elk Valley Rancheria
Katherine Thompson New York NY Columbia University
Kerry Varkevisser Arcata CA Humboldt State University
Paul Whitmore Palmer AK NWS/NTWC
Walt Zaleski Fort Worth TX NWS Southern Region


Jeff Lorens, 2013/12/23 14:19 A tsunami is a series of waves in the ocean, most often caused by an earthquake which produces an uplift of the seafloor. The energy then spreads out horizontally and moves away from the source, eventually arriving at the coast and potentially causing damage from flooding and strong currents for many hours.

Nicolas Arcos, 2013/12/23 18:57 If a simple/short definition is desired for each,

Tsunami: A tsunami is a series of long period waves generated by a displacement of water. Tsunami waves can last hours or days. (Note: period is a term likely requiring further definition. Although one more term to define seems acceptable).

Causes of a tsunami: A tsunami is generated by large, sudden displacement of water.

I would add that the Tsunami Glossary (IOC Technical Series 85) should be considered as a reference for further (technical) information, as it has been accepted by the international community (including US). While the document is technical and not intended for general public, it is (I believe) the only Tsunami Glossary developed. Also, the Glossary has been accepted by UNESCO/IOC.

Tsunami Glossary:

Walt Zaleski, 2014/01/09 11:21 For simplicity to reach the masses, below are refinements of two statements from our last call:

Definition: A tsunami is most often a series of earthquake-generated waves which can produce catastrophic damage and extreme flooding along shorelines and areas well inland.

Cause: A tsunami is the sudden vertical rise of the sea surface usually caused by an earthquake, volcanic activity, or undersea landslide.

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messagenotes12192013.txt · Last modified: 2014/05/13 13:54 by christa