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Tsunami Basics. What Mariners should consider. Brought to you by the National Weather Service
located in Monterey California.
A Distantly Generated Tsunami Has Occurred. What do you do?
Although time is of the essence don’t panic. Depending on the location of the tsunami generating
earthquake you could have up to 10 hours to prepare.
Listen for official messages from the NWS. Is it a Watch, Warning or an Advisory?
Listen to what your emergency management officials are saying and heed their recommendations.
Respond to your local emergency management official’s recommendations. You may be advised
to seek safe harbor in deep water or you may be advised to evacuate to higher ground.
The NWS issues four types of tsunami messages. The initial message may be a Tsunami watch
which means that an earthquake has occurred that may result in a tsunami. Stay tuned for
more information. If a tsunami is generated and widespread inundation
of land is imminent or occurring a Tsunami warning will be issued. Please evacuate to
higher ground. A tsunami advisory is issued when a tsunami
has been generated but little to no inundation of the land is expected. However, strong currents
are imminent or occurring. Please move away from the shore, harbors and marinas.
Finally the Tsunami information statement is a heads up to let you know that a distant
event has occurred and we are looking into it. No action is required at this point
An earthquake has occurred near your location and has generated a tsunami. What do you do?
In this case Mother Nature will provide you with the tsunami warning. The first sign will
be the vigorous shaking of the earthquake. Protect yourself by crawling under a sturdy
table or desk. Stay under this shelter holding on until the shaking has ceased. Remain under
cover for at least 20 seconds after the shaking has ceased.
If by the water look for a rapid withdraw of water from the beach and listen to the
ocean. You may hear the ocean rumbling louder than usual.
Respond. If you are on land or tied at dock leave you boat! You may not have time to save
it. Walk or run quickly to higher ground. Remember in most cases you only need to move
20 feet above sea level to find safety from the tsunami.
If you are on the water near shore and you can reach shore within 10 minutes do so, this
is your best bet. Once on shore abandon ship and head for higher ground.
If you are on the water and it is not possible to make it to shore quickly head towards deep
water. The rule of thumb is, safety can be found at a water depth of 100 fathoms.
Potential impacts at harbors. During a tsunami warning deep water wave heights
could exceed 3 feet. This translates into a large long lasting rise of surging water
and inundation of dry land. This will also result in extremely strong currents in open
water and in harbors. Although the open water wave height will not
be as large during a tsunami advisory, only 1 to 3 feet, still expect strong currents
in open waters as well as in harbors and ports.
The release of energy as the tsunami wave enters the shallow water of ports and harbors
is tremendous. This release of energy will result in damage to boardwalks, docks and
boats. Strong currents associated with the tsunami waves will undermine moorings, rip
boats from moorings and damage docks. Extreme tidal variations can sink boats moored in
shallow water. Extreme low water can result in boats bottoming out especially keel boats.
Deciding whether or not to take your boat off shore.
The rule of thumb for safe water depth is 100 fathoms
Be sure to ask yourself the following: How big is the tsunami
How much time do I have Am I capable of navigating offshore
Is my boat prepared to spend 48 hours offshore What about the weather and sea conditions
Remind yourself: There will be strong currents
The maybe rogue waves You may have to remain offshore for some time
Most importantly be prepared! Know your vessels capabilities
Know your own capabilities Know the distance and how long it takes to
get to deep water Know the offshore weather and sea conditions
Have enough fuel, fresh water and food Have a plan
Keep extra fenders around if you plan to stay in harbor.
In summary if a distantly generated tsunami occurs don’t panic, stay calm you have some
time to prepare. Listen for official messages from the national weather service. Listen
to what your local emergency management officials are saying and heed there recommendations.
Finally respond by listening to your local emergency officials and heed their recommendations
even if it means leaving your boat!
Remember if a local tsunami is generated, listen to Mother Nature, the earthquake will
be your first warning. Respond accordingly, if at the harbor leave your boats and head
to higher ground, if in the water heading to deep water may be your best bet.
Remember to always be prepared and know the
weather and sea conditions before you go.
Here are some links to additional information about tsunamis
Special thanks to the California Emergency Management Agency and the California Geological
Survey
For local weather and tsunami information please visit us via the web, facebook, youtube
and twitter. As always you can give us a call at 831-656-1725 .