Wednesday, 9 December 2015

Making (tracks from) Waves: Tsunami Preparedness

I have previously written about the capacity of earthquakes to strike without warning and in unexpected places.  A similar hazard comes from a related phenomenon: tsunami.
Tsunamis, as is well known, are significant waves produced by undersea disturbances, including earthquakes and land- or mudslides.  The damage they produce can range from strong currents, broken boat moorings and minor inundation (as affected New South Wales following the 1960 Chilean earthquake) to catastrophic mass casualty events.  The potential effects of a tsunami in any given area are impossible to predict, given the variables of the cause, surrounding geography and degree of warning.  For example, a tsunami caused by an undersea landslide in the Gulf of Mexico might be expected to cause a surge of water like that associated with Hurricane Katrina and affect low-lying coastal Louisiana significantly in a way that might not occur elsewhere.

Gulf of Mexico landslide zones.png
Image from here

The potentially catastrophic effects of tsunami means preparation and awareness are important.
Preparing for a tsunami
A number of government agencies now monitor for tsunami activity.  Americans may wish to consult the warning website operated by the National Weather Service.  Australians should consult that established by the Joint Australian Tsunami Warning Centre.

Image from here

As with earthquakes and severe storms, the best form of long term preparation is to prepare an evacuation kit and to have considered where you might go if evacuation is recommended.  If you decide to evacuate, the Texas Department of Public Safety stresses driving inland and not parallel to the coast.

During a tsunami
Natural events – including feeling a strong earthquake, noticing a rapid rise or fall in coastal waters or hearing a loud roaring sound from the ocean – may be an indication that a tsunami is imminent.
Image from here
The Victorian State Emergency Service is responsible for that jurisdiction’s preparation.  It recommends that, if the wave is likely to affect mainly the marine environment, people should leave the water and move away from the water's edge.  Sailors who are able to should return to shore, although boats which are at sea should remain in deep water (if you have not already done so, put on a life jacket).  Where it is expected that land will be flooded, it is recommended that people move at least a kilometer away from the water and to a point at least 10 metres above sea level.  If this is not possible, seek shelter on the upper levels of a brick or concrete building.
Remaining in the area of a tsunami is significantly dangerous: fifteen centimetres of fast-flowing water is enough to knock over an adult; less than a metre of fast-flowing water can carry away a car. 
After a tsunami
After a tsunami has occurred, the US Department of Homeland Security recommends  avoiding the affected area until you are advised by the authorities that it is safe to return: there may be a series of waves after the first one.  Give assistance where you are able, but advise the relevant authorities if you become aware of a person needing rescue.  Be cautious when re-entering buildings as they may have sustained significant structural damage and be at risk of collapse.

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