what are the dangers of tsunami?

Answer 1

A tsunami is a series of sea waves caused by a sudden event beneath or near the ocean. The following events can create a tsunami:

* an underwater earthquake
* a large underwater landslide
* coastal landslides into the sea
* volcanic eruptions beneath or near the sea
* in rare cases, a tsunami can be created by the impact of a meteor

Like a flood, the effects of a tsunami can vary greatly from one region to another but they pose a threat to property and life in all coastal areas.
The three types of tsunami

There are three distinct types of tsunami. The type you encounter depends on the distance you are from the place where it is generated.

* Distant tsunami are generated from a long way away, such as from across the Pacific in Chile. In this case, we will have more than three hours warning time for New Zealand.
* Regional tsunami are generated between one and three hours travel time away from their destination. An eruption from an underwater volcano in the Kermadec Trench, to the north of New Zealand, could generate a regional tsunami.
* Local tsunami are generated very close to New Zealand. This type of tsunami is very dangerous because we may only have a few minutes warning and damage could be quite significant in specific areas. A landslide in the Hikurangi Trench or a large earthquake from an offshore fault could cause a local tsunami

Tsunami warning

Here are the ways you will know that a tsunami is approaching.

* The Ministry of Civil Defence & Emergency Management will issue a national warning on the television and radio
* You will receive a warning from your local council or Civil Defence Emergency Management Group. Talk to them to find out how you will receive your warning
* If you are at the coast and you feel a strong earthquake, see the sea receding (the waterline moving away from the shore), the sea bubbling or making a roaring sound, move to higher ground immediately.
* Be aware that there may be more than one wave, sometimes as many as seven, and it may not be safe for up to 24 hours. The waves that follow the first one may also be bigger

Before a Tsunami

Getting ready before a tsunami strikes will help reduce damage to your home and business and help you survive.

* If you live in a coastal area, check with your council about the level of risk a tsunami would pose to you and your family
* Check with your local Civil Defence Emergency Management Group to find out what warning procedures you should expect
* Develop a Household Emergency Plan and ensure you have a Getaway Kit should you need to leave in a hurry
* If you are buying land, investing or building in a coastal area, talk to your council about the risks of a tsunami, coastal storm surge and erosion
* Know where the nearest high ground is and how you will reach it. Higher ground should be at least 35m above sea level or at least 1km inland. Plan your escape route now with your household

During a tsunami

* If you haven’t done so already, move immediately to the nearest higher ground.

After a tsunami

* Listen to the radio for civil defence advice
* Do not go down to the sea until you have been told it is safe to do so

Checklists

These checklists tell you what you need to do to get ready

Household Emergency Plan
Emergency Survival Kit
First Aid Kit
Getaway Kit
home | latest news | get ready | resources |

Answer 2

BIGGEST DANGER:

The Tsunami wave:

Ocean waves are normally divided into 3 groups, characterized by depth:

Deep water
Intermediate water
Shallow water
Even though a tsunami is generated in deep water (around 4000 m below mean sea level), tsunami waves are considered shallow-water waves. As the tsunami wave approaches the shallow waters of shore, its time period remains the same, but its wavelength decreases rapidly, thus causing the water to pile up to form tremendous crests, in an effect known as "shoaling".

:-)~

Answer 3

Well, think about New York city. High rise building would be ok because of todays new building plans, they can resist high winds so they are most likely to survive any kind of tsunami's. And the BIGGEST danger of a Tsunami would be drowning.

Answer 4

No watching a international map (flat one) you think of it would, yet surely a globe the tsunami is going threw incorrect way and hitting California threw Washington there having evacuations yet not lots injury because of the fact that its so far away

Answer 5

Often referred to as "tidal waves", a tsunami does not look like the popular impression of "a normal wave, only much bigger". Instead it looks rather like an endlessly onrushing tide which forces its way around and through any obstacle. Most of the damage is caused by the huge mass of water behind the initial wave front, as the height of the sea keeps rising fast and floods powerfully into the coastal area. The sheer weight of water is enough to pulverise objects in its path, often reducing buildings to their foundations and scouring exposed ground to the bedrock. Large objects such as ships and boulders can be carried several miles inland before the tsunami subsides.

Tsunamis act very differently from typical surf swells: they contain immense energy, propagate at high speeds and can travel great trans-oceanic distances with little overall energy loss. A tsunami can cause damage thousands of kilometres from its origin, so there may be several hours between its creation and its impact on a coast, arriving long after the seismic wave generated by the originating event arrives. Although the total or overall loss of energy is small, the total energy is spread over a larger and larger circumference as the wave travels. The energy per linear metre in the wave is proportional to the inverse of the distance from the source.[citation needed] (In other words, it decreases linearly with distance.) This is the two-dimensional equivalent of the inverse square law, which is followed by waves which propagate in three dimensions (in a sphere instead of a circle).

A single tsunami event may involve a series of waves of varying heights; so the set of waves is called a train. In open water, tsunamis have extremely long periods (the time for the next wave top to pass a point after the previous one), from minutes to hours, and long wavelengths of up to several hundred kilometres. This is very different from typical wind-generated swells on the ocean, which might have a period of about 10 seconds and a wavelength of 150 metres.

The height of a tsunami wave in open water is often less than one metre, and the height is spread over the wavelength of the tsunami which is multiple kilometres. This is unnoticeable to people on ships in deep water. Because it has such a large wavelength, the energy of a tsunami mobilizes the entire water column down to the sea bed. Typical ocean surface waves in deep water cause water motion to a depth equal to half their wavelength. This means, ocean surface wave motion will only reach down to a depth of a few 100 m or less. Tsunamis, by contrast, behave as 'shallow water waves' in the deep ocean.

Because a tsunami behaves like a 'shallow water wave,' its speed is based on the depth of the water. Typically, a tsunami wave will travel across a deep ocean at an average speed of 400 to 500 mph.([2]). As the wave approaches land, the sea shallows and the tsunami wave no longer travels as quickly, so it begins to 'pile-up'; the wave-front becomes steeper and taller, and there is less distance between crests. While a person at the surface of deep water would probably not even notice the tsunami, the wave can increase to a height of six stories or more as it approaches the coastline and compresses. The steepening process is analogous to the cracking of a tapered whip. As a wave goes down the whip from handle to tip, the same energy is deposited in less and less material, which then moves more violently as it receives this energy.

A wave becomes a 'shallow-water wave' when the ratio between the water depth and its wavelength gets very small, and since a tsunami has an extremely large wavelength (hundreds of kilometres), tsunamis act as a shallow-water wave even in deep oceanic water. Shallow-water waves move at a speed that is equal to the square root of the product of the acceleration of gravity (9.8 m/s2) and the water depth. For example, in the Pacific Ocean, where the typical water depth is about 4000 m, a tsunami travels at about 200 m/s (720 km/h or 450 mph) with little energy loss, even over long distances. At a water depth of 40 m, the speed would be 20 m/s (about 72 km/h or 45 mph), which is much slower than the speed in the open ocean but the wave would still be difficult to outrun.

Tsunamis propagate outward from their source, so coasts in the "shadow" of affected land masses are usually fairly safe. However, tsunami waves can diffract around land masses (as shown in this Indian Ocean tsunami animation as the waves reach southern Sri Lanka and India). It's also not necessary that they are symmetrical; tsunami waves may be much stronger in one direction than another, depending on the nature of the source and the surrounding geography.

Local geographic peculiarities can lead to seiche or standing waves forming, which can amplify the onshore damage. For instance, the tsunami that hit Hawaii on April 1, 1946 had a fifteen-minute interval between wave fronts. The natural resonant period of Hilo Bay is about thirty minutes. That meant that every second wave was in phase with the motion of Hilo Bay, creating a seiche in the bay. As a result, Hilo suffered worse damage than any other place in Hawaii, with the tsunami/seiche reaching a height of 14 m and killing 159 inhabitants.

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Answer 6

You Drown!

Thats got to be the biggest danger.

Answer 7

Are u serious? think HUGE wave of water ....what do u think?

Answer 8

U r kidding me/us, right?

Answer 9

you sorta dies. and houses get ripped apart.. etc

Answer 10

when it happen, people will die.