Category Archives: Pacific Ocean

Tsunami Awareness Week 2015

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March 22nd – 28th marks international Tsunami Awareness week. In the past decade humanity have witnessed to devastating tsunamis; Boxing day 2004 and Sendi March 11th 2011, both giving the world the bleak reminder of waters destructive power. But what actually is a tsunami and why are they so destructive?

Cars, trees and even buildings can be swept away as if they are mere toys. Japan March 11th 2011

tsunami

tsuːˈnɑːmi/
noun
noun: tsunami; plural noun: tsunami; plural noun: tsunamis
  1. a long, high sea wave caused by an earthquake or other disturbance.

The literal translation of ‘tsunami’ is ‘Harbour Wave’. This comes from the fact in open water a series of tsunami can travel thousands of mile visibly undetectable until they reach shallower waters causing them to rise up to the walls of water we know them to be.

They are caused by a large displacement of water most commonly by an earthquake or landslide, and are by far one of the most deadliest types of natural disaster. If you are in a coastal area and feel an earthquake it is often best to head to higher ground even if a tsunami alert has not been given, although most areas prone to tsunamis have quiet good warning systems waves still travel at speeds of up 500 km per hour, so even a few minutes warning may not always be sufficient.

The first warning of an income tsunami is often what is known as draw back. As water is displaced is often pulls water out to sea, so if you were sat on the beach it would appear as if the sea was withdrawing like at low tide but very quickly. Again if you see this, always best to get to high ground as quickly and calmly as possible.

A common misconception is that a tsunami is one wave, it is actually a series of waves. Also the first is often not the most powerful. This is why it can seem as the water just keeps coming as it gets further inland, its being forced by further waves.

Subduction zone earthquakes tend to cause the most powerful and deadly tsunamis such as the Boxing day or Sendi however the largest ever wave ever recorded was from a landslide induced tsunami at Lituya Bay, Alaska in 1958. Waves reached over 500 meters tall all this is in part the the shape of the bay as opposed to a landslide going in to open waters. Over 80% of tsunamis occur in the Pacific Ocean, the ring of fire.

If you are on a coast line in a at risk area, especially if holidaying and not too familiar with the area, make sure you check for evacuation routes and either easy access to high ground or strong, stable buildings which you can take shelter on high floors (wooden or unstable structures can be washed away!).

If you would like to know more here is a list of Tsunami Awareness Week links;

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Mg 6.9 Iwate and Tsunami warning

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At 8.06 am local time a magnitude 6.9 submarinal earthquake occurred of the coast of Iwate, Japan. JMA have claimed it is an after shock from the mg 9, March 11th megathrust quake in 2011.

The following tsunami alert was released although this was played up by some media stations to a full blown warning.

This Tsunami Warning/Advisory was issued in the past
Occurred at 08:06 JST 17 Feb 2015
Region name Sanriku Oki
Depth about 10 km
Magnitude 6.9
Click the map to zoom in

Tsunami Forecast Region Category of Tsunami Warning/Advisory
IWATE PREF. TSUNAMI ADVISORY

Tsunami Warnings / Tsunami Advisories

Issued at 08:09 JST 17 Feb 2015

******************Headline******************
Tsunami Advisories have been issued for the following coastal regions of Japan:
IWATE PREF.

*******************Text********************
Tsunami Advisories have been issued for the following coastal regions of Japan:
<Tsunami Advisory>
IWATE PREF.

***********About Tsunami Forecast************
<Tunami Advisory>
Marine threat is in place.
Get out of the water and leave the coast immediately.
As the strong current will continue, do not get in the sea or approach coasts until the advisory is cleared.

<Tsunami Forecast (Slight Sea Level Change)>
Though there may be slight sea-level change in coastal regions, no tsunami damage is expected.

******* Earthquake Information ********
Occurred at 08:06 JST 17 Feb 2015
Region name SANRIKU OKI
Latitude 39.9N
Longitude 144.5E
Depth about 10 km
Magnitude 6.9

The following arrival times were issued;

Tsunami Forecast Region/
Tsunami Observation Site
High Tide Time Estimated Initial
Tsunami Arrival Time
<Tsunami Advisory>
  IWATE PREF. ( Area where tsunami is
expected to arrive first )
08:30 JST 17 Feb
    Miyako 13:28 JST 17 Feb 08:40 JST 17 Feb
    Ofunato 13:36 JST 17 Feb 08:40 JST 17 Feb
    Kamaishi 13:36 JST 17 Feb 08:40 JST 17 Feb
    Kuji-ko 13:23 JST 17 Feb 08:50 JST 17 Feb

The warning was then terminated at 10.21 local time.