• Question: How Does an Earthquake Trigger Tsunamis Thousands of Kilometers Away?

    Asked by epicurustacoboy to Jamie, Jodie, Kat, Mark, Niamh on 15 Mar 2011 in Categories: .
    • Photo: Mark Hill

      Mark Hill answered on 14 Mar 2011:

      Hi,
      Where are you getting all these good questions from?

      Not being a seismologist, or geologist, perhaps Jamie could help more. However, I think that the tsunami is caused at the point of the earthquake epicentre, by a sudden change in the level of the ocean floor. That causes the start of the wave, deep underwater. What we see as the tsunami is in fact the wave as it reaches shallower water, and then becomes visible (in Japan, VERY visible).

      Jamie, can you help?

      Mark.

    • Photo: Jodie Dunnett

      Jodie Dunnett answered on 14 Mar 2011:

      As far as I know, an earthquake may cause a large amount of water to be displaced and this then becomes a tsunami. The energy in the wave is such that it will continue until it hits something which in some cases may mean it has travelled for thousands of miles. Sorry, I’m sure someone else will be able to provide a better answer than this 🙂

    • Photo: Jamie Pringle

      Jamie Pringle answered on 14 Mar 2011:

      Hello there,
      Yes my colleagues are both correct; it is the physical movement of the ocean floor that has moved that displaced the water that forms the tsunami. This displacement moves radially in all directions from the focus (the centre point) of the earthquake; it was just unlucky for Japan’s coastal regions that they were so close that the early warning systems did not give the local population time to escape. This was not the case with Hawaii and more distant populations which did have time to hear the warning and move inland/higher ground.

      The other problem with this earthquake was that it was so shallow (geologically speaking) – only 15km down. This made it far worse than if the earthquake focus was deeper down in the crust. Also – as the tsunami wave gets towards the coast and the ocean floor shallows, the wave increases in height and causes even more damage (10m+ being recorded). Very sad for the population there.

      See this link for more information: http://www.bgs.ac.uk/research/highlights/earthquakes/honshuMarch2011.html

    • Photo: Niamh Nic Daeid

      Niamh Nic Daeid answered on 15 Mar 2011:

      Hi Epicurustacoboy – I think Jamie has given you the answer to this one much better than I could 🙂

Comments