Tsunamis are quite interesting, as they only happen after a large displacement of water.

Usually, the waves travel quite weirdly. Sometimes there are waves which bounce off of land and go back to sea. Sometimes they go straight to land and don't bother any other pieces of land around them.

So why does this happen?

Why do some tsunamis go straight to land while others are spread out?

And why others take various pathways toward land or the open sea?

  • 2
    $\begingroup$ I am a bit confused by the question, and think it might be to general for a meaningful answer. Are you asking for the cause of the variability in tsunami pathways? $\endgroup$
    – Neo
    Apr 15, 2014 at 23:41
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    $\begingroup$ @Neo Pretty much. I'll edit the question in a minute, but basically I'm wondering why some tsunamis go straight to land, while some spread out, and others have wave "bounce back". $\endgroup$
    – hichris123
    Apr 15, 2014 at 23:45
  • $\begingroup$ Do you have an example of tsunami reflection? $\endgroup$
    – winwaed
    Apr 16, 2014 at 1:08
  • $\begingroup$ @winwaed Just a quick Google search turned up this, which includes an example of waves reflecting off of an ocean ridge. $\endgroup$
    – hichris123
    Apr 16, 2014 at 1:10
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    $\begingroup$ Hichris, thanks - I think that URL also answers your question. $\endgroup$
    – winwaed
    Apr 16, 2014 at 1:12

1 Answer 1


The answer to some parts of your question lie mainly in basic physics, there are a number of factors that will affect how a Tsunami will travel after the initial water displacement.

For example, is the initial displacement a point event (such as Tsunami caused by landslides), or an event occurring along a long line, such as the massive fault movement that caused the "Boxing Day" Tsunami of 2004.

A point event allows the water to spread out in all directions from that point, similar to ripples in a pond after a raindrop or pebble falls in, the energy is dissipated equally in all directions and therefore the water displacement - and thus the height of the breaking Tsunami wave - decreases rapidly.

Conversely, a linear event such as the "Boxing Day" tsunami doesn't allow the energy to dissipate equally in all directions, because at any given point along the wave-front, there is more "wave" to the 'left' and 'right' that prevent that dissipation. This allows the energy to be transferred over much greater distances, and allowing the water displacement to be preserved.

As for why some land gets passed by, this is usually an effect of the local topography, going back to the Boxing Day Tsunami example, the Maldives were less effected than they could have been because there was no continental shelf for the waves to encounter and build up on. Bangladesh and other countries north of the fault-line also suffered less than they could have done because the northern and southern ends of the fault acted like point-events, and the waves to the north and south dissipated much more rapidly than those to the east and west.


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