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Earth Google Japan Science

Using Googlemaps To Simulate Tsunamis 40

Posted by timothy from the you're-all-wet dept.
flemster writes "Tsunami mapper is a new site which uses the googlemaps elevation service and the flood fill algorithm to predict which areas near a coast are likely to be affected by a tsunami. You can search for your local beach, set a wave heading and height and then double click the tsunami starting point off the coast, after which the tsunami range will be drawn. Naturally, predicting a tsunami is far more complicated than this and this application is a general guide and not a true predictor. However the simulations of the recent Japanese simulation are interesting. Compare the tsunami mapper simulation with this aerial photo of Ishinomaki after the March tsunami."
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Using Googlemaps To Simulate Tsunamis More

Using Googlemaps To Simulate Tsunamis

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  • Didn't work... (Score:4, Insightful)

    by SIGBUS ( 8236 ) on Saturday April 30, 2011 @03:50PM (#35986266) Homepage

    "Elevation of starting location is 158.171 meters. A tsunami must start in the ocean."

    Then again, I was trying to create a tsunami on Lake Michigan.

    • I couldn't get it to work in the ocean, either. I always got told that my tsunami didn't reach land.

    • Re: (Score:3, Informative)

      by Ol Biscuitbarrel ( 1859702 )

      I also like "It's best to start the tsunami a few kilometers from the shore." This in reference to the tsunami not reaching Aberdeen Washington, no matter where I start them from. Maybe the coders are into Nirvana?

      Would help to add a scale so we can figure how much map covers those few kms, too...

      OK, after looking at the Gallery I think they meant meters, not kilometers - you doubleclick right offshore to mark where, uh, the news crews will congregate? Wave fronts are a bit more diffuse than that, I beli

      • OK, after looking at the Gallery I think they meant meters, not kilometers - you doubleclick right offshore to mark where, uh, the news crews will congregate? Wave fronts are a bit more diffuse than that, I believe.

        Thanks for the hint. I now can create tsunamis as well. And I learned that even kilometer high tsunamis won't go very far. ;-)

      • Here's how it works. Pick a point of 0 elevation. Check the surrounding ten by ten km square (adjusting for "wave direction"). For each 1km by 1 km square in the area, if the elevation is less than the wave height, paint it blue.

        • Here's how it works. Pick a point of 0 elevation. Check the surrounding ten by ten km square (adjusting for "wave direction"). For each 1km by 1 km square in the area, if the elevation is less than the wave height, paint it blue.

          In other words, this so-called "simulation" is absolutely worthless.

    • Re: (Score:2)

      by mpe ( 36238 )
      "Elevation of starting location is 158.171 meters. A tsunami must start in the ocean."
      Then again, I was trying to create a tsunami on Lake Michigan.

      Maybe the model they are using dosn't allow for impact generated tsunamis. Is water density also a factor. I suspect the water depth is more relevent than its elevation too.

  • Oh my god, when you select "West" it draws a blue square to the west of where you clicked, and when you select "East" it draws a blue square to the east. That's incredible. This must have taken five PhDs 2 months to make.

  • I didn't try it, but could someone who did confirm that it knows jack squat about energy?

    A "5-meter" tsunami is going to go halfway up a 500-meter cliff if it retains enough energy.

    • I didn't try it, but could someone who did confirm that it knows jack squat about energy?

      It doesn't. As the summary says, it's a flood-fill algorithm - it works like the paint bucket in an image editor, where the flood-stop condition is "elevation >= wave height". Oh, and it only checks a few kilometers worth of land at a time.

      A "5-meter" tsunami is going to go halfway up a 500-meter cliff if it retains enough energy.

      No, because tsunami (like any wave) is a wave, not flow. A 5-meter tsunami is 5 meters

      • Re: (Score:2)

        by blair1q ( 305137 )

        No, a tsunami is a longitudinal body wave in the horizontal displacement of the medium. An ordinary wave is a transverse surface wave in the height of the medium.

        The height of an ordinary wave is most of the energy involved, no matter how deep the water. You cause them by blowing on the surface of your bathtub.

        The height of a tsunami is only a tiny indication of the total energy involved; it's not even proportional when the depth is accounted for. It's like moving your entire bathtub back and forth.

        A tsu

  • My country is doomed!

    It doesn't want to start a wave if the elevation is above 2 meters. Well, about 60% of my country, The Netherlands, is below that magic number.
    Everywhere I click that's below 2 meters just generates a 10x10 km blue square, so I suppose that's flooded. I took a 20meter tsunami and traced the 2 meter line in my country, having the tsunami travel south-east mostly. Then the blue squares are not entirely filled in, the "water" only flows until it hits things above 20 meters.
    So basically wha

    • Don't worry (Score:1)

      by Anonymous Coward

      The Doggerland tsunami hypothesis is at present just that, a hypothesis. IANAA (nor a P or a G) but as I understand it there are problems with the hypothesis that are still to be resolved. Even so, if tsunami in the North sea come by every 10.000 years or so and the last one was about 8000 years ago, then that might be too close for comfort. So, how are we doing?
      Even though self-proclaimed paragnosts and spirituals predict that the Netherlands will be hit by a tsunami every other year, so far the North Sea

    • AFAIK Doggerland was mostly just submerged by rising sea levels at the start of the current interglacial period; the remaining bits of it may have been washed away by a tsunami, but most of it was already underwater. I'm not arguing with your contention that a North Sea tsunami would be devastating, just pointing out that describing Doggerland as "an area about the size of Ireland or Colorado that was washed away in the last known tsunami" is a bit of an exaggeration.

  • Using Googlemaps To Stimulate Tsunamis

    Phew! ...

  • Thanks for the feedback. A couple of points:
    1) Yes - you do need to set the direction before clicking on the map. Otherwise the wave will go in the wrong direction and the results will be bad.
    Next release (give me 24 hours) will force the user to enter a direction and also put a little arrow showing the direction chosen.

    2) Yes - the flooded area can only be 10km by 10km. I chose this based on some basic research on tsunami reach and needing a reasonable response time from google's elevation service.

    • Perhaps you could've slightly improved your piece of 'code' before slashing it here, but then anything get plastered around here these days...

      Google maps DEM (Digital Elevation Model) is based on SRTM [nasa.gov] (Shuttle Radar Topography Mission) data over most of the globe. You can download [usgs.gov] the original processed data from NASA and apply it to any GIS software [opensourcegis.org] of your choice.

      Then with a single click of the elevation tool you can raise or lower the global sea level by x meters of your choice. Was playing around wi

    • Re: (Score:1)

      by Askmum ( 1038780 )

      3) Yes - it only uses flood fill algorithm to determine if an error is blue or not. If the elevation of the location is less than the wave and it has a neighboring sector which is blue, then its blue. If someone can point me to the maths that describes how to calculate this based on the wave's energy, velocity etc then I'll have a try. But there may be a limit to what can be done in 300 lines of JavaScript :-)

      Then I have a far easier solution. Find and show an overlay with 1 meter increments and you know

  • lame simulation.
  • Thanks everyone for their feedback. Nothing like getting slash-dotted for finding out what the world thinks.

    Now that its off the front page, I'm going to to take the opportunity to get the last word.

    Few more points:
    1) In the initial description it does say "... this application is a general guide and not a true prediction" and so yes I agree flood fill isn't the most accurate algorithm for predicting tsunamis. More accurate is GeoClaw [washington.edu] which has a lot of fortran and phython code and some very detailed

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