• Question: Why land honsju get moved 2.5 metres after this earthquake in japan

    Asked by buuren to David, Luna, Mark, Melanie, Probash on 18 Mar 2011 in Categories: .
    • Photo: Melanie Stefan

      Melanie Stefan answered on 18 Mar 2011:

      That’s a question for David, I think!

    • Photo: Luna Munoz

      Luna Munoz answered on 18 Mar 2011:

      Sorry. I can take a guess but I’m sure others would know better than I – David?

    • Photo: David Pyle

      David Pyle answered on 18 Mar 2011:

      The network of global positioning system (GPS) instruments on Japan show that parts affected by the earthquake moved to the East (towards the Pacific); and some areas have also dropped in elevation. This can be explained by the release of ‘strain’ as the plates unlock during the earthquake. Over the many years before the quake, the two plates are locked together (with no slip on the plate boundary), but some movement between the plates will be taken up by squeezing the upper plate (Japan) upwards. When the locked part of the boundary is released (during a very large earthquake), the upper plate will spring back into position, moving down, and East. The process is an example of what is called ‘elastic rebound’.

      There’s a good videoclip of a cartoon of this on youtube.

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