There have been a couple of other minor shake events since this took place, but this video is correct: this is unexplained. It is a real video, posted by someone who watches these seismographs.
http://www.youtube.com/watch?v=j1Ktbub_IYk&feature=player_embeddedStory Source:
http://www.youtube.com/watch?v=j1Ktbub_IYk&feature=player_embedded Dreamland Video podcast
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