Because Geekery can be fun when you do it for a living
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"I checked my seismograph because all seismologists have a seismograph under their house and there's a lovely little local earthquake with an epicentre around about 20 kilometres away from where we live at Aranda," he said.
I think it's the notion of someone enjoying what they do for a living so much they want to continue with it when they get home. Then again, I suppose I do the same myself - when I'm working, I work tech support.