In a general sense, 'overdue' means that an event was to have occurred by now, and has not yet; this requires a due date for the event. And of course a precise prediction for an earthquake date in the past that didn't happen is pretty stuffed with it.
People who choose this path are often extremely driven and deeply in touch with their faith. Example: The Christian rock band Barlow Girl is famous for embracing the “no dating” approach. And when you like somebody, it’s nice to be able to express that feeling with physical affection.
Tom Jordan of USC and the Southern California Earthquake Center caused a bit of a stir by claiming that the southern San Andreas fault was 'locked, loaded and ready to roll'.
This was interpreted by many as meaning that an earthquake on the fault is 'overdue', although it's not clear what 'overdue' means in this scientific context.
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