As Morocco is hit by its deadliest earthquake in decades, killing at least 820 people, Professor of Planetary Geosciences at the Open University, David Rothery, explains that "there's been nothing bigger than 6.0 within 500 kilometers of this since at least 1900," making this disaster a "one in a century" occurrence. He adds that Earth's movements due to the collision between Africa and Europe are still continuing and more is expected. Morocco "will have to think very seriously if it is worth investing in earthquake-resilient building", he says, but it's "a very difficult decision to make" considering the next one could only happen in a century. SOUNDBITES