Seismologists work on understanding the movements of the earth and how they might affect the people and built structures on the surface. The information and knowledge that they have, though, is only of use if it helps inform the planning, preparation, and response to earthquakes. Perhaps the most important, but also the most difficult, questions that seismologists are asked are ‘what is the chance of a damaging earthquake happening in this area, and if it does, what are its likely effects?’ This is the basis for operational earthquake forecasting (OEF), and operational earthquake loss forecasting (OELF), and the answers are always going to have a lot of uncertainty: earthquakes cannot be predicted, however much we know and understand – but we can some-times tell that they are more likely in certain areas due to movements that have been detected in the earth’s crust.