The basics of earthquake forecasting Earthquake forecasting is a little like weather forecasting. It’s based on maths, knowledge of what’s happened in the past, and a dollop of human scientific judgment. Think of an earthquake forecast as a completed puzzle or jigsaw. Every puzzle is made up of small pieces. And there are all sorts of puzzle pieces that inform these forecasts. To give you an example, one piece is a concept called Omori’s Law – which helps define how the rate of aftershocks decays, or drops off, over time. This concept, along with, say, knowledge about a particular fault, could be used to build up a picture of how many aftershocks are expected after an earthquake.