aftershock

Small earthquakes in unexpected locations are often a cause for concern. The worry is that these rumbles are harbingers of bigger quakes to come. But not always - a new study suggests that many of these tremors aren't warnings, but aftershocks. In particular, those that happen in the middle of continents, far away from the major fault-lines that separate tectonic plates, probably reflect past quakes rather than future ones. Earthquakes are a common occurrence on the boundaries between tectonic plates, and they occur at predictable spots. But they can often strike areas that are far away from…