Why did an earthquake occur in Illinois?
The earthquake of April 18th along the Illinois/Indiana border is not the first to occur in this region. Several similar sized and smaller earthquakes have occurred in the area over the last 100 years. Scientists have identified these earthquakes as occurring on the Wabash fault zone, the Wabash fault zone lies along what is called a failed rift. Failed rifts are portions of the continent that were stretched at some point in the past, causing the crust to break (fault). Now that the continent is no longer stretching and is in fact under compression, these faults are being reactivated. Basically, the continent is like a log raft that has been assembled over billions of years, some of the lashings between the logs are loose and when the continent (or raft) gets pushed, the places where it is loose move. Why was it felt over such a wide area? While an earthquake of this magnitude in California would generally only be felt on a smaller, several county scale, the smooth, relatively unbroken
