In a recent development an Earthquake Aftershock of the magnitude of 4.5 richter has struck again. According to United States Geological Survey, this quake struck at 10:14 a.m. local time 6.2 miles (10 kilometers) below the surface. In terms of distance, it was 13 km (8 miles) E (81°) from West Salem, IL: 14 km (8 miles) W (275°) from Allendale, IL: 15 km (10 miles) NE (48°) from Bone Gap, IL: 68 km (42 miles) NNW (336°) from Evansville, IN; 207 km (129 miles) E (92°) from St. Louis, MO.

Earlier, an earthquake occurred 35 km (20 miles) SW of Vincennes, Indiana and 205 km (125 miles) SW of INDIANAPOLIS, Indiana at 3:36 AM MDT, Apr 18, 2008 (4:36 AM CDT in Illinois).Reports of minor structural damage in West Salem, Illinois and Louisville, Kentucky. Felt over a wide area of the central United States with felt reports as far west as Kansas, as far north as the Upper Peninsula of Michigan and as far south as Georgia.

The Illinois basin - Ozark dome region covers parts of Indiana, Kentucky, Illinois, Missouri, and Arkansas and stretches from Indianapolis and St. Louis to Memphis. Moderately frequent earthquakes occur at irregular intervals throughout the region. The largest historical earthquake in the region (magnitude 5.4) damaged southern Illinois in 1968. Moderately damaging earthquakes strike somewhere in the region each decade or two, and smaller earthquakes are felt about once or twice a year. In addition, geologists have found evidence of eight or more prehistoric earthquakes over the last 25,000 years that were much larger than any observed historically in the region.