Induced seismicity in Basel
The largest event prompted concern from local residents. The six borehole seismometers installed near the Basel injection well to monitor the natural background seismicity and the geothermal stimulation recorded more than 13,500 potential events connected with the geothermal project, from which 3,124 were of sufficient quality to permit [hypocenter] determinations in the period 2–12 December 2006, which spanned the main stimulation and the decline in the event rate. During the post-stimulation period from 13 December 2006 onward, a further 350 locatable events were detected up to 2 May 2007, by which time events were occurring sporadically at around one per day. In all, locations for more than 3,500 events were determined.
1968 Illinois earthquake
The 1968 Illinois earthquake (a "New Madrid event") was the largest recorded earthquake in the U.S. Midwestern state of Illinois. Striking at 11:02 a.m. on November 9, it measured 5.4 on the Richter scale. Although there were no fatalities, the event caused considerable structural damage to buildings, including the toppling of chimneys and shaking in Chicago, the region's largest city. The earthquake was one of the most widely felt in U.S. history, affecting 23 states over an area of . In studying its cause, scientists discovered the Cottage Grove Fault in the Southern Illinois Basin.