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.
New Madrid Seismic Zone
The first known written record of an earthquake felt in the NMSZ was from a French missionary traveling up the Mississippi with a party of explorers. At 1 pm on Christmas Day 1699, at a site near the present-day location of Memphis, the party was startled by a short period of ground shaking.Hundreds of aftershocks of the 1811–1812 series followed over a period of several years. Aftershocks strong enough to be felt occurred until 1817. The largest earthquakes to have occurred since then were on January 4, 1843, and October 31, 1895, with magnitude estimates of 6.0 and 6.6, respectively. The 1895 had its epicenter near Charleston, Missouri. The quake damaged virtually all the buildings in Charleston, created sand volcanoes by the city, cracked a pier on the Cairo Rail Bridge and toppled chimneys in St. Louis, Missouri; Memphis, Tennessee; Gadsden, Alabama; and Evansville, Indiana.