Randolph, Tennessee in the area since 1974 occurred on August 19, 1994 – the temblor was measured 3.2 on the Richter scale with an epicenter at coordinates , ca. west of Randolph, at a depth of . On January 16, 2009 at 3:09 p.m. local time (21:09 UTC), "a small earthquake shook portions of Tipton County". The earthquake was measured at a magnitude 2.8 on the Richter scale. According to the Center for Earthquake Research and Information (CERI), the epicenter of the temblor was reported to be at coordinates at a depth of . There were no reports of damage caused by
Moment magnitude scale band. To simplify this calculation, he noted that the lowest frequency parts of the spectrum can often be used to estimate the rest of the spectrum. The lowest frequency asymptote of a seismic spectrum is characterized by the seismic moment, . Using an approximate relation between radiated energy and seismic moment (which assumes stress drop is complete and ignores fracture energy), (where E is in Joules and is in Nformula_4m), Kanamori approximated by The formula above made it much easier to estimate the energy-based magnitude , but it changed the fundamental nature of the scale into a moment magnitude scale.