2008 Market Rasen earthquake Caythorpe, all three in South Kesteven. The cost of insurance payouts was estimated to be around £30 million, with the majority of damage being done to chimneys, roof tiles and by falling masonry. The tremor was the largest earthquake to affect the UK since the 1984 Llŷn Peninsula earthquake, which measured 5.4 on the Richter scale. The British Geological Survey gave the earthquake a reading of 5.2M, while the United States Geological Survey reported it measured 4.8M. The French Atomic Energy Commission estimated the magnitude was 5.4M. A total of nine aftershocks were recorded. The largest, measuring 2.8 on the
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.