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
Richter magnitude scale used by astronomers. Second, he wanted a magnitude of zero to be around the limit of human perceptibility. Third, he specified the Wood-Anderson seismograph as the standard instrument for producing seismograms. Magnitude was then defined as "the logarithm of the maximum trace amplitude, expressed in microns", measured at a distance of 100 km. The scale was calibrated by defining a magnitude 3 shock as one that produces (at a distance of 100 km) a maximum amplitude of 1 micron (1 µm, or 0.001 millimeters) on a seismogram recorded by a Wood-Anderson torsion seismograph. Finally, Richter calculated a table of distance