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
Seismic magnitude scales times. As originally defined by m was based on the maximum amplitude of waves in the first 10 seconds or more. However, the length of the period influences the magnitude obtained. Early USGS/NEIC practice was to measure on the first second (just the first few P-waves), but since 1978 they measure the first twenty seconds. The modern practice is to measure short-period scale at less than three seconds, while the broadband scale is measured at periods of up to 30 seconds. The regional mb scale – also denoted mb_Lg, mbLg, MLg (USGS), Mn, and m – was developed by for