# The frequency of large [[earthquakes]] (more than 6.99 on the Richter scale) doubles roughly every 40 years,<ref>http://www.earth.webecs.co.uk/</ref> rendering long-term stability impossible. Large earthquakes have increased by more than 20% in only the last decade.<ref>http://earthquake.usgs.gov/earthquakes/eqarchives/year/eqstats.php Meanwhile, there is a claim that the global risk of big earthquakes has not increased over the last hundred years [http://www.pnas.org/content/early/2011/12/12/1118525109.abstract Peter M. Shearer, Philip B. Stark: ''Global risk of big earthquakes has not recently increased''] [http://www.pnas.org PNAS], Dec 19, 2011, doi: 10.1073/pnas.1118525109</ref> | # The frequency of large [[earthquakes]] (more than 6.99 on the Richter scale) doubles roughly every 40 years,<ref>http://www.earth.webecs.co.uk/</ref> rendering long-term stability impossible. Large earthquakes have increased by more than 20% in only the last decade.<ref>http://earthquake.usgs.gov/earthquakes/eqarchives/year/eqstats.php Meanwhile, there is a claim that the global risk of big earthquakes has not increased over the last hundred years [http://www.pnas.org/content/early/2011/12/12/1118525109.abstract Peter M. Shearer, Philip B. Stark: ''Global risk of big earthquakes has not recently increased''] [http://www.pnas.org PNAS], Dec 19, 2011, doi: 10.1073/pnas.1118525109</ref> |