Because my article Japan today, Jerusalem tomorrow made such a large splash, I wanted to post the the most up-to-date, accurate and relevant data from the USGS:
National Geophysical Data Center
1 AD to 1000: 15 earthquakes 7.0 or higher (NGDC)
(One every 66 years)
1000 to 1800: 114 7.0 or higher (NGDC)
(One every 7 years)
1800 to 1900: 115 7.0 or higher (NGDC)
(One every 10 months)
(1935 Richter Scale invented)
1900 to 1980: 774 7.0 or higher (NGDC)
(One every 37 days)
United States Geological Survey
1980 to 2000: 255 earthquakes 7.0 or higher (USGS /NEIC)
(One every 28 days)
2000 to 2008: 127 earthquakes 7.0 or higher (USGS / NEIC)
(One every 26 days)
2009: 17 earthquakes 7.0 or higher (USGS / NEIC)
(One every 21 days)
2010: 20 earthquakes 7.0 or higher (USGS / NEIC)
(One every 18 days)
2011: 6 earthquakes 7.0 or higher in 3 months (USGS / NEIC)
(One every 15 days)