If cutoff level is 8 than:
1970/07/31 17:08 −1.49 −72.56 8.0 Colombia
1971/01/10 07:17 −3.132 139.697 8.1 Papua, Indonesia
1974/10/03 14:21 −12.254 −77.524 8.1 78 near the coast of central Peru
1976/08/16 16:11 6.292 124.090 8.0 8000 Mindanao, Philippines
1977/06/22 12:08 −22.878 −175.900 8.1 Tonga region
1977/08/19 06:08 −11.085 118.464 8.3 100 south of Sumbawa, Indonesia
1979/12/12 07:59 1.598 −79.358 8.1 600 near the coast of Ecuador
1985/03/03 22:47 −33.135 −71.871 8.0 177 offshore Valparaiso, Chile
1985/09/19 13:17 18.190 −102.533 8.0 9500 Michoacan, Mexico
1986/05/07 22:47 51.520 −174.776 8.0 Andreanof Islands, Aleutian Islands, Alaska
1989/05/23 10:54 −52.341 160.568 8.1 Macquarie Island region
http://earthquake.usgs.gov/earthquakes/eqarchives/year/mag8/magnitude8_1900_date.php
So the gap seems to be artificial, but more research needed.
If cutoff level is 8 than:
1970/07/31 17:08 −1.49 −72.56 8.0 Colombia
1971/01/10 07:17 −3.132 139.697 8.1 Papua, Indonesia
1974/10/03 14:21 −12.254 −77.524 8.1 78 near the coast of central Peru
1976/08/16 16:11 6.292 124.090 8.0 8000 Mindanao, Philippines
1977/06/22 12:08 −22.878 −175.900 8.1 Tonga region
1977/08/19 06:08 −11.085 118.464 8.3 100 south of Sumbawa, Indonesia
1979/12/12 07:59 1.598 −79.358 8.1 600 near the coast of Ecuador
1985/03/03 22:47 −33.135 −71.871 8.0 177 offshore Valparaiso, Chile
1985/09/19 13:17 18.190 −102.533 8.0 9500 Michoacan, Mexico
1986/05/07 22:47 51.520 −174.776 8.0 Andreanof Islands, Aleutian Islands, Alaska
1989/05/23 10:54 −52.341 160.568 8.1 Macquarie Island region
http://earthquake.usgs.gov/earthquakes/eqarchives/year/mag8/magnitude8_1900_date.php
So the gap seems to be artificial, but more research needed.