Characteristics of seismic activity before27 February2010 Chile MW8.8 earthquake

Spatio-temporal variation of seismic activity before the greatChileearthquake on February 27, 2010, is studied. Some results are as follows: ① Two types of seismic gaps appeared before the Chile MW8.8 shock. One is the background gap of MWge;8.0 earthquakes with360 kmlong since 1900. The other is the seismogenic gap of Mge;5.5 earthquakes with780 kmlong 5 years before the Chile earthquake. ② There was only one earthquake with MW7.1 inmiddle and southern part of Chile from 1986 to 2010. This is the long-term background anomaly of the obvious quiescence of MWge;7.0 earthquakes before the Chile earthquake. ③ The quiescence of earthquakes with Mge;6.5 appeared in South American Plate and its vicinity during 2007mdash;2009, and the quietude state has been disappeared three months before the MW8.8 shock. ④The deep and intermediate-depth earthquake activity has been noticeably strengthened in the subduction zone of South American Plate since 1993. ⑤ The great Chile earthquake shows that the global seismicity is still in the active period of MWge;8.5 earthquakes since 2004. Based on the characteristics of the former two active periods, several MWge;8.5 great earthquakes would take place in a few years. In addition, the circumPacific seismic belt would be the main region for MWge;8.0 earthquakes.