Characteristics of seismic activity before Chile M_W8.8 earthquake in 2010

The tempo-spatial variation of seismic activity before great Chile M_W8.8 earthquake on February 27, 2010 is studied. Some results are as follows: ① Two types of seismic gaps appeared before the Chile M_W8.8 shock. One is background gap of M_W≥8.0 earthquakes with 360 km length since 1900, the other is seismogenic gap formed by M≥5.5 earthquakes with 780 km length five years before the Chile earthquake; ② There was only one M_W7.1 earthquake in the middle and southern part of Chile from 1986 to 2010. The obvious quiescence of M_W≥7.0 earthquake is the long-term background anomaly for the Chile earthquake; ③ The quiescence of M≥6.5 earthquakes appeared in South American block and its vicinity during the period from 2007 to 2009, and the quietude state has been disappeared three months before the Chile M_W8.8 earthquake; ④ The deep and intermediate-depth earthquake activity has been noticeablely strengthened in the subduction zone of South American block since 1993; ⑤ The great Chile earthquake shows that global seismicity is still in the active period of M_W≥8.5 earthquakes since 2004. Based on the characteristics of the former two active periods, several great earthquakes with M_W≥8.5 would take place in a few years. In addition, the circum-Pacific seismic belt would be the main region for M_W≥8.0 earthquakes.