Abstract: We study seismic distribution before the 17 large earthquakes in Xinijang and its surrounding, Sichuan-Yunnan and Qinghai regions, by scanning in a large range and long-time scale with the uniform seismic catalogue and Mapsis software, and draw elliptic gaps. The results show that except three earthquakes in the early 1970s, most large earthquakes exit good seismic gaps, including the Wenchuan M_S8.0 earthquake on May, 2008 and Yushu M_S7.1 earthquake on April, 2010. The magnitude of large earthquakes and gap length have positive correlations, but the magnitude of large earthquakes and the gap starting and forming time scale have no obvious correlation. The definite condition of ellipse is not strict, so it is easy to be multi-dimensional in drawing gaps in complicated situation, and gap confidence may decrease and false forecast may increase.

Key words: Large earthquakes in Xinjiang and its surrounding, Sichuan-Yunnan-Qinghai region, Elliptic gaps, Retrospective Research