THE PATTERN RECOGNITION OF SEISMICITY BEFORE MODERATE STRONG SHOCK IN NORTH CHINA

Based on the analysis of the historical earthquake documents in North China and the 12 different features selected for describing the seismic activity pattern in different perio-ds, taking occurrence period of earthquakes M≥7 or 6< M< 7 from 1525 to 1900, prem-onitory phenomena before 7 and 6 magnitude earthquake have been analysised with pattern recognition method at twice.The precursor information before M≥7 and 7 >M≥6 eart-hquake have been obtained.According these, the seismicity from 1951 to 1984 period have been recognized by same method.The results are consistent with practice.