Characteristics of Seismicity and Sequence Patterns in Qilianshan Seismic Belt
LIU Xiao-feng,XIAO Li-zhu,MEI Xiu-ping,XU Huei (Lanzhou Institute of Seismology,CEA,Lanzhou 730000,China)
The moderate-strong earthquakes in Qilianshan seismic belt shows the character of becoming groups. The seismicity patterns before the main shock are seismic gaps,precursor earthquakes, and enhanced regional seismicity, et al.. The seismic gaps mostly are mid-term abnormity. The signs from mid-term to short-term are those precursor earthquakes occur at the edge of or in the gaps, the gaps cease for 1~3 months,or the gaps dissemble with the small earthquake occurrs in it. The precursor earthquakes generally occur 1~6 months before the main shock and the distances between the precursor earthquake and main shock are less than 30 km, with the ΔM=1.5~3.0. Furthemore, the earthquake sequence patterns, the b,h values of the aftershock sequences are statisticsed and analysed. All above reseach will serve in seismic trend prediction after strong earthquake.