RESEARCH ON THE METHODOLOGY AND PRINCIPLE OF SEISMIC ZONATIONRESULTS OF THE TRIALS IN NORTHERN CHINA

Based on the cognizance of the temporal-spatial inhomogeneity of seismicity in Northern China, adopting the results of earthquake prediction in the past two decades and the currently used methods of seismic hazard analysis, and after some seismic zonation trials in Northern China, some improvements on the zonation principle and methodology were made:(1) Seismic zones were taken as statistic units where seismicity parameters were obtained. Tendency analysis was introduced. Earthquake annual average occurrence rates were estimated corresponding to the seismicity level in the future period;(2) Average annual earthquake occurrence rates for a given magnitude interval of a specific seismic zone were assigned to potential sources in the same zone considering the relative risk levels among these sources. Thus, the risk of great earthquakes can be estimated.(3) The probabilistic spatial distribution function under the condition of magnitude interval was suggested to reflect the temporal and spatial inhomogeneity of seismicity.(4) An orientation function in the seismic hazard analysis model was adopted, which reflects the real conditions of earthquake foci in China.