中短期地震前兆的模糊综合识别

FUZZY SYNTHETIC RECOGNITION OF MEDIUM-SHORT-TERM EARTHQUAKE PRECURSORS

本文把模糊模式识别的直接方法用于综合分析多台多种手段观测到的地震前兆资料,以便提取较大地震前几个月内可能出现的中短期前兆异常信息。 所用方法的基本技巧是,对每一个台的每一种前兆观测手段建立起适当的前兆从属函数,并进而确定出多手段或多台的综合前兆从属函数。首先以综合前兆从属函数为基础,识别出某一地区较大地震前出现的中短期前兆异常,然后将其归纳成可用于地震预报的中短期前兆模式。 借助于所提出的方法,本文着重分析处理了1979—1986年间日本东海地区及其邻近地区3个倾斜台、2个验潮站、2个水氡观测站、2个水位观测点和30个体积应变观测点的大量前兆观测资料,识别出了这一期间在该地区内发生的10余次6级以上地震前的中短期前兆异常时间,并得出了两类地震前兆模式:第一类前兆模式适用于在该地区内进行多种前兆手段的综合分析预报;第二类前兆模式适用于单种前兆手段(体积应变)的多台综合分析预报。 为对比起见,文中同时给出了我国唐山7.8级地震及其6.9级强余震前多台水氡含量变化的中短期前兆综合分析识别结果,所得出的前兆模式与日本东海地区的第二类前兆模式相符。

The direct method of fuzzy pattern recognition has been applied to the synthetic recognition of medium-short-term (several months) earthquake precursors of different kinds observed at different stations.The basic technique of this method is to construct a suitable membership function for each single precursor at each single station and then the comprehensive membership function for several precursors of different kinds or for the same precursor observed at different stations.By using this method,the precursors observed in the Tokai area and its vicinity of Japan are studied with emphasis. They are the radon content in ground water,groundwater level,tilt,tide and volume strain. The abundant observational data from 3 tilt stations,2 tide stations,2 stations for observation of radon content in ground water,2 stations for observation of water level and 30 stations for observation of volume strain are used. Two possible precursor patterns for medium-short-term earthquake prediction in the Tokai area were proposed. One is applied to the synthetic analysis of several precursors of different kinds and at different stations,the other is applied to the synthetic analysis of one-kind of precursor (volume strain) observed at different stations.For comparison,the result of synthetic recognition of medium-short-term precursors of radon content in ground water at many stations before the great M = 7.8 Tangshan earthquake of 1976 and its M = 6.9 strong aftershock observed in the Beijing-Tianjin-Tangshan area and its vicinity of China is introduced. The precursor pattern obtained corresponds to the second precursor pattern for the Tokai area of Japan.