汾渭地震带区域地震目录最小完整震级分析
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摘要
利用基于G-R关系基础之上的MBS法和GFT法,对比分析了1970年以来汾渭地震带台站建设各阶段ML≥1.0的地震目录的完整性。结果表明:在基础地震台站建设阶段(1970—1977年),ML2.4—ML2.5级以上地震基本完整;在地震台站调整以及遥测台站建设阶段(1978—1997年),最小完整震级为ML2.2;在地震台站数字化阶段(1998年—至今),ML2.0—ML2.1级以上地震目录基本完整。从时间尺度上看,随着时间的推移,汾渭地震带相同起始震级所对应的拟合优度值基本呈稳定增加趋势,表明汾渭地震带的地震监测能力在逐步提高。文中采用改进的b值标准差法对b值基本稳定时所对应的震级进行了识别和评价,提高了最小完整震级识别的准确性,同时还分析了汾渭地震带最小完整震级的空间分布情况。结果表明,汾渭地震带北部Mc较中南部偏低。研究结果为汾渭地震带地震活动性研究、地震台网优化布置提供了基本依据。
Two methods (MBS and GFT methods ) based on G-R relationship have been used to analyze the integrality of the earthquake catalog of ML≥1.0 in three stages of the sesimic station network in Fenwei seismic region since 1970 in this paper. The results show that during base station construction phase from 1970 to 1977, the earthquake of the magnitude over 2.5 is integrated. In station adjustment and telemetry stations construction phase from 1978 to 1997, the minimum magnitude of integrated earthquakes is 2.2. In station digital phase from 1998 until now, the minimum magnitude of integrated earthquakes is from 2.0 to 2.1. The above observation suggests that as time goes on, the goodness of fit corresponding to the same initial magnitude is increasing steadily, which indicates that the earthquake monitoring capability of Fenwei seismic region is improving gradually with time. In this article, we use the improved standard deviation of the b values when they are relatively stable to estimate the magnitude, resulting in the relatively high accuracy of evaluation the minimum complete magnitude. At the same time we have also analyzed the spatial distribution of the minimum complete magnitude. our results show that Mc in the north of Fenwei seismic region is lower than in the south. The methods we proposed in this paper is helpful to provide fundamental basis for seismic analysis and station network optimization arrangement of Fenwei seismic region.
引文
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