| 中亚地震目录震级转换及其完整性分析 |
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| 引用本文： | 吴果,周庆,冉洪流.中亚地震目录震级转换及其完整性分析[J].震灾防御技术,2014,9(3):368-383. |
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| 作者姓名： | 吴果 周庆 冉洪流 |
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| 作者单位： | 中国地震局地质研究所,北京,100029 |
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| 基金项目： | 国家科技支撑计划课题“特大地震危险区识别及危险性评价方法研究（2010BAK15B01）”；地震行业科研专项“地震安全性评价分类、关键技术指标确定及国家标准修订研究（201408002）” |
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| 摘 要： | 为编制能够应用于地震危险性分析的中亚地区统一震级标度为矩震级的地震目录,从国际地震中心（ISC）下载得到该地区1907-2012年的地震数据,该数据包含众多机构不同震级标度的地震记录.以MW,GCMT为参考机构震级标度,并用最小二乘法拟合了其他机构震级标度与MW,GCMT之间的转换关系.在挑选某次地震事件的唯一震级记录时,以对应转换关系的相关系数大且剩余标准差小为准则进行筛选.对于少量没有震级转换关系或者拟合优度过差的地震记录,使用间接转换关系或者全球转换关系予以补充转换.震级转换后,用时空窗法删除前余震,并考虑构造环境和地震活动水平的空间差异性将研究区划分成5个子区域.采用地震记录时间累积曲线法、最大曲率法（MAXC）和拟合优度检验法（GFT）综合分析各个分区的最小完整震级（MC）,并在此基础上用极大似然法拟合相应的地震活动性参数.结果表明,每种完整性分析方法各具一定的优缺点,但采用综合分析的方法能够得出最佳的MC.地震记录时间累积曲线法能分析出高质量地震目录的起始时间,以作为后两种方法的基础,但容易受到地震活动水平随时间波动的影响.由于研究区目录质量较差,最大曲率法误差过大以至于只能作为其他方法的补充,拟合优度检验法的GFT参数也普遍只能达到80％左右.GFT最大值点可能并不对应MC,但是MC通常都在GFT极大值点取得.5个分区1964-2012年的MC普遍在Mw4.8左右,b值在1.136-1.514之间波动.
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| 关 键 词： | 矩震级 震级转换 最小完整震级 最大曲率法 拟合优度检验法 极大似然法 |
| 收稿时间： | 2014/2/15 0:00:00 |
Magnitude Conversion of Earthquake Catalog in Central Asia and the Completeness Analysis |
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| Wu Guo,Zhou Qing and Ran Hongliu.Magnitude Conversion of Earthquake Catalog in Central Asia and the Completeness Analysis[J].Technology for Earthquake Disaster Prevention,2014,9(3):368-383. |
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| Authors: | Wu Guo Zhou Qing and Ran Hongliu |
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| Institution: | Institute of Geology, China Earthquake Administration, Beijing 100029, China;Institute of Geology, China Earthquake Administration, Beijing 100029, China;Institute of Geology, China Earthquake Administration, Beijing 100029, China |
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| Abstract: | In order to compile a homogeneous catalog in moment magnitude for central Asia which can be used in seismic hazard analysis,we downloaded the seismic data during period 1907-2012 from the International Seismological Center （ISC）.The earthquake magnitudes of the data are reported in different scales and come from a variety of sources.In this study we take MW,GCMT as the reference magnitude,then derive a host of empirical relationships between magnitude scales from other institutions with MW,GCMT through least squares technique.The process,for choosing magnitude scale to a seismic event,follows a rule that giving priority to the one with larger correlation coefficient and smaller residual standard deviation in relevant regression relationship.Indirect conversion relationships and relationships derived from global seismic data serve as supplement when lack of direct conversion relations or the level of goodness of fit is too poor.A spatial and temporal windowing method is applied to remove pre-aftershocks,then the study area is divided into 5 smaller zones on the basis of spatial difference in structural setting and seismic activity.The identification of completeness magnitude （MC） for each zone is done by the combination of three kinds of methods：cumulative number of earthquakes plotted against time,maximum curvature （MAXC） and goodness of fit text （GFT）.The seismicity parameters of zones are calculated with maximum likelihood method on the basis of completeness analysis of catalog at last.Results indicate that though each method has its own advantage and drawbacks,we can acquire optimum MC when used in combination with other methods.Graph between time and cumulative number of earthquakes can be used to identify the starting time of high-quality catalog,which is the basis of the MAXC and GFT,but it could be easily affected by seismicity fluctuations over time.Because of poor data quality in the study region,the error of MAXC is so big that it can only be used as supplement for two other methods an |
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| Keywords: | Moment magnitude Magnitude scales transformation Completeness magnitude Maximum curvature Goodness of fit text Maximum likelihood |
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