【摘要】 地震目录是地震监测预报、地震活动性等研究的重要资料.川滇地震科学实验场地区近几十年来积累了大量的地震记录,为实验场的地震科学研究提供了宝贵的数据.地震台网密度和仪器观测精度是逐步提高的,不同时期地震目录的完整性存在差异,因此进行现代仪器观测记录的地震目录最小完整性震级(M_C,Magnitude of Completeness)分析,对正确研究和认识该地区地震活动规律及其影响因素等具有重要意义.本文采用震级—序号方法、最大曲率法(MAXC,Maximum Curvature)和拟合度检测法(GFT,Goodness-of-Fit Test)分析了川滇地震科学实验场地区1970—2018年地震目录的最小完整性震级M_C值,得到了实验场地区及其内部各地震区(带)M_C值的时间演化特征和空间分布特征.结果表明,实验场地区及其内部各地震区(带)M_C值变化趋势大致为1970—1986年M_L2.0～2.6,1987—1999年M_L2.5～2.6,2000—2008年后M_L1.4～2.1,2009—2018年M_L1.2～1.9;实验场地区M_C值的空间分布大致呈现东北部和西南部较低、西北部和东南部较高的特征,其中云南最南端的澜沧—耿马区和思普区、四川西北部的理塘—木里区以及川藏交界处的金沙江带M_C值普遍较高,云南北部和四川南部的松潘—龙门山带、安宁河带、元谋区、楚雄—建水带和大理—丽江—盐源区M_C值普遍较低;强震会使M_C值出现突然升高、之后逐渐恢复的现象,其中M_C值升高程度与震级有一定相关性,并且强震导致的M_C值升高是M_C值空间和时间分布不均匀的原因之一.更多还原

【Abstract】 Earthquake catalogs are important data for earthquake monitoring and prediction, seismicity studies and other seismological studies. It is of great significance to analyze the minimum magnitude of completeness(M_C) for earthquake catalogs. China Seismic Experimental Site(CSES) has accumulated a large number of earthquakes in recent decades, which provides valuable data for the seismological studies in it. It is well known that the density of seismic networks and the accuracy of instrument is gradually increasing, so the minimum magnitude of completeness for the earthquake catalogs varies over time. Therefore, the analysis of the minimum magnitude of completeness for earthquake catalogs of the modern instrumental is of great significance for the current study and understanding of the law of seismicity and the influence factors in CSES. In this paper, the Magnitude-Sequence-Number method, the MAXC(Maximum Curvature) method, and the GFT(Goodness-of-Fit Test) method are used to analyze the minimum magnitude of completeness for the 1970—2018 earthquake catalog in CSES. The spatial distribution feature and the temporal variation feature of M_C in the whole CSES and each seismic zone within it are obtained. The results show that the change of M_C in CSES and the seismic zones within it is roughly M_L2.0～2.6 from 1970 to 1986, M_L2.5～2.6 from 1987 to 1999, M_L1.4～2.1 from 2000 to 2008 and M_L1.2～1.9 from 2009 to 2018. The spatial distribution feature of M_C in CSES is roughly lower in the northeast and southwest, and higher in the northwest and southeast. The M_C is generally higher in Lancang-Gengma zone at the southern end of Yunnan, Litang-Muli zone at the northwestern of Sichuan and Jinshajiang zone at the junction of Sichuan and Tibet. The M_C is generally lower in Songpan-Longmenshan zone, Anninghe zone, Yuanmou zone, Chuxiong-Jianshui zone and Dali-Lijiang-Yanyuan zone, which are in the northern Yunnan and southern Sichuan. A strong earthquake would cause that M_C suddenly increases and then gradually recovers. And the amount of the increasement of M_C has a certain correlation with the magnitude of the strong earthquake. The increasement of M_C caused by strong earthquakes is one of the reasons for the inhomogeneous spatial and temporal distribution of M_C.更多还原