| 全球地震活动性的定量研究(一)——全球浅源和深源地震活动性随时间的变化 |
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| 引用本文： | 吴佳翼,曹学锋.全球地震活动性的定量研究(一)——全球浅源和深源地震活动性随时间的变化[J].地震学报,1987,9(1):1-14. |
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| 作者姓名： | 吴佳翼 曹学锋 |
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| 作者单位： | 国家地震局地球物理研究所 |
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| 摘 要： | 本文利用地震活动性指数 A(b)对本世纪初以来的全球地震活动性作定量的研究,着重探讨全球地震活动随时间的变化.根据求 A(b)指数的结果,对阿部胜征和巴特、杜达的两种不同的世界地震目录作了对比分析.本世纪的全球地震活动总趋势是一种有起伏的衰减.全球深震和浅震活动水平分别在1950-1952年和1952-1955年有一个显着的下降,使得后半世纪的浅震活动水平普遍降低了0.3左右,浅震和深震的总体水平下降了0.2左右.浅震和深震的总体变化幅度小于二者的相对变化幅度.1959年以后,相对变化的成分十分显着.
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QUANTITATIVE STUDIES OF GLOBAL SEISMICITY(1)--TEMPORAL VARIATIONS OF GLOBAL SHALLOW AND DEEP SEISMIC ACTIVITY |
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| Affiliation: | Institute of Geophysics, State Setsmological Bureau |
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| Abstract: | The authors previously introduced a parameter A(b) to describe the level of seismic activity. It is named seismicity index. In this paper, A(b) is used to show the temporal variation of global seismicity by assigning an index number to each year up to the beginning of the 20th century. The magnitude data in catalogues of global earthquakes prepared by Duda and Abe were used to calculate the seismicity index. It has been found that the seismicity level derived from Duda's data is much higher than that derived from Abe's, especially for the time interval 1964-1977. The authors thought that it would be better to choose the Abe's catalogue as the principal basis to conduct the calculation.The secular variation of A(b) in the 20th century is a slow decrease with short period fluctuations. Maybe the variation belongs to a descending branch of a long-term periodic variation, which has a period of hundreds of years. The most dominant feature of A(b) of global shallow earthquakes is that there was a sudden drop of A(b) in the time interval of 1952-1955, and this kind of sudden drop of A(b) for deep and intermediate earthquakes happened in 1950-1952. The variations of shallow and deep (including intermediate) seismicity are nearly synchronous before the 1950-1955 sudden drops, and after that time interval the variation tendencies appear to be opposite and complementary to each other. This phenomenon may probably lead to the supposition that the earthquake potential energy storage controls the seismicity pattern from the earth's interior. |
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