Seismic moment distribution
Seismic moment distribution
复制标题
地震矩分布
DOI：
10.1111/j.1365-246x.1991.tb04606.x
复制
发表时间：
1991
期刊：
影响因子：
--
通讯作者：
Y. Kagan
中科院分区：
文献类型：
--
作者：
Y. Kagan
我们回顾了在确定地震规模时可能出现的错误。我们建议，规模分布可以有效地定义只有地震序列，而不是“个别”地震。误差分析的结果是，我们对许多报道的δ值与构造和地震活动时空特征之间相关性的有效性提出质疑。地震矩分布的研究在很大程度上避免了这些误差和偏差的影响，因而比标准的震级-频率规律分析优越上级。应用伽玛分布描述地震序列的地震矩分布。该分布推广了著名的Gutenberg-Richter（G-R）关系，其特征在于两个参数。我们使用最大似然法来确定不同深度范围内全球地震的伽马分布参数。经验分布是从哈佛小组编制的力矩-张量目录中导出的。地震序列的标量地震矩的p值（类似于G-R震级-频度定律中的6值）对于所有地震都接近1/2，这是地震活动性临界分支模型预测的值。这一结果将得到改善，因为更多的地震矩数据变得可用，提供输入的地震活动性模型的基础上渗流或自组织临界模型。如果/3等于1/2，那么使用临界分支模型，我们发现现有目录中的大多数小地震都是相关地震，即，余震即使在中等震级的地震中，相关事件的数量也可能超过独立事件的数量。
SUMMARY We review possible errors in determining the size of earthquakes. We propose that the size distribution can be effectively defined only for earthquake sequences, not for ‘individual’ earthquakes. As a result of the error analysis, we question the validity of many reported correlations between the 6-value and spatio-temporal characteristics of tectonics and seismicity. The study of the distribution of earthquake seismic moment largely avoids the influence of these errors and biases, and is therefore superior to the standard analysis of the magnitude-frequency law. The gamma distribution is applied to describe the distribution of seismic moments of earthquake sequences. This distribution which generalizes the well-known Gutenberg-Richter (G-R) relation, is characterized by two parameters. We use the maximum likelihood method to determine the parameters of the gamma distribution for worldwide earthquakes in different depth ranges. The empirical distribution is derived from the moment-tensor catalogue compiled by the Harvard group. The p-value for scalar seismic moment of earthquake sequences (an analogue of the 6-value in the G-R magnitude-frequency law) is close to 1/2 for all earthquakes, the value predicted by a critical branching model of seismicity. This result which will be improved as more seismic moment data become available, provides input for modelling of seismicity based on percolation or on self-organized criticality models. If /3 equals 1/2, then using the critical branching model we find that most small earthquakes in available catalogues are dependent shocks, i.e., aftershocks. Even among earthquakes of intermediate magnitudes, the number of dependent events may exceed that of independent events.