Earthquake Declustering Using the Nearest‐Neighbor Approach in Space‐Time‐Magnitude Domain
Earthquake Declustering Using the Nearest‐Neighbor Approach in Space‐Time‐Magnitude Domain
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DOI：
10.1029/2018jb017120
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发表时间：
2020-04
期刊：
影响因子：
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通讯作者：
I. Zaliapin;Y. Ben‐Zion
中科院分区：
文献类型：
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作者：
I. Zaliapin;Y. Ben‐Zion
介绍了一种基于地震活动性最近邻分析的地震目录聚类算法。该算法通过随机细化来区分背景事件和聚类事件，根据空间变化的阈值去除事件。阈值是使用随机重组的目录来估计的，这些目录是静止的，具有独立的空间和时间成分，并保留了原始目录的空间分布。流行病型余震序列模型生成的目录分析表明，该算法正确分类了80%以上的背景和聚类事件，正确重建了平稳和空间相关的背景强度，并且在随机实现方面表现出很高的稳定性（超过75%的事件在超过90%的随机实现中具有相同的估计类型）。将该算法应用于2000-2015年全球北加州震级≥4级地震数据中心目录；1981-2017年期间，南加州的m≥2.5和3.5；1981—2015年，在1992年兰德斯断裂带附近，m≥0.0的区域；1984-2014年，圣安德烈亚斯断层Parkfield段m≥1.0。对全球星表和南加州星表（震级范围为Δm 4）估计的背景事件进行的几项测试并没有否定平稳性和时空独立性的零假设。与零点的偏差主要是由于地震活动性的局部时间波动和分区间的活动转换所致；它们可以追溯到原始目录，并代表了背景地震活动的真实特征。
We introduce an algorithm for declustering earthquake catalogs based on the nearest‐neighbor analysis of seismicity. The algorithm discriminates between background and clustered events by random thinning that removes events according to a space‐varying threshold. The threshold is estimated using randomized‐reshuffled catalogs that are stationary, have independent space and time components, and preserve the space distribution of the original catalog. Analysis of catalog produced by the Epidemic Type Aftershock Sequence model demonstrates that the algorithm correctly classifies over 80% of background and clustered events, correctly reconstructs the stationary and space‐dependent background intensity, and shows high stability with respect to random realizations (over 75% of events have the same estimated type in over 90% of random realizations). The declustering algorithm is applied to the global Northern California Earthquake Data Center catalog with magnitudes m ≥ 4 during 2000–2015; a Southern California catalog with m ≥ 2.5, 3.5 during 1981–2017; an area around the 1992 Landers rupture zone with m ≥ 0.0 during 1981–2015; and the Parkfield segment of San Andreas fault with m ≥ 1.0 during 1984–2014. The null hypotheses of stationarity and space‐time independence are not rejected by several tests applied to the estimated background events of the global and Southern California catalogs with magnitude ranges Δm 4. The deviations from the nulls are mainly due to local temporal fluctuations of seismicity and activity switching among subregions; they can be traced back to the original catalogs and represent genuine features of background seismicity.