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<p>The occurrence of clustered events has a certain impact on the understanding of seismic activity patterns. Moreover, most current declustering algorithms rely on the setting of thresholds. The settings of magnitude and clustering thresholds are two key factors affecting the declustering effect of the nearest-neighbor algorithm. Taking North China as a case study, we conducted a systematic test on the threshold parameters and analyzed the declustering effects under different threshold conditions and their impacts on seismic activity parameters. The research shows that as the magnitude threshold increases, the declustering rate decreases. The proportion of low-magnitude events as clustered events is relatively high, while high-magnitude events are mostly background events. The declustered <i>b</i>-value increases with the increase of the magnitude threshold. There are certain differences in the Poisson distribution characteristics under different thresholds. The clustering threshold is inversely proportional to the declustering rate. As the clustering threshold increases, the number of removed earthquakes decreases, resulting in an enhancement of the overall seismic activity, but it does not significantly change the relative spatial intensity. The clustering threshold is positively correlated with seismicity parameters <i>a</i>-value and <i>b</i>-value. The spatial variation of the <i>b</i>-value is relatively gentle. The phenomenon of low <i>b</i>-values appears in areas with complex seismic faults such as the Zhangjiakou-Bohai tectonic belt, which are still potential&#xa0;hazardous areas that need to be focused on in the future. An increase in the clustering threshold makes the spatial description of the <i>b</i>-value more detailed. There are certain commonalities in the low <i>b</i>-value areas, which also reflects that different clustering thresholds do not change the crustal stress state. Analyzing the influence of different threshold settings on the declustering rate and seismic activity parameters plays an important reference role in accurately grasping seismic activity characteristics and improving the accuracy and reliability of probabilistic seismic hazard analysis.</p>

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Analysis of threshold setting's impact on declustering efficiency and seismicity parameters in North China

  • 期刊论文

  • 发表日期：

    2025年9月15日

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  • Bi Jinmeng,
  • Cao Fuyang,
  • Sang Jianbin

摘要

The occurrence of clustered events has a certain impact on the understanding of seismic activity patterns. Moreover, most current declustering algorithms rely on the setting of thresholds. The settings of magnitude and clustering thresholds are two key factors affecting the declustering effect of the nearest-neighbor algorithm. Taking North China as a case study, we conducted a systematic test on the threshold parameters and analyzed the declustering effects under different threshold conditions and their impacts on seismic activity parameters. The research shows that as the magnitude threshold increases, the declustering rate decreases. The proportion of low-magnitude events as clustered events is relatively high, while high-magnitude events are mostly background events. The declustered b-value increases with the increase of the magnitude threshold. There are certain differences in the Poisson distribution characteristics under different thresholds. The clustering threshold is inversely proportional to the declustering rate. As the clustering threshold increases, the number of removed earthquakes decreases, resulting in an enhancement of the overall seismic activity, but it does not significantly change the relative spatial intensity. The clustering threshold is positively correlated with seismicity parameters a-value and b-value. The spatial variation of the b-value is relatively gentle. The phenomenon of low b-values appears in areas with complex seismic faults such as the Zhangjiakou-Bohai tectonic belt, which are still potential hazardous areas that need to be focused on in the future. An increase in the clustering threshold makes the spatial description of the b-value more detailed. There are certain commonalities in the low b-value areas, which also reflects that different clustering thresholds do not change the crustal stress state. Analyzing the influence of different threshold settings on the declustering rate and seismic activity parameters plays an important reference role in accurately grasping seismic activity characteristics and improving the accuracy and reliability of probabilistic seismic hazard analysis.