The classical procedure of the Probabilistic Seismic Hazard Analysis (PSHA) requires a Poissonian distribution of earthquakes. Seismic catalogs follow a Poisson distribution just after the application of a declustering algorithm that leaves only one earthquake for each seismic sequence (usually the stronger, i.e. the main shock). Removing earthquakes from the seismic catalogs leads to underestimation of the annual rates of the events and consequently associate with low seismic hazard as indicated by several studies. In this study, we aim investigating the performance of two declustering methods on the Italian instrumental catalog and the impact of declustering on estimation of the b-value and on the seismic hazard analysis. To this end, first the spatial variation in the seismicity rate was estimated from the declustered catalogs using the adaptive smoothed seismicity approach, considering small earthquakes (M_w≥ 3.0). We then corrected the seismicity rates using new approach that allows for counting all events in the complete seismic catalog by simply changing the magnitude frequency distribution. The impact of declustering on seismic hazard analysis is illustrated using PSHA maps in terms of peak ground acceleration (PGA) and spectral acceleration (SA) in 2 s, with 10 per cent and 2 per cent probability of exceedance in 50 years, for Italy. We observed that the hazard calculated from the declustered catalogs was always lower than the hazard computed using the complete catalog. These results are in agreement with previous results obtained in different parts of the world.

中文翻译：

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PSHA的良好做法：聚类，b值估计，前震和余震包括在内；意大利的案例研究

概率地震危险性分析（PSHA）的经典程序需要地震的泊松分布。在应用去簇算法后，地震目录遵循泊松分布，该算法对每个地震序列仅留下一次地震（通常较强，即主震）。从地震目录中删除地震会导致低估事件的年发生率，因此，如若干项研究所示，地震危险性较低。在这项研究中，我们旨在调查意大利乐器目录中两种降噪方法的性能以及降噪对b-估计值的影响值和对地震危害的分析。为此，首先在地震活动率的空间变化是从declustered目录使用自适应平滑地震活动的方法，考虑小地震（M估计_瓦特≥3.0）。然后，我们使用新方法校正了地震活动率，该方法允许通过简单地改变幅度频率分布来计数完整地震目录中的所有事件。在意大利，使用PSHA映射以2 s内的峰值地面加速度（PGA）和频谱加速度（SA）表示了减震对地震危险性分析的影响，其在50年内超过10％和2％的概率。我们观察到，从分散目录中计算出的危害始终低于使用完整目录中计算出的危害。这些结果与世界各地获得的先前结果一致。