Bi Jinmeng, Cao Fuyang, Ma Yong
Tianjin Earthquake Agency, Tianjin, China.
Institute of Geophysics, China Earthquake Administration, Beijing, China.
PLoS One. 2025 Jul 21;20(7):e0327295. doi: 10.1371/journal.pone.0327295. eCollection 2025.
To explore the effect of the cut-off magnitude on the declustering of earthquake sequences, the calculation of seismicity parameters, the earthquake occurrence rate, and the hazard level of North China at present, we employed a stochastic declustering method based on the spatio-temporal ETAS model to decluster under different the cut-off magnitudes. And we have undertaken comprehensive research on the declustered distribution characteristics, seismicity parameters, and earthquake occurrence rates. The research results show that the selections of the cut-off magnitudes can lead to certain differences in the declustering results. As the cut-off magnitude increases, the declustering rate shows a certain downward trend, and the Poisson characteristics become more prominent. The stochastic declustering method does not significantly change the spatio-temporal statistical characteristics of seismicity parameters. Combining the analysis of the spatial distribution of the background earthquake occurrence rate, low b-value, and clustering rate in North China under different cut-off magnitudes, we found that regions including the intersection area of the Zhangjiakou-Bohai seismic belt and the Tanlu seismic belt, and the western part of the northern margin of the Ordos have relatively high seismic hazard. Some seismic belts, including the Zhangjiakou-Bohai seismic belt, exhibit a correlation among relatively high background seismicity, high crustal strain rate, and strong earthquakes. We can provide basic sequence data and technical support for the judgment of the dangerous state of moderate and strong earthquakes. This will further enhance our understanding of the laws of seismic activities in North China.
为了探究截止震级对地震序列去丛集化、地震活动性参数计算、目前华北地区地震发生率及危险水平的影响，我们采用基于时空ETAS模型的随机去丛集化方法在不同截止震级下进行去丛集化。并且我们对去丛集化后的分布特征、地震活动性参数及地震发生率进行了全面研究。研究结果表明，截止震级的选择会导致去丛集化结果存在一定差异。随着截止震级增大，去丛集化率呈一定下降趋势，泊松特征更加突出。随机去丛集化方法对地震活动性参数的时空统计特征改变不明显。结合不同截止震级下华北地区背景地震发生率、低b值及丛集率的空间分布分析，我们发现张家口—渤海地震带与郯庐地震带交汇区域以及鄂尔多斯北缘西段等地区地震危险性相对较高。包括张家口—渤海地震带在内的一些地震带，相对较高的背景地震活动性、较高的地壳应变率与强震之间存在相关性。我们可为中强震危险状态判断提供基础序列数据及技术支持。这将进一步加深我们对华北地区地震活动规律的认识。
