Lippiello Eugenio, Godano Cataldo, de Arcangelis Lucilla
Department of Mathematics and Physics, University of Campania "L. Vanvitelli", Viale Lincoln 5, 81100 Caserta, Italy.
Department of Engineering, University of Campania "L. Vanvitelli', Via Roma 29, 81031 Aversa (CE), Italy.
Entropy (Basel). 2019 Feb 13;21(2):173. doi: 10.3390/e21020173.
An increase of seismic activity is often observed before large earthquakes. Events responsible for this increase are usually named foreshock and their occurrence probably represents the most reliable precursory pattern. Many foreshocks statistical features can be interpreted in terms of the standard mainshock-to-aftershock triggering process and are recovered in the Epidemic Type Aftershock Sequence ETAS model. Here we present a statistical study of instrumental seismic catalogs from four different geographic regions. We focus on some common features of foreshocks in the four catalogs which cannot be reproduced by the ETAS model. In particular we find in instrumental catalogs a significantly larger number of foreshocks than the one predicted by the ETAS model. We show that this foreshock excess cannot be attributed to catalog incompleteness. We therefore propose a generalized formulation of the ETAS model, the ETAFS model, which explicitly includes foreshock occurrence. Statistical features of aftershocks and foreshocks in the ETAFS model are in very good agreement with instrumental results.
在大地震之前，通常会观测到地震活动增加。导致这种增加的事件通常被称为前震，其发生可能代表了最可靠的前兆模式。许多前震的统计特征可以根据标准的主震到余震触发过程来解释，并在震后序列的流行病类型（ETAS）模型中得到重现。在这里，我们对来自四个不同地理区域的仪器地震目录进行了统计研究。我们关注四个目录中前震的一些共同特征，而这些特征无法由ETAS模型重现。特别是，我们发现在仪器目录中前震的数量明显多于ETAS模型预测的数量。我们表明，这种前震过剩不能归因于目录不完整。因此，我们提出了ETAS模型的广义公式，即ETAFS模型，该模型明确包括前震的发生。ETAFS模型中余震和前震的统计特征与仪器观测结果非常吻合。
