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Ιdentification of spatiotemporal seismicity clusters in central Ionian Islands (Greece)
Physics of the Earth and Planetary Interiors ( IF 2.3 ) Pub Date : 2021-02-10 , DOI: 10.1016/j.pepi.2021.106675
Polyzois Bountzis , Anastasios Kostoglou , Eleftheria Papadimitriou , Vasileios Karakostas

The spatiotemporal evolution of seismicity of an accurately relocated earthquake catalog in the central Ionian Islands, Greece, is explored, by the systematic identification of the earthquake clusters over the period September 2016–December 2019. Manual waveform phase picking was the input for the relocation leading to 13,632 earthquakes that compose a data set with a completeness magnitude as low as Mc = 1.5. The clustering procedure engages a temporal stochastic point process, the Markovian Arrival Process (MAP), for an initial separation of the background seismicity from potential seismic excitations, using the changes in the seismicity rate and a density-based clustering algorithm, DBSCAN, for the detection of elevated spatial density areas. A high concentration of temporally persistent clusters is identified along the western coastline of Lefkada Island, in the parallel step-over faults between the two major fault branches of the Kefalonia Transform Fault Zone and in the Myrtos Gulf area in Kefalonia, which are spatially correlated to the positive static stress changes induced by the coseismic slip of the Mw6.5 November 17, 2015 Lefkada main shock. The method presented remarkable potential in the identification of clusters in 3-D space along with the seismicity migration during the temporal evolution of seismic sequences. Multiple secondary faults of the Kefalonia segment can be revealed and the dominant triggering mechanisms can be illuminated contributing towards the understanding of the regional faulting properties and mechanics, an outcome that cannot be achieved solely by studying the large earthquakes, due to their rarity. The temporal and spatial clustering properties of microseismicity shed light on the preparation phase of the large earthquakes as being part of this process, thus contributing to the seismic hazard assessment.



中文翻译:

爱奥尼亚中部岛屿(希腊)时空地震活动群的识别

通过系统地识别2016年9月至2019年12月期间的地震群,探索了希腊中部爱奥尼亚群岛中已精确定位的地震目录的地震活动的时空演变。组成数据集的低至M c的13632次地震 = 1.5。聚类过程使用时间随机性过程,即马尔可夫到达过程(MAP),利用地震活动率的变化和基于密度的聚类算法DBSCAN,将背景地震活动性从潜在的地震激励中初步分离出来。检测高空间密度区域。在莱夫卡达岛的西部海岸线,凯法利尼亚变换断层带的两个主要断层分支和凯法利尼亚岛的迈尔托斯海湾地区,在平行的跨断层断层中发现了高度集中的时间持久性团簇,这些空间断层与M w同震滑动引起的正静应力变化6.5 2015年11月17日,莱夫卡斯州主震。该方法在识别3D空间团簇以及地震序列时间演化过程中的地震活动性迁移方面具有巨大潜力。可以揭示凯法利尼亚段的多个次生断层,并且可以阐明主要的触发机制,有助于了解区域断层的性质和力学,由于其罕见性,仅通过研究大地震是无法实现的。作为该过程的一部分,微地震的时空聚类性质为大地震的准备阶段提供了启示,从而有助于地震危险性评估。

更新日期:2021-02-15
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