Quantifying the features of earthquake clusters in north-Central Iran, based on nearest-neighbor distances and network analysis

IF 2.4 3区 地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS
Mohammad Talebi , Mehdi Zare , Antonella Peresan
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引用次数: 0

Abstract

The statistical features of earthquake clusters in North-Central Iran (Tehran Region) are investigated, with the aim of quantitatively characterizing the properties of earthquake triggering and allow exploring their possible relations with the tectonic setting of the study area.

The nearest-neighbor approach is used for the identification of the earthquake clusters in the space-time-energy domain. This approach permits for a data-driven identification of clusters so that, within multi-event clusters, the features of secondary and higher orders dependent events can be explored. The study is based on a revised dataset that is extracted from the catalog compiled by the Iranian Seismological Center (IRSC) for the period of 1996–2022. In order to exclude the effect of non-tectonic events, which turn out quite numerous within the study region, explosions within quarry-rich areas are removed; the identification of non-tectonic events is performed by considering the normalized ratios of daytime to nighttime events in an iterative removal procedure. According to preliminary analysis of the resulting catalog, an area is selected, within which a satisfactory completeness level is assessed for events with magnitude >2.0. Robust values of the scaling parameters, namely the b-value and the fractal dimension of epicenters, are also computed and are used to calculate the nearest-neighbor distances and to identify the earthquake clusters.

The nearest-neighbor method also permits to investigate the internal structure of earthquake sequences, and to differentiate the spatial properties of seismicity according to the different topological features of the clusters structure. The obtained results allow us identifying two macro-areas, approximately separated by the 52°E meridian, which are characterized by different clustering features, namely: high complexity indexes, indicating simple (burst-like) structure of clusters, to the East; low complexity index, corresponding to complex multi-level (swarm-like) structure of clusters, to the West. The complexity measures, borrowed from network theory (i.e. the Closeness and Outdegree Centralization indexes), consistently capture the complexity of the identified clusters, and confirm that the cluster structures have distinct preferred geographic locations. The territorial heterogeneity of the examined clustering properties can be related with the spatial variability of tectonic, structural and geophysical features of the Alborz region, in good agreement with findings from the Alps-Dinarides junction (Northeastern Italy), a region also characterized by a contractional structural setting, mainly including reverse and strike-slip faulting systems, and by moderate to high seismic activity.

Abstract Image

根据近邻距离和网络分析量化伊朗中北部地震群的特征
对伊朗中北部(德黑兰地区)地震群的统计特征进行了研究,目的是定量描述地震触发的特性,并探索其与研究地区构造环境的可能关系。这种方法允许以数据为导向识别地震群,从而在多事件地震群中探索次生和高阶依赖事件的特征。这项研究基于从伊朗地震中心(IRSC)编制的 1996-2022 年目录中提取的修订数据集。为了排除非构造事件的影响(非构造事件在研究区域内相当多),剔除了采石场丰富区域内的爆炸事件;在迭代剔除程序中,通过考虑白天与夜间事件的归一化比率来识别非构造事件。根据对所得目录的初步分析,选定了一个区域,在该区域内评估震级为 2.0 的事件的完整程度是否令人满意。最近邻方法还可以研究地震序列的内部结构,并根据震群结构的不同拓扑特征来区分地震的空间属性。根据所获得的结果,我们可以确定两个大区域,它们大致被东经 52 度经线分隔,具有不同的聚类特征,即:东边的复杂性指数高,表明聚类结构简单(类似于爆发);西边的复杂性指数低,对应于聚类结构复杂的多层次(类似于蜂群)。从网络理论中借鉴的复杂性度量(即 "接近度 "和 "外度数中心化指数"),始终如一地反映了已识别集群的复杂性,并证实集群结构具有独特的首选地理位置。所研究的聚类属性的地域异质性可与阿尔伯兹地区的构造、结构和地球物理特征的空间变异性联系起来,这与阿尔卑斯山-迪纳里德斯交界处(意大利东北部)的研究结果十分吻合,该地区的特点也是收缩构造环境,主要包括逆断层和走向滑动断层系统,以及中度到高度的地震活动。
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来源期刊
Physics of the Earth and Planetary Interiors
Physics of the Earth and Planetary Interiors 地学天文-地球化学与地球物理
CiteScore
5.00
自引率
4.30%
发文量
78
审稿时长
18.5 weeks
期刊介绍: Launched in 1968 to fill the need for an international journal in the field of planetary physics, geodesy and geophysics, Physics of the Earth and Planetary Interiors has now grown to become important reading matter for all geophysicists. It is the only journal to be entirely devoted to the physical and chemical processes of planetary interiors. Original research papers, review articles, short communications and book reviews are all published on a regular basis; and from time to time special issues of the journal are devoted to the publication of the proceedings of symposia and congresses which the editors feel will be of particular interest to the reader.
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