Integrated Earthquake Catalog of the Eastern Sector of the Russian Arctic

Abstract

The objective of this study was to create a representative earthquake catalog for the Eastern Sector of the Arctic zone of the Russian Federation that combines all available data from Russian and international seismological agencies, with magnitude reduction to a uniform scale. The article describes the catalog compilation algorithm, as well as formalized procedures for removing duplicates and choosing the optimal magnitude scale. Due to different network configurations and record processing methods, different agencies may register/miss different events. This results in the absence of some events in different earthquake catalogs. Therefore, merging the data of various seismological agencies will provide the most complete catalog for the studied region. When merging catalogs, the problem of identifying duplicates (records related to the same seismic event) necessarily arises. An additional difficulty arises when distinguishing between aftershocks and duplicates since both are events that are close in space and time. To solve this problem, we used a modified nearest neighbor method developed earlier by the authors. The modified version, which is focused on identifying duplicates and distinguishing between duplicates and aftershocks, uses a probabilistic metric in the network error space to determine the epicenters and times of seismic events. In the present paper, a comparison and regression analysis of the different magnitude types of the integrated catalog is carried out, and based on the obtained ratios, the magnitude estimates are unified.

Integrated Earthquake Catalog of the Ossetian Sector of the Greater Caucasus

“…As noted above, the author's method, used in the present study to identify duplicates that arise when earthquake catalogs are sequentially merged, is described in detail in [1] (see Supplementary Materials). The application of this method to create the most complete earthquake catalog with a unified magnitude scale for the Arctic zone of the Russian Federation is given in [4][5][6]. For this reason, a description of the method is not provided in this article.…”

“…When merging catalogs, the preference is given to earthquake records from the ISC catalog that have magnitude definitions MW GCMT and/or mb ISC and/or mb NEIC [4][5][6]. As shown in Table 1, in the region considered, a large majority of seismic events are registered by GS RAS seismic networks.…”

“…This refers not only to the ISC catalog but also to the GSR catalogs, which combine data from regional networks of North Ossetia, Dagestan, Georgia, and the GS RAS teleseismic network. In this situation, the application of the method used in [4,5] to determine the threshold value of the metric leads to an increased probability of missing duplicates. Therefore, in the present paper the actual distribution of the metric for the nearest events from the two catalogs being merged is used instead of the multivariate normal distribution model.…”

“…Red lines in Figures 5b, 7b and 9b show the value 1 − Fdub, which is considered to be the probability of missing a duplicate (error of the I kind). The probability of a false duplicate (error of the II kind) is estimated in the same way as in [4,5]. For this reason, the values of the metric (1) Ro between events inside the additional catalog are calculated: blue lines in Figures 5b, 7b and 9b show the fraction of events with proximity less than a given Ro value.…”

“…It allows the identification and removal of duplicate events that occur when the catalogs are merged. Previously, the integrated catalog was elaborated for the Arctic zone of the Russian Federation [4][5][6]. It is demonstrated that merging catalogs of various global, national, and regional seismic networks makes it possible to improve the completeness and representativeness of seismic events in the studied region [7][8][9][10].…”