## 2 Materials and Methods
### Earthquake Catalog of the Eastern Sector of the Arctic Zone of the Russian Federation  
The basis for the recognition of potential high seismicity zones by the FCAZ method is the most complete earthquake catalog of the studied region. In this paper, epicenters from the original, integrated earthquake catalog of the eastern sector of the Arctic zone of the Russian Federation are used as recognition objects. The catalog contains information on 23,254 seismic events for the period 1962-2020 [16]. It was created by the system analysis method as a result of a formalized combination of earthquake data from the regional catalogs of the Geophysical Survey of the Russian Academy of Sciences (GS RAS, [[http://www.gsras.ru/new/eng/catalog/](http://www.gsras.ru/new/eng/catalog/)]([http://www.gsras.ru/new/eng/catalog/](http://www.gsras.ru/new/eng/catalog/)), accessed on 1 October 2022) and the International Seismological Center (ISC, [[http://www.isc.ac.uk/](http://www.isc.ac.uk/)]([http://www.isc.ac.uk/](http://www.isc.ac.uk/)), accessed on 1 October 2022). Different seismic agencies can both register and skip events. This happens due to network configurations, the specifics of processing methods, as well as the procedures for transferring information to data centers. When catalogs are merged, the problem of identifying and removing the resulting duplicates naturally arises. The problem is complicated by the need to distinguish duplicates from aftershocks [47] since the latter are also events close in space and time. The problem of merging these catalogs was solved using the author's technique [48]. It is based on a modification of the nearest neighbor method [49, 50] for the recognition of duplicates. Namely, correspondence is built for events from two catalogs, after which earthquakes are classified into unique and duplicates using the Euclidean metric. Consistent application of the technique makes it possible to combine any number of earthquake catalogs [48]. When creating an integrated earthquake catalog of the eastern sector of the Arctic zone of the Russian Federation [16], the following were sequentially combined:  
* The regional catalog of Xavutia from the annual journal \"Earthquakes in Northern Eurasia\"
* The regional catalog of the northeast of Russia from the annual journal \"Earthquakes in Northern Eurasia\"
* The earthquake catalog of Kamchatka of the Kamchatka Branch of GS RAS
* The ISC catalog, which is a composite catalog containing data from many world and Russian agencies  
Different agencies define, generally speaking, different magnitude types of seismic events. At the same time, for a rigorous formulation of the problem of earthquake-prone areas recognition, which is determined by the threshold \(M_{0}\), it is necessary to provide all records of the catalog with a magnitude of the same type. In this regard, the magnitude scale in the integrated catalog was unified [16]. This was undertaken for the first time with the problems of the FCAZ cycle. This was a fundamental step forward in the development of the system analysis method. When analyzing various magnitude scales, preference is usually given to the moment magnitude: \(M=M_{\mathrm{W}}\)[16, 51, 52]. In the integrated catalog, \(M_{\mathrm{W}}\) was defined only for earthquakes with \(M>5.0\). For events with magnitudes up to \(M\approx 4.0\), the magnitude \(mb\) was mainly defined, and in such cases, \(M=mb\). Weak earthquakes had magnitudes defined by local networks, with a large variety in their types [16]. Most of the weak earthquakes had an energy class estimate, and only for 7% of the events were other types of magnitude calculated. In this regard, the following magnitude priority system was used in the integrated catalog [16]:  
1. \(M=M_{\mathrm{W}}\)\({}^{\mathrm{GCMT}}\) or
2. \(M=M_{\mathrm{S}}\)\({}^{\mathrm{ISC}}\) for strong earthquakes before 1976 or
3. \(M=mb\)\({}^{\mathrm{ISC}}\) or
4. \(M=b\)\(\times\)\(K_{\mathrm{S}}-a\), regression coefficients \(a\) and \(b\) are given in [16]
5.