## 2 Materials and Methods
### Earthquake Catalog of the Eastern Sector of the Arctic Zone of the Russian Federation
\(M=b\)\(\times\)\(M_{\mathrm{L}}-a\), regression coefficients \(a\) and \(b\) are given in [16]. The formalized construction of the author's technique for merging earthquake catalogs is described in detail in [48]. The stages of merging the integrated catalog of the eastern sector of the Arctic zone of the Russian Federation and unifying the magnitude scales are described in [16]. The catalog is available to the public on the website of the World Data Center for Solid Earth Physics, Moscow, at [[http://www.wdcb.ru/arctic_antarctic/arctic_seism.html](http://www.wdcb.ru/arctic_antarctic/arctic_seism.html)]([http://www.wdcb.ru/arctic_antarctic/arctic_seism.html](http://www.wdcb.ru/arctic_antarctic/arctic_seism.html)), (accessed on 24 October 2022). The map of earthquake epicenters from the integrated catalog is presented in Figure 2.  
The catalog of strong earthquakes of the eastern sector of the Russian Arctic, starting from 1900, was formed based on 3 main sources: the integrated catalog [16], _New Catalog of Strong Earthquakes in the USSR from Ancient Times through 1977_ (hereinafter _\"New Catalog... \"_) [15] and the catalog of the International Seismological Center (ISC). It should be noted that in the _\"New Catalog...\"_[15] there are many cases when coordinates of strong earthquakes correspond to low-seismicity areas, according to modern instrumental data. In the description of the _\"New Catalog...\"_ it is said that _\"the least reliable is the assessment in the presence of intensity data in one observation site. In such cases, the value obtained under the assumption that the source was located under the given observation site at the average depth for the region was taken as its lower limit. The value corresponding to the epicenter at the nearest point of a large seismically active zone was taken as the upper limit, and the average was taken as the final estimate. The error in such cases could be two units.\"_  
Accordingly, it was decided not to include in the formed catalog of strong earthquakes the events with the accuracy of \(\pm 2\) of the indicated magnitude in the \"_New Catalog...\"_. Thus, 53 events were taken from the \"_New Catalog...\"_, given in the sections \"Arctic Basin,\" \"Chukotka,\" \"Kamchatka,\" and \"Yakutia and the North-East.\" At the same time, even though data from international agencies have already been used in compiling the \"_New Catalog_... \", we have identified several cases where the final magnitude estimate was lower than the available instrumental estimate. In such cases, preference was given to the highest magnitude, namely, the recalculated \(M_{\rm S}\) according to the ISC data [53]. All events with \(M\geq 5.0\) were selected from the integrated instrumental catalog [16]. In this case, events with \(M_{\rm W}\geq 5.0\) or \(M_{\rm S}\geq 5.0\) were included in the formed catalog of strong earthquakes automatically, and \(M=M_{\rm w}\) or \(M=M_{\rm S}\), respectively. For events with \(mb\geq 5.0\), an additional check was carried out, after which such events fell into one of two categories:  
* If there was an estimate of \(M_{\rm S}\geq 5.0\), earthquakes were included in the formed catalog of strong events, and \(M=M_{\rm S}\), since the saturation effect of magnitudes for \(mb\geq 5.0\) is known. * If there was an estimate of \(M_{\rm S}<5.0\), earthquakes were not included in the catalog of strong earthquakes. Indeed, such a combination of \(M_{\rm S}\)-\(mb\) often corresponds to deep earthquakes, for which the applicability of the FCAZ method is not clear, since devastating consequences after deep events are observed rarely. Thus, the formed catalog of strong earthquakes includes 166 events with \(M\geq 5.0\). Due to the remoteness of many seismic stations from the studied region, as well as its relatively weaker seismicity, it was decided to consider earthquakes with \(M\geq 5.0\) for the studied region as strong.