# Integrated Earthquake Catalog of the Eastern Sector of the Russian Arctic
## 2 Materials and Methods
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Agency** & **Agency** & **Number of Earthquakes with** \\
**Abbreviation** & **Energy Classes and/or Magnitudes * \\ \hline AEIC & Alaska Earthquake Information Center, USA & 184 \\ \hline ANDRE & USSR & 16 \\ \hline ANF & USAArray Array Network Facility, USA & 2 \\ \hline BJI & China Earthquake Networks Center, China & 1 \\ \hline BYKL & Baykal Regional Seismological Centre, GS SB RAS, Russia & 4 \\ \hline DNAG & USA & 13 \\ \hline EIDC & Experimental (GSETT3) International Data Center, USA & 22 \\ \hline GCMT & The Global CMT Project, USA & 1 \\ \hline IDC & International Data Centre, CTBTO, Austria & 123 \\ \hline ISC & International Seismological Centre, United Kingdom & 1507 \\ \hline KRSC & Kamchatka Branch of the Geophysical Survey of the RAS, Russia & 2684 \\ \hline MATSS & USSR & 1400 \\ \hline MOS & Geophysical Survey of Russian Academy of Sciences, Russia & 26 \\ \hline MSUGS & Michigan State University, Department of Geological Sciences, USA & 2585 \\ \hline NEIC & National Earthquake Information Center, USA & 192 \\ \hline NEIS & National Earthquake Information Service, USA & 1 \\ \hline NERS & North Eastern Regional Seismological Centre, GS RAS, Russia & 4688 \\ \hline NKSZ & USSR & 8 \\ \hline SBDV & USSR & 107 \\ \hline SYKES & Sykes Catalogue of earthquakes 1950 onwards & 2 \\ \hline USCGS & United States Coast and Geodetic Survey, NEIC, USA & 1 \\ \hline WASN & USA & 328 \\ \hline YARS & Yakutiya Regional Seismological Center, GS SB RAS, Russia & 2256 \\ \hline ZEMSU & USSR & 1884 \\ \hline  & Total: & 18,035 \\ \hline \hline \end{tabular}  
* The ISC catalog contains 6441 events with unknown energy classes and magnitudes.  
\end{table} 
Table 2: ISC catalog statistics from 1962–2020. Earthquakes from the ISC global catalog (the abbreviation of the ISC and GCMT agency in Table 2) with the magnitudes \(M_{\rm W}{}^{\rm GCMT}\) and/or \(mb^{\rm ISC}\) are the core (hereinafter CORE) (1393 events);
2. Earthqu from Russian catalogs with local estimates for the magnitude of weak events. In the intersection zones, preference is given to the data from the catalog of Yakutia (Table 1);
3. Other earthquakes from the ISC (abbreviation of the ISC agency in Table 2, without the magnitude data \(M_{\rm W}{}^{\rm GCMT}\) or \(mb^{\rm ISC}\)), as well as data from other agencies in the ISC catalog (16,642 events). This selection from the ISC catalog will be further denoted by ISC_Other. To discriminate and remove duplicates resulting from the merging of catalogs, we apply the modified nearest neighbor method and the Euclidean metric in the space of the variance in the definitions of seismic event parameters by different networks [34]. We apply a basic three-parameter model that takes into account the differences in time and the coordinates of the epicenter, the effectiveness of which was shown in [34]. We do not analyze the difference in depth because for a significant number of events, information on the hypocentral depth is not presented in the original catalogs or a standard value of 10 km is given. The magnitude is also excluded from consideration because different catalogs use different types of magnitude. At the input, there are two catalogs: main Catalog 1 and additional Catalog 2. We believe that neither Catalog 1 nor Catalog 2 contain duplicates within themselves, since the modern automatic processing of seismic records almost completely eliminates technical errors. The problem is to find records in Catalogs 1 and 2 that will correspond to the same seismic events (duplicates) and divide Catalog 2 into events that have duplicates in Catalog 1 and unique events. A modification of the nearest neighbor method is based on the assumption that duplicates form pairs in which the events must belong to different source catalogs. As a result of applying the modified nearest neighbor method, a set of pairs of potential duplicates is formed.