# Integrated Earthquake Catalog II: The Western Sector of the Russian Arctic
## 3 Results
### Magnitudes in the Integrated Catalog of the Western Sector of the AZRF
#### 3.2.1 The Kola Peninsula and Karelia  
There is no earthquake in the Kola Peninsula and Karelia with a determined \(M\)\(w\)GCMT magnitude, while only seven events have \(m\)\(b\)\({}^{\text{ISC}}\) and \(m\)\(b\)\({}^{\text{NEIC}}\) magnitude estimates (Figure 1). Due to these reasons, direct magnitude unification to the moment magnitude scale is impossible. Most events have local \(ML\) magnitudes from various agencies. \(ML\)\({}^{\text{KOLA}}\) was chosen as the base local magnitude because the local network of the Kola branch of GS RAS is located directly in the studied area. However, most earthquakes have local \(ML\)\({}^{\text{HEL}}\) magnitudes, allowing for more reliable correlations with other magnitude types (Figure 11). Thus, the unified local magnitude \(ML\) is determined by a regression relationship with \(ML\)\({}^{\text{HEL}}\), which is approximately 0.3 less than \(ML\)\({}^{\text{KOLA}}\) (Figure 11a). Figure 10: Analysis of the W_ARCTIC catalog: (**a**) Red histogram—number of events per year (blue histogram shows a similar distribution for the VEP catalog); (**b**) Spatial distribution of epicenters; (**c**) Space–time distribution of events. Red dots represent explosions from the ISC_EXP catalog, while black dots represent earthquakes from the merged W_ARCTIC catalog in the Kola Peninsula and Karelia (60\({}^{\circ}\) N–72\({}^{\circ}\) N, 25\({}^{\circ}\) E–40\({}^{\circ}\) E). Out of 104 events with \(\mathit{MPSP}^{\mathrm{VEP}}\) magnitude, only two have \(\mathit{ML}^{\mathrm{HEL}}\) and \(\mathit{mb}^{\mathrm{ISC}}\) magnitudes. To refine the magnitude relationships, events outside the region (Svalbard) were used (Figure 12). Two events from the studied region fit well into the regression for Svalbard events. For this reason, we used the obtained relationships for earthquakes in the Kola Peninsula and Karelia. All events with \(\mathit{MPSP}^{\mathrm{VEP}}\) magnitude occurred in 1987-1989. It was previously suggested that not all explosions and other non-earthquake events were removed from the catalog for this period. Therefore, it is possible that these events are not tectonic earthquakes. In addition, most events have \(\mathit{MPSP}^{\mathrm{VEP}}\) < 3.5 magnitudes; i.e., they are outside the range for which relationships are established. Therefore, they were considered highly unreliable. Only \(\mathit{MD}^{\mathrm{HEL}}\) and \(\mathit{MD}^{\mathrm{BER}}\) duration magnitudes have 166 events. This type of magnitude is often used for records without clear arrival (explosions, landslides, etc.). For example, the \(\mathit{ML}\) and \(\mathit{MD}\) relationship is sometimes used to identify landslides in regional catalogs [35]. Events with this type of magnitude are only present in the catalog during the period 1988-1997 when explosions are presumably not removed. It should be noted that \(\mathit{ML}^{\mathrm{HEC}}\) and \(\mathit{mb}^{\mathrm{HPS}}\) magnitudes appear in the catalog only during this period, for which  
Figure 11: Shift-type correlation ratio for local magnitudes from various agencies in the Kola Peninsula and Karelia sub-region. Magnitude types are specified on the figures. All eight relationships appear reliable. Figure 12: Shift-type correlation ratio for \(\mathit{MPSP}^{\mathrm{VEP}}\) magnitude. Magnitude types are specified on the figure. Gray dots are events in Svalbard; black dots are two events in the shelf sub-region. indirect correlations through \(MD^{\text{BER}}\) were used for unification (Figure 13). Thus, it was assumed that most of these events are not earthquakes. The regression ratios could not be established for eight events. A relationship was determined between the unified local magnitude \(ML\) and \(mb^{\text{JSC}}\), \(mb^{\text{NEC}}\): \(ML=mb-0.08\), i.e., they are very close. In fact, the difference lies within the 95% confidence interval, and they can be considered equal. There are only five events with both types of magnitudes, but they fit very well on a straight line (Figure 14).