# Integrated Earthquake Catalog of the Eastern Sector of the Russian Arctic
## 3 Results
### Merging Catalogs
#### 3.1.4 Stage 4  
Merging RUS_ISC and CORE  
As the main catalog selected, CORE includes events from the ISC catalog with the magnitudes \(M_{\rm W}\)\({}^{\rm GCMT}\) or \(m\)\({}^{\rm ISC}\). As an additional catalog, we consider RUS_ISC, obtained at the previous stage. The preliminary analysis of the duplicates was performed with the standard catalog distribution parameters \(\sigma_{T}=0.05\) min, \(\sigma_{X}=15\) km, and \(\sigma_{Y}=15\) km. Approximately 1000 duplicates were identified and used to determine the variances. It was verified that each of the parameters follows a normal distribution and that the mean is small compared to the standard deviation for all three parameters (\(DT\), \(DX\), and \(DY\)). It was also verified that the variance is almost independent of the event magnitude and time (Figure 10).  
The final analysis of the duplicates was performed with the parameters \(\sigma_{T}=0.044\) min and \(\sigma_{X}=\sigma_{Y}=18.3\) km. The metric values between the events of the CORE catalog were also calculated. This made it possible to estimate the probability that the duplicate was chosen incorrectly due to the high density of earthquakes.  
The value \(Ro=5.9\) was chosen as a threshold (Figure 11). In this case, 1011 duplicates are detected. In total for the studied territory, there are 21,987 unique events in the RUS_ISC catalog. These events were added to the CORE catalog, and a combined ARCTIC catalog containing 23,370 events was obtained. Figure 12 shows the space-time structure of the CORE/RUS_ISC duplicates and the naturally grouped events in the CORE catalog. The metric level lines \(Ro=5.9\) and \(Ro=8.4\) provide close-to-optimal separation of the duplicates and naturally grouped events (the lower cluster of black dots).  
Figure 9: Distribution of normalized \(DT\) and \(DR\), and metric level lines (1). The colored dots are the RUS/ISC_Other pairs and the black dots are the distances between the RUS/RUS events in metric (1). The metric levels \(Ro=6\) and \(Ro=7.6\) are shown by the black lines, and absolute duplicates are not shown.  
Figure 11: (**a**) Comparison of the distribution of the metric for the CORE/RUS_ISC pairs (blue histogram) and the same metric for the CORE/CORE earthquakes (red histogram). (**b**) Threshold optimization: the red line is the probability of missing a duplicate in the model with metric (1), the blue line is the probability of a false duplicate, the black line is the total probability of errors of the first and second kind, the dashed line \(Ro=5.9\) corresponds to an equal number of errors of the first and second kind (number of false duplicates is equal to the number of missed duplicates), the estimate of the total number of errors is approximately 0.4%, and the gray bar shows the range of values of the metric \(Ro=6.5\div 8.4\), minimizing the total number of errors (approximately 0.3%).  
Figure 10: Distributions of \(DT\), \(DX\), and \(DY\) for the nearest events from the CORE/RUS_ISC catalogs, and the dependence of the standard deviations \(\sigma_{T}\), \(\sigma_{X}\), and \(\sigma_{Y}\) and the mean values \(\overline{DT}\), \(\overline{DX}\), and \(\overline{DY}\) on the time and magnitude of the events. The red dots and bars are the population mean values and standard deviations, respectively.