Representativeness evolution of the earthquake’s catalogs GS RAS continent-ocean transition zone for 2003-2021

The author gives evaluation of seismic transitional zone continent-ocean catalogs representativeness using the FIC EGS RAS summary data (Obninsk) for the period of 2003-2021. In the investigation process it has been compiled a map of the minimum representative magnitude, characteristic of the Far Eastern region. It emphasizes that a significant portion of area in the Russian Far East has a lower threshold of earthquake representation with magnitudes ranging from 1.8 to 2.0. The representative magnitude sharp increase marks the boundary of seismic zones observations: the Sakhalin network on the border with China, the Magadan and Kamchatka networks on the Chukotka Peninsula. When comparing the periods of 2003-2015 and 2003-2021, the overall pattern of representative magnitude distribution remains consistent. In the regions with a sparse station distribution within the seismic monitoring network, new seismic stations show changes in the minimum threshold of representative magnitude. In the southern Far East, there is a decrease in the representative magnitude threshold, also noted in the northern part of Sakhalin and the Kuril Islands. The accuracy of determining the upper crustal earthquakes (range of depths 0-20 km) hypocenters depths in the Amur region is an average of ± 1.8 km, and in the Okhotsk Sea region - ± 2.5 km. At the same time, the accuracy of estimations in the lower crustal layer (range of depths 21-50 km) is ± 3.8 km in the Middle Amur Region, and ± 7.7 km in the Okhotsk Sea region. It is found a significant reduction in the measurement error of earthquakes hypocenters depths determining, as compared to the period of 2003- 2015.