REPRESENTATIVENESS EVOLUTION OF THE EARTHQUAKE’S CATALOGS GS RAS CONTINENT-OCEAN TRANSITION ZONE FOR 2003–2021

Resumo

The author gives evaluation of seismic transitional zone continent-ocean catalogs representativeness using the FIC EGS RASsummary 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 magnitudesharp increase marks the boundary of  seismic zonesobservations: 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.