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The article is a continuation of the research on creating the most complete and representative earthquake catalogs by combining all available data from regional, national, and international seismological agencies and reducing magnitudes to a uniform scale. The task of identifying and removing duplicates that arise during the merging process is solved using the authors' modification of the nearest neighbor method. It is evident that the intelligent merging of different earthquake catalogs for the same territory will improve the completeness and representativeness of events in the final integrated catalog. In this article, the earthquake catalog of the western sector of the Arctic zone of the Russian Federation (AZRF) covering the period 1962–2022 was created by merging three regional Russian catalogs and the ISC catalog. The ratio of magnitude types in the catalog for different seismic networks was analyzed, and magnitude estimates were unified based on the obtained ratios. For analyzing seismic activity in the western AZRF, it is recommended to use earthquakes from the period 1998–2020 when the catalog was significantly cleaned from explosions and other events of the "non-earthquake" type. [ABSTRACT FROM AUTHOR]

After a big earthquake, signal-to-noise ratio (SNR) for majority of smaller events is inappropriate. However, once we study frequency-dependent SNR, the opportunity to observe high-frequency content of aftershock series rises. During the week of 2016 November 13–20, more than 400 earthquakes of M4+ has been recorded within radius of 2 degrees [ISC, 2018] by the KHZ accelerometer, of Geonet network [Petersen et al., 2011]. The median interval between origin times is 7 min 51 sec, and about 18% of earthquake recordings intersects. We applied a new procedure of SNR determined considering a big pre-event. At the next step, spectra of those aftershocks which are recoverable at some frequencies, can be studied. To estimate SNR variations during a week, at first, time windows of 60 and 30 min were used (with 50% overlap, band filtering and hanning window were applied). Then, we used several time windows lengths, of 60, 50, 40, 30, 20, and 10 sec, considering the resolution of the Fourier amplitude spectrum and number of wavelengths of 1–0.05 s period in it [Perron et al., 2018]. And two versions of estimating noise level were implied. The first one is a classical approach (noise spectrum of the same length right before the S-wave group, and ratio of 3 is a minimum considered) what removes about 25% of aftershocks out of study. The second approach is normalizing noise level on an averaged one within longer periods, such as 24 and 12 hours, 60 and 30 mins. While averaging the group of max values corresponding to the biggest events were excluded. Using a set of ratios, the decision about appropriateness of SNR was taken. Thus, using of normalized noise spectra allowed recovering of bigger portion of higher frequencies for about 10% of earthquakes, recorded by KHZ (one of the closest stations to the epicenters), during the week of 2016 November 13–20. The study was supported by the grant from the Russian Foundation for Basic Research (project 18-35-00029). [ABSTRACT FROM AUTHOR]

The Commander Islands region, tectonically, is unique, being at the junction of the Pacific plate and Bering plate [Cross, Freymueller, 2008]. The tectonic deformation is distributed in the region between a few sub parallel shear faults, of which the Aleutian transform is the most evident.Another such shear fault, the Bering fault, was activated in 2017, when on its section with the length of 400 km, a shear fracture-source with Mw = 7.8 [Lay et al., 2017] and with the epicenter near the Medny Island, with a displacement of about 2 m, caused a tsunami of a limited scale [Chebrov et al., 2017]. Its sizeable aftershock sequence (more than 150 earthquakes with M > 3.5 in the first two weeks), recorded by the digital seismic network of the Kamchatka Branch of Geophysical Survey, Russian Academy of Sciences.Using about 1000 records of 5 stations equipped by CMG-5TD for earthquakes of 2011-2017 with ML of 3.5–6.5 (aftershock sequence and background seismicity), source spectra of S-waves were recovered, with determining of seismic moment and two corner frequencies [Gusev, 2018].The mass estimates of the first and second corner frequencies were also used to study their scaling properties, b1 equals to 0.35 (with standard deviation of 0.02), and b2 is 0.15 (with standard deviation of 0.03) what is not within assumption of similarity. Moreover, b2 value is less than 0.23 as observed for other earthquakes near Kamchatka peninsula [Skorkina, Gusev, 2017].The study was supported by the grant from the Russian Foundation for Basic Research (project 18-35-00029). [ABSTRACT FROM AUTHOR]