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The paper presents the studies of the Khuvsgul earthquake on January 11, 2021 at 21:32 UTC (January 12, 2021 at 05:32 local time), MW = 6.7, ML = 6.9, and the seismicity structure in the aftershock period for the Altai-Sayan mountain region and the Baikal rift zone, where the epicenter of this earthquake was located. Two faults are seismically activated, diverging from the southern end of the aftershock area at an acute angle: one in the northeast and one in the northwest direction, as well as transverse faults between them. According to the epicenter position and studies of the source area by other authors, the main event corresponds to the northeastern fault, and large aftershocks occurred at the junction of the northwestern fault with transverse faults feathering from the east. The main event was immediately followed by a series of large aftershocks, the strongest of which occurred on March 31, 2021 with ML = 6.2 and on May 3, 2021 with ML = 6.4. Spatial changes in the seismic regime of the aftershock region led to the predominant activity of its southern end. The junction area of the collisional structures of the Altai–Sayan folded zone and the rift structures of the Baikal depressions system is distinguished in seismicity as a block structure with increased seismicity near the block boundaries. First of all, these are the Tuva-Mongolian block and the eastern part of the Sayano-Tuva block. After the Khuvsgul earthquake of 2021, a block structure with the activation of the epicentral zones of the 1991 Busingol earthquake, the 2011–2012 Tuva earthquakes, and other structures seismically active until 2021 has increased seismic activity. It is proved that the 2014 Khuvsgul earthquake occurred under the basin of the same name and is associated with other faults than the 2021 earthquake and is not a direct precursor of the 2021–2022 activation. [ABSTRACT FROM AUTHOR]

Abstract—The MW = 6.7, ML = 6.9 Khuvsgul (Khubsugul, Khövsgöl) earthquake occurred on January 12, 2021 in the Northern Mongolia close to the border of Russia. The earthquake caused ground shaking which reached intensity IX at the epicenter and was perceptible in the cities and villages of the Eastern and Western Siberia. The earthquake occurred in the region of the same-name fault and caused intense aftershock process on a segment between two fault's bends. The fault segment encompassed by the aftershocks goes from the lake to the northwest. Seismic activation has involved a segment of the boundary of the ancient Tuva–Mongolian microcontinent hosting the parallel Khuvsugul and Darkhat rift depressions and the Busingol rift depression consisting of three linearly elongated troughs. Until the present, the region of the Busingol depression was distinguished by high seismicity, whereas the regions of the Darkhat and Khuvsgul depressions were characterized by moderate and low seismicity, respectively. The earthquake of 2021 is the largest earthquake that occurred on the Khuvsgul fault over the entire history. In less than two months, the level of the frequency–magnitude graph for the aftershocks has exceeded the level of the annual frequency–magnitude graph of the earthquakes for the Altai–Sayan mountain region. The aftershock density is nonuniformly distributed along the fault; the structure of the distribution is correlated to the unilateral block structure of the Earth's crust east of the activated fault segment. The seismic potential of the Khuvsgul fault was estimated at Mmax = 7–7.5, and this earthquake, as suggested by the geological data, is not the maximum possible event. Given that seismic activation after the 1991 Busingol earthquake has not yet ceased, we have two strong activations in the Tuva–Mongolian block which can significantly affect evolution of its seismicity. [ABSTRACT FROM AUTHOR]

The Gorlovsky coal deposit began to be intensively developed in the last decade, and, as a result, technogenic earthquakes started to occur in the area of its quarries. The Kolyvan earthquake with M = 4.3, which occurred on January 9, 2019, was the largest of them and had a tangible impact on settlements including the city of Novosibirsk. This earthquake is the strongest in the area for more than a hundred years, being second to the 1882 Berdsk earthquake. Based on the analysis of seismicity, it is shown that the seismic hazards for Novosibirsk from natural and technogenic seismicity are comparable. The only differences are that zones of natural and technogenic seismicity are spatially remote from each other and catastrophic natural earthquakes will occur less frequently than technogenic ones. [ABSTRACT FROM AUTHOR]