Vulkanologiâ i sejsmologiâ

The synthetic earthquake catalog for the Eastern sector of the Arctic zone of the Russian Federation is constructed in the paper. It reproduces and models the key properties of the catalog of actual earthquakes in the region. At the regional level, the Gutenberg–Richter magnitude frequency law for earthquakes of different magnitudes is satisfied both for the catalog as a whole and for the catalog of main shocks, in which aftershocks are removed. Local values of the parameters of this law are reproduced. The synthetic catalog includes aftershocks, while local ratios of the number of aftershocks and the total number of earthquakes, estimated from the catalog of actual events, are observed. The results of strong earthquake-prone areas recognition using the FCAZ method are used as a model of the spatial distribution of the strongest earthquakes in the region (М ≥ 5.5). Preliminary calculations of the normative intensity were carried out to compare three variants of the synthetic catalog (full model, without aftershocks, without FCAZ recognition results and aftershocks).

The paper considers the water balance of cold and hot crater lakes of the Vernadsky ridge on Paramushir Island. Precipitation was measured at the height of the craters to calculate the incoming part. A necessary condition for the existence of permanent cold crater lakes with precipitation of ~ 4660 mm per hydrological year is a catchment area of more than 60 thousand m². The evolution of lakes in the craters of the active Ebeko volcano is presented. The volcanic contribution (inflow of water and/or steam of volcanic origin) to thermal lakes in previous periods of time and in the current state of the volcano has been estimated. In the long term, the Middle Crater and the Korbut crater are suitable for the formation of hot lakes. Until the end of the current eruption in the Korbut crater, the formation of a lake in it is impossible. In the post-eruptive period, with an estimated crater diameter of 250 ± 50 m, a volcanic inflow of 8–13 kg/s will be sufficient for the equilibrium existence of a lake with a temperature of 35°C and a mirror area of 25 thousand m². Volcanic steam has been entering the lake in the Middle Crater since 2017, but the lake remains cold. The volcanic inflow should be 5 ± 2 kg/s in order to achieve a balance equilibrium for a lake with a temperature of 35°C and a mirror area of 25 thousand m².

The article discusses the prospects of a new earthquake forecast algorithm based on a set of precursor anomalies previously identified in details as a result of constructing and analyzing a generalized vicinity of a strong earthquake. The difference in physical mechanisms of different depth earthquakes is taken into account. The question is considered, how often typical averaged anomalies can be statistically reliably identified in the foreshock areas of individual strong earthquakes; the regional catalog of Kamchatka and Northern Kuril Islands of the Kamchatka Branch of the Geophysical Surveys of the Russian Academy of Sciences is used. In this catalog, at least one typical anomaly is detected in one third of cases of the target earthquakes with magnitude M ≥ 6.5. The probability of such successful retrospective forecast depends to a decisive extent on the number of events registered in the foreshock zone of a given strong earthquake. This result is supported by the results of the analysis of the world ISC-GEM and GCMT catalogs and the 2023 Turkish Earthquake Doublet. The possibilities for the development of the used forecast method are discussed; attention is drawn to the problem of false alarms.

A review of work on the search for earthquake precursors during the period of detailed seismological observations in the Kamchatka Peninsula in 1962–2022 is presented in comparison with the cumulative graph of seismic energy release and the most powerful earthquakes. A feature of the observation network for earthquake precursors is the location of most “non-seismological” types of observations in a small area of the Petropavlovsk-Kamchatsky test site (PKTS). Analysis of the 14 types of seismic, geophysical and geochemical precursors before seven 2005–2022 shallow and intermediate earthquakes with М_W = 6.6–7.7 showed an increase in the number of precursors N with an increase in the parameter M_W / lgd_h (d_h is the hypocentral distance to the center of PKTS in km), which characterizes the relative intensity of earthquake preparation in the PKTS area. Such a relationship between N and M_W/lgd_h traced for interplate (subduction) earthquakes in the Kamchatka fragment of the Kuril-Kamchatka Island arc as well as consistent with the manifestations of precursors in 1987–2004 and reflects the integrated manifestation of precursors before earthquakes that are the strongest and closest to the PKTS territory. Before such events, the effect of integrated manifestation of precursors (EIMP) was observed in no less than 80% of the precursors of all considered in this work. For such earthquakes, the ratio between the hypocentral distance d_h and the size of the earthquake source L (km) is d_h / L = 3.8–1.6, i.e., the manifestation of EIMP is characteristic of the near and middle (intermediate) zone of the future earthquake. Using the example of four separate types of precursors, it is shown that their threshold values d_h / L = 5.0–8.5 for events with М_W ≥ 6.6. If, during seismic forecasting, the EIMP is diagnosed in real time, then using the threshold value d_h / L ≤ 3.8 set for it, it is possible to significantly reduce the estimate of the distance of a future strong earthquake from the PKTS area and the Petropavlovsk-Yelizovo urban agglomeration, compared with the use of data on individual types of precursors.