Sergey L. Senyukov

February 2, 2025 marked the 25th anniversary since the start of the Monitoring of Volcanic Activity project conducted by the Kamchatka Branch (KB) of the Geophysical Survey (GS) of the Russian Academy of Sciences (RAS). At present time the studies are being conducted in near real time in four directions: (1) seismicity monitoring, (2) visual and video observations, (3) satellite-based monitoring, and (4) infrasound control. The daily work conducted by the Kamchatka Branch to acquire, to process, and to present the information on volcanic activity enables timely and reasonable assessment of the state of volcanoes, yielding conclusions as to possible developments of volcanic activity. The monitoring results are daily published in the factual database “Activity of Kamchatka Volcanoes”. The original variant of the database using pages in the html format did not envisage full-scale research using the stored observation and processing results; for this reason a new database was developed in 2014 for the Eruptions of Volcanoes in Kamchatka and on the Kuril Islands system, in addition to a package of program modules for data processing. The observation and processing results systematized for the 25 years of this work provided for and helped achieve successes in dealing with problems arising in short-term prediction of strong paroxysmal eruptions on Bezymianny, Klyuchevskoi, and Kizimen volcanoes. For the case of such rarely erupting volcanoes as, e.g., Koryaksky, Avachinsky, Mutnovsky, Gorely, Plosky Tolbachik, and Kambalny, the work involved recording and systematizing seismic and other geophysical data, which will contribute to a better assessment of their volcanic hazard in the future.

This article presents data on the MW 8.9 Kamchatka earthquake of July 29, 2025, compiled by the Kamchatka Branch of the Geophysical Survey of the Russian Academy of Sciences (KB GS RAS) as of December 31, 2025. The Kamchatka earthquake is one of the largest seismic events in the history of instrumental observations. To date it ranks as the sixth most powerful event ever recorded in the world. The rupture zone, estimated based on the aftershock area, is 580 × 180 km and roughly coincides with the source area of the Great Kamchatka Earthquake of November 4, 1952 (MW 9.0). The 73-year gap between these two megathrust earthquakes that occurred approximately in the same area is significantly shorter than what would be expected from the widely accepted concepts of the seismic cycle. The article provides information on source parameters of the main shock, the operation of the Tsunami Warning Service, a catalog of aftershock mechanisms, the characteristics of strong ground motions caused by the main shock, and a brief description of the manifestation of a tsunami. A preliminary assessment of the macroseismic impact of the Kamchatka earthquake and its aftershocks revealed that the earthquake caused shaking of intensity 7–8 on the SIS-17 scale in Severo-Kurilsk and 6–7 in Petropavlovsk-Kamchatsky; no human casualties or serious damage caused by the earthquake and tsunami were recorded throughout the entire area of their propagation. Features of the source process development revealed by the results of the analysis of the diurnal variation of seismic energy released after the main event are discussed. The finite fault slip model of the earthquake based on the coseismic displacements from GNSS observations is presented.

Monitoring of the activity of Kamchatka volcanoes in near real time is carried out since 2000. Con­tinuous monitoring was carried out using three remote methods: 1) seismic monitoring according to automatic seismic stations; 2) visual and video observation; 3) satellite observation of the thermal anomalies and the ash clouds. The monitoring results are posted daily of the website of the Kamchatka Branch of the Geophysical Sur­vey of the Russian Academy of Sciences (KB GS RAS). Klyuchevskoy volcano is the most active and powerful basalt volcano in the Kuril-Kamchatka volcanic region. 11 summit eruptions were recorded on Klyuchevskoy volcano in 2000–2023. Two eruptions from 11 ended in paroxysmal phases and one with a lateral eruption. As a result of the research, seismological precursors were identified with an assessment of their quantitative parameters based on data from local earthquakes and volcanic tremor to predict lateral and summit paroxysmal eruptions. Both paroxysmal eruptions were successfully predicted with a lead time of 5 days. According to the forecast of a paroxysmal eruption in 2023, the Ministry of Emergency Situations of the Kamchatka Territory promptly warned the population of nearby settlements and responsible services about the possible danger.

As part of the international collaboration of several research groups from Russia, France, and Germany, 77 temporary seismic stations were installed in the summer of 2015 for one-year period to conduct a detailed study of the deep structure of the Earth’s crust and upper mantle in the region of the Klyuchevskoi Volcano Group (KGV) in the Kamchatka Peninsula. One of the results of the KISS experiment (Klyuchevskoi Investigation – Seismic Structure of an extraordinary volcanic system) was the final catalog of the joint data from the temporary stations and the permanent network of the Kamchatka Branch of the Geophysical Survey of the Russian Academy of Sciences (KB GS RAS). The catalog comprises 2136 events, including 560 for which the permanent network catalog lacked sufficient data for correct processing. The catalog in .xlsx format and the station bulletin in .isf format are presented in the supplementary material to the paper. A comparative analysis was conducted on the joint solutions of two catalogs: one obtained solely from the data of the KB GS RAS permanent network stations and another from a denser seismic network integrated with KISS stations.

—As part of the international collaboration of several research groups from Russia, France, and Germany, 77 temporary seismic stations were installed in the summer of 2015 for one-year period to conduct a detailed study of the deep structure of the Earth’s crust and upper mantle in the region of the Klyuchevskoi Volcano Group (KVG), Kamchatka Peninsula. One of the results of the KISS experiment (Klyuchevskoi Investigation –Seismic Structure of an extraordinary volcanic system) was the final catalog based on the joint data from the temporary stations and the permanent network of the Kamchatka Branch of the Geophysical Survey of the Russian Academy of Sciences (KB GS RAS). The catalog comprises 2136 events, including 560 for which the permanent network catalog lacked sufficient data for correct processing. The catalog in .xlsx format and the station bulletin in .isf format are presented in the supplementary material to the paper. A comparative analysis is performed of joint solutions of two catalogs, one obtained solely from the data of the KB GS RAS permanent network stations and another from a denser seismic network integrated with KISS stations.

This paper reports the results of seismic, electromagnetic, and gravity surveys, as well as seismicity data in the lithosphere at depth for the active volcanoes in the Avacha–Koryaksky group which is part of the East Kamchatka volcanic belt. We have developed an integrated geophysical model for the crust and lithospheric mantle in the area of study. The resulting distribution of crustal geophysical inhomogeneities, in particular, beneath Avacha Volcano, was used to study the main features of intracrustal fluid saturation and of pathways as channels for deeper fluids to rise to the upper crust. The integrated model assumes that the stresses that arise at boundaries of zones with different conditions of defluidization constitute one of the factors to produce seismicity beneath the active volcanoes. We also incorporate data from regional seismic tomography to deal with a general scheme for deep processes in the lithosphere and the system that supplies magma to the volcanoes. It is assumed that active volcanoes, in particular, Avacha, are connected to the asthenospheric layer of the lithosphere mantle at a depth of about 70–120 km, whence fluids/melts are coming into the magma chamber in the lower crust with subsequent formation of a peripheral chamber in the upper crust beneath the volcanic cone due to the heat supplied by the lower crustal source.

The article presents the results of our gravimetric, seismic and electromagnetic research, as well as the data on deep seismicity of the lithosphere in the area of the active Avachinsky and Koryaksky group of volcanoes, which is the part of the East Kamchatka volcanic belt. We managed to develop the comprehensive geophysical model of the Earth’s crust and lithospheric mantle of this area. Based on the distribution scheme of the Earth’s crust geophysical inhomogeneities in general, and particularly beneath Avachinsky Volcano, we revealed specific features for both intracrustal fluid saturation and conduits through which deep fluids rise to the upper part of the crust. According to the comprehensive model, stresses arising at the margins of zones with different defluidisation conditions, in particular, in the lower part of the crust, and characterizing by contrasting electrical conductivity values, are one of the most important reasons for active seismicity beneath active volcanoes. The general scheme of the deep lithospheric processes and the volcanoes magma feeding system specific features are based on the obtained results and the data on the local seismic tomography. It is assumed that Avachinsky Volcano, being a part of the active Avachinsky and Koryaksky group of volcanoes, is connected with the asthenospheric layer at a depth of ~70–120 km, from which fluid/melts enter into the magma chamber located in the lower crust and then, under the influence of the heat from the lower crustal source, the peripheral chamber is formed in the upper crust beneath the volcano’s cone.

The increase in number and intensity of earthquakes during a pre-eruptive crisis is the main basis of seismic volcano monitoring. However, a strong understanding of how these seismic signals relate to magmatic processes in the magma plumbing systems prior to volcanic eruptions is crucial for these efforts. Here we compare the characteristics of a seismo-volcanic crisis prior to the 2010–2013 explosive-extrusive eruption of Kizimen volcano, Kamchatka with the timescales of processes in the magma plumbing system. These timescales are inferred from the numerical modelling of iron-magnesium intracrystalline interdiffusion in 88 zoned orthopyroxene crystals from dacites and silica-rich andesites collected after the eruption. We find that the eruptible magmas were assembled rapidly during a magma mixing process beginning around 1.5 years before the eruption, which is well correlated with the onset of the seismic crisis. We conclude that the observed seismic re-activation marked the onset of magma mixing and led to destabilization of the reservoir, followed by the eruption.

The increase of number and intensity of earthquakes during a pre-eruptive crisis is the main basis of seismic volcano monitoring. However, the exact relationship between the seismic activity and the volcano-magmatic processes remains unclear. Here we present a direct comparison between characteristics of a seismo-volcanic crisis recorded prior to the 2010-2013 eruption of Kizimen volcano (Kamchatka, Russia) and the timescales of processes in the magma plumbing system. These timescales are inferred from the modelling of Fe-Mg intracrystalline interdiffusion in 88 zoned orthopyroxene crystals from dacites and silica-rich andesites samples collected after the eruption. We show that the eruptible magmas were assembled rapidly during a magma mixing episode ~1.5 years before the eruption, which is well correlated with the onset of a seismic crisis. We conclude that the observed seismic re-activation marks the onset of magma mixing leading to destabilization of the reservoir followed by the eruption after ~1.5 years.

The results of near real-time monitoring of the active Kamchatka volcanoes are described. Continuous monitoring was carried out using three remote methods: 1) seismic monitoring according to automatic telemetric seismic stations; 2) visual and video observation; 3) satellite observation of the thermal anomalies and the ash clouds. Annual results of seismic activity of the Northern (Shiveluch, Kluchevskoy, Bezymianny, Krestovsky, and Ushkovsky), the Avacha (Avachinsky, and Koryaksky), the Mutnovsky-Gorely volcano groups and the Kizimen volcano are presented. 5464 earthquakes with КS=1.8–8.1 were located for the Northern volcano group, 302 earthquakes with КS=1.7–5.7 – for the Avacha volcano group, 295 earthquakes with КS=2.1–6.8 for the Mutnovsky-Gorely volcano group, 462 earthquakes with КS=2.2–8.3 for Kizimen volcano, and 165 earthquakes with КS=2.5–8.4 for Zhupanovsky volcano in 2015. Maps of epicenters, quantities of seismic energy and earthquake distribution by energy classes are given. All periods of activity were fixed and investigated by remote methods in 2015: intensive volcanic activity of the Sheveluch volcano associated with a new cone; the summit explosive-effusive eruption of the Kluchevskoy volcano in January–April; and a continuation of seismic and volcanic activity of the Zhupanovsky volcano after 56-year quite period.