An analysis of local seismicity within the Avacha–Koryakskii Volcanic Cluster during the 2000–2016 period revealed a sequence of plane-oriented earthquake clusters that we interpret as a process of dike and sill emplacement. The highest magmatic activity occurred in timing with the 2008–2009 steam–gas eruption of Koryakskii Volcano, with magma injection moving afterwards into the cone of Avacha Volcano (2010–2016). The geometry of the magma bodies reflects the NF geomechanical conditions (tension and normal faults, Sv >SHmax >Shmin ) at the basement of Koryakskii Volcano dominated by vertical stresses Sv, with the maximum horizontal stress SHmax pointing north. A CFRAC simulation of magma injection into a fissure under conditions that are typical of those in the basement of Koryakskii Volcano (the angle of dip is 60о, the size is 2 × 2 km2, and the depth is –4 km abs.) showed that when the magma discharge is maintained at the level of 20000 kg/s during 24 hours the fissure separation increases to reach 0.3 m and the magma injection is accompanied by shear movements that occur at a rate as high as 2 × 10–3 m/s, thus corresponding to the conditions of local seismic events with Mw below 4.5. We are thus able to conclude that the use of planeoriented clusters of earthquakes for identification of magma emplacement events is a physically sound procedure. The August 2, 2011 seismicity increase in the area of the Izotovskii hot spring (7 km from the summit of Koryakskii Volcano), which is interpreted as the emplacement of a dike, has been confirmed by an increase in the spring temperature by 10–12°С during the period from October 2011 to July 2012.

A conceptual model of the thermal and water recharge of the Ketkinsky geothermal field as a product of magma and water injection from the Koryaksky volcano located 24 km apart was proposed. A digital hydrogeological model of the Ketkinsky geothermal field was developed in the volume of 7 km x 5 km x 2.5 km (from the topographic surface), it includes the space drilled by exploration and production wells. The model is based on an analysis of 3D distributions of temperature, pressure, salinity and CH4 content, geometrization of productive faults and well productivity characteristics. The geofiltration space was zoned in the model with separation of
deep and shallow productive geothermal reservoirs, the area of deep thermal fluid upflow in the SSE part of the model base and the area of hidden thermal water discharge at the ground surface.
A natural state inversion iTOUGH2-EWASG simulation was performed to estimate the deep thermal water upflow and permeability of productive geothermal reservoirs. The deep thermal water upflow is estimated to be about 10 kg/s, the permeability is estimated to be 190 mD (shallow productive reservoir) and 35 mD (deep productive reservoir). Inverse iTOUGH2-EWASG modeling of the hydrodynamic operating history of 1989–2020 was used to estimate the compressibility of the productive geothermal reservoirs: the compressibility of the deep reservoir is estimated at 7.16E-10 Pa???? 1, the shallow reservoir at 4.14E-07 Pa???? 1. Direct iTOUGH2-EWASG modeling with the above parameters reproduces the history of salinity and temperature changes in production wells.
Forecast modeling of existing producing wells #23, K6, K01, K5 operation for 25 years with application of submersible pumps at immersion depth of 70 m confirms the possibility of their sustainable operation with total flow rate not less than 14.2 kg/s, adding four producing wells may yield to 54.3 kg/s with retaining of produced water quality (temperature, gas content of CH4, salinity).
The use of submersible pumps and reinjection can significantly increase the reserves of Ketkinsky field to 165–175 kg/s of 70–80 ◦C and 60–70 g/s of CH4. Additional increase in reserves may be obtained by drilling the already known thermal anomaly in the SSE sector of the field and in the SWW foothills of Koryaksky volcano.

Abstract—We discuss the water!level variations in the E!1 well for the time period between May 2006 and
2010, inclusive. A trend towards an increasing level at an abnormally high rate occurred from mid!2006 to
December 2009. This increase is regarded as the response of the aquifer of gas!saturated ground water that
exists in the volcanogenic–sedimentary deposits of the Avacha volcano!tectonic depression to volumetric
strain changes during the precursory period and the occurrence of a swarm of small earthquakes ( = 8.3)
in the area of Koryakskii Volcano and to its phreatic eruption. We estimated the volumetric compression as
Δε = –(4.1 × 10–6–1.5 × 10–5) from the amplitude of water!level rise using the elastic parameters of the wa!
ter!saturated rocks. While the strain source was active, we observed a decreasing sensitivity of the hydrologic
regime in the well to the precursory processes before large (M ≥ 5.0) tectonic earthquakes.

Avacha group includes two active and potentially dangerous volcanoes, Avachinsky and Koryaksky, located close to Petropavlovsk-Kamchatsky, the main city of Kamchatka. We present the results of two independent seismic studies of shallow crustal structures beneath the Avacha group based on passive and active source observations. The first study is based on the analysis of continuous recording by 11 seismic stations installed over the Avacha group in 2012 and 7 permanent stations in the same region. We present a series of 2D Rayleigh-wave group velocity maps based on correlation of ambient noise, that were then converted into 3D distribution of shear wave velocity. The second work was based on the reprocessing of an active source deep seismic sounding profile across the Avachinsky volcano that was shot in 1982–1984. We made the analysis of travel times of refracted waves using a 2D tomography inversion. The resulting seismic models appear to be consistent with each other and show clear low-velocity zone to the SW of the Avachinsky volcano and high velocity structures to NE. These observations also agree with the existing gravity and magnetotelluric measurements. Based on the obtained seismic models we identify two large buried calderas and large lava flows that are thought to be related to a series of large eruption episodes of Avachinsky occurred within the last 30,000 years.

Abstract-This study is the first to show, using data from the eruption of Koryakskii Volcano, Kamchatka that began in December 2008 and continued through 2009 that the water in permanent and temporary streams that start on the slopes of the volcanic cone and in temporary lakes when contaminated with fresh tephra is a specific hazard factor related to long-continued hydrothemial-phreatic eruptions on that volcano. This water is characterized by increased acidity (pH 4.1-4.35) and large amounts (up to 50-100 cm /liter) of solid suspension and is unfit for drinking and irrigation. When combined with tephra, it probably produced mass destruction of a number of animals who lived on the slopes and at the base of the volcano. The water contaminated with tephra is an important component of the atmospheric mud tlows occurring on Koryakskii Volcano; for several future years it will be a potential source for enhancing the acidity of ground water in the volcanic edifice.

Remnants of five catastrophic lahars have been discovered, described, and dated by the carbon-14 method. They occurred during eruptions of Avacha (violent explosions with voluminous juvenile pyroclastics) and Koryakskiy (large fissure lava flows): 3500 to 3200 14C years ago or 1900-1500 years B.C. These lahars were much higher in vigor, hazard, and effect on the environment than the lahars generated by the historic eruptions of these volcanoes. -from Journal summary

In the present National Report, major results are given of research conducted by Russian scientists in 2011–2014 on the topics of the International Association of Volcanology and Chemistry of the Earth’s Interior (IAVCEI) of the International Union of Geodesy and Geophysics. Kamchatka Peninsula with its famous Klyuchevskaya Group of volcanoes is the most volcanically active area in Russia and one of the most active in the world. Majority of researches and scientific results on Volcanology and Geochemistry of the Earth’s Interior during 2011–2014 were achieved in this region including recent data on new Tolbachik fissure eruption in 2012–2013. Besides it, the scientific results on the magmatism outside Russia, which were achieved by Russian scientists, are also included in this review. Major achievements in the chemistry of the Earth, geothermy, geodynamics, geochronology and deep mantle structure are featured. The studies as for the single volcanoes as well the regional observations are outlined. The theoretical and applied efforts connected to the volcanological processes are considered. The main conclusions are illustrated by summarized figures. All the required references are given.