ИСТИНА

We continued our study on the Big Udina volcano in Kamchatka area. It is situated to the south of active Plosky Tolbachik volcano and in October 2017 active seismicity was registered in its vicinity. We analyzed evolution of seismic activity and surface displacements using ALOS-2 and Sentinel-1A images. We showed that to the contrary of previous hypothesis that this activity is caused by magma uplift to the shallow volcanic chamber, the real process is magma down-welling to the depth hence risk of new eruption is low [1]. ALOS-1 images were also used together with Sentinel-1A images to investigate subsidence of the lava field formed during Tolbachik fissure eruption of 2012-2013. The maximum average displacement rates for the snowless periods of 2017 -2019 were 285, 249, and 261 mm/year, respectively. The maximum subsidence was registered in the areas with the maximum lava thickness on the Leningradsky and Toludsky lava flows. The estimated the thermal subsidence of the lava surface during its cooling is generally close to the SAR values over a significant part of the lava field, but in the upper parts of the lava flow, the SAR subsidence values are several times higher. We associate this subsidence with lava tubes [2]. Now we are working on more detailed thermal problem to better fit SAR data. ALOS-1 images were used to estimate displacements of the slopes of the Koryaksy volcano in result of its last activation in 2008-2009 which was accompanied by intense fumarole and seismic activity. The important question for people living in its vicinity, in Petropavlovsk-Kamchatka city, is: Was the eruption associated with the rise of magma under the volcanic edifice or was it caused by fracturing of the basement rocks of the volcano and penetration of groundwater into the high temperature zone? SAR LOS displacements reached 25 cm and cannot be explained by the formation of a layer of ash deposits or slope processes. The most probable explanation for the displacements is the intrusion of magmatic material into the edifice of the volcano forming of a dike. Dike parameters were estimated as follows: lower edge depth of 0.5 km above SL, dimensions along the strike and dip of 1.0 and 2.4 km, dip angle of 45 to 60°. Consequently, the processes occurring under the volcano can create a danger for the settlements and infrastructure facilities located in its vicinity and require continuous monitoring [3].