Monitoring crustal deformations in the Northern Caucasus using a high precision long base laser strainmeter and the GPS/GLONASS network

The results of long-term monitoring of crustal deformations in the Northern Caucasus using a high precision long base laser strainmeter and the GPS/GLONASS network are presented. The Baksan laser interferometer-strainmeter with a measuring arm length of 75 m and resolution of 2.3×10−13 is mounted inside an underground gallery in a mountainous area near to the dormant volcano Elbrus. An analysis of crustal strains recorded by the Baksan laser interferometer revealed the shallow magmatic chamber in the structure of Elbrus Volcano. The analysis is based on estimation of parameters of the resonant modes of magmatic structures excited by powerful teleseismic signals. We estimated the depth and dimensions of the magma chamber, as well as the properties of the magma fluid which are corroborated by available geological and geophysical evidence. The harmonic analysis of tidal strains, performed with the help of the ETERNA software package, is defined that amplitude factors of the main diurnal and semidiurnal waves appear to have been underestimated. The observed anomaly of the M2 wave (12%) is shown to be due to the influence of the main magma-controlling fault associated with the deep magma source of the Elbrus Volcano. The GPS observations in the Nortern Caucasus area began in 1993 as a part of the SELF project. Currently, four stationary GPS/GLONASS stations located in this area form the base of the regional Northern Caucasus Deformation Array (NCDA). Based on the results of first observations we find constraints on the velocity field and uplift of the Nortern Caucasus. The modern motion of the Northern Caucasus is characterised by the velocity value of 28 mm/year and is mainly defined by the general tectonic movement of the Eurasian plate in the northeast direction in the ITRF.