Application of underground electric antennas in the stress-stain state monitoring system of geological environment

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   Since 2003 electromagnetic measurements with underground electric antenna
   together with borehole geoacoustic and other measurements have been
   carried out in Petropavlovsk-Kamchatskii geodynamical experimental field
   since 2003. By March 2013, the measurement network consisted of four
   telemetry points, based upon the boreholes G-1, R-2, E-1, K-33, and the
   Center for data acquisition and processing, which is located in the
   building of IVS FEB RAS. The measurements are focused on the tasks of
   monitoring of the stress-strain state of geoenvironment and prediction of
   seismic hazard. Currently, underground vertical electric antennas have
   been used in three different designs. Selection of antenna type is
   determined by the peculiarities associated with borehole location (such as
   urban area, forest etc.), electromagnetic radiation level and borehole
   construction. Within the tasks, electromagnetic measurements are used in
   several applications, in particular, to estimate the electrical
   conductivity changes of rocks surrounding the borehole. The principle of
   such estimations is provided by the application of underground antennas,
   where the bare from geoenvironment borehole casing pipe is used as the
   basic element. These results suggest high sensitivity of the developed
   monitoring method for the rock electrical conductivity changes and the
   consistency of the obtained results with the data of other measurements.