Geo-electromagnetic monitoring of seismotectonic processes in Transcarpatian seismically active zone

Since 1970 geomagnetic investigations are carried out in the seismically active area of Transcarpathia to study
modern geodynamics of the Earth crust. The region is characterized by moderate seismic activity. Maximum
intensity of earthquakes here does not exceed 7-8 according to MSK-64 scale, epicenter depths is up to 10 km.
To study earthquake precursors in the area of Carpathian geodynamic polygon we have continuous measure-
ments of geomagnetic field F (4 stations), and also magnetic variation measurements of the geomagnetic field
components (2 stations) at permanent geomagnetic stations since the 90-th. The following basic results were
received.
According to the continuous regime measurements we got time changes of the local magnetic field – tectonic-
magnetic anomalies of various duration and origin, namely: long period (several years) changes of differential
field F of the tectonic origin associated with seismically calm periods diring a gradual accumulation of pressure
at regional level, the episodically changes of differential field F, which are possibly caused by preparation of
some seismic events in the region, and seasonal anomalous changes of differential field F which are the result of
quasi periodic changes of meteorological parameters. The amplitude of the tectonic-magnetic anomalies does
not exceed 3 nT.
Except the classical bay-like precursor anomalies with the duration from several days to several months we
detected various types of anomalies: sharp changes of the field level; quasi-linear trends and dispersion increase
of differential field Т 5-15 days before earthquakes.
Till 1999 magnetic variation observations were carried out by the V.Bobrov analogue stations, since 1999 –
by digital stations LEMI -008 to study time changes of induction vector. Weise vectors are calculated from the
digital МVS data (discreteness is 1 meas/sec) for the periods: to 2,5 min, 2,5-5,0 min, 5-10 min, 10-20 min,
20-40 min, 40-60 min. In time series seasonal and diurnal variations are distinguished. Time-spatial correlation
of the anomalous variations of induction vectors with the nearest (up to 30 km) earthquakes was determined.
Complex of geomagnetic and magnetic variation methods makes the investigation of seismic propagation
more informative and the revealing of earthquake precursors more reliable.