Measurement of Earth electric potentials and ULF signals for seeking earthquake precursors

Measurements of the Earth electric potential (EEP) and electromagnetic field complement existing facilities for studying various kinds of geodynamical formation and phenomena. An apparatus for electrotelluric field measurements in the ULF range is suggested. This apparatus constitutes a system for multipoint measurements. Such measurements appear to be a principal element of programmes toward seeking electromagnetic precursors of earthquakes. First results on anomalous electrotelluric signals prior to great earthquakes are illustrated.