A physical model is proposed for the possible effect of telluric currents on macrofracturing in the Earth's crust and the triggering of earthquakes via the interaction of telluric currents with the geomagnetic field. For implementation of the considered processes, a an escalated regime due to positive feedback between the decrease in electrical conductivity of the developing earthquake source and the increases in current and pressure in this source was established. Estimates of characteristic earthquake triggering time that agree with the experimental data were obtained. The model explains the interrelationship between some observed elec tromagnetic phenomena and earthquake development processes in seismoactive zones.