Peculiarities of ULF electromagnetic disturbances before strong earthquakes in seismic active zone of Kamchatka peninsula

Regular observations of ULF electromagnetic disturbances and acoustic emissions at st. Karymshino in seismic active zone of Kamchatka peninsula were carried out during 2001-2003 years. Five seismic active periods with strong earthquakes (M>5) were displayed during this period. These EQs occurred at the Pacific at 20-60 km depth at 100-140 km distances to the East from the st. Karymshino. Analysis of normalized dynamic power spectra of data of high-sensitive (0.2 pT/sqrt(Hz)) three-component induction magnetometer achieved a significant disorder of daily variation and increasing of the magnetic disturbance intensities (from 0.2 to ~1 pT) in the whole investigated frequency range (0.2-5 Hz). The anomaly intensity increasing was observed during the 12-18 hours before main seismic shocks. Maximum of the increasing occurred during 4-6 hours before the EQs. An increasing of acoustic emissions (F=30 Hz) was observed during the same period. A sharp decreasing of the magnetic disturbance intensities was observed 2-4 hours before the EQs. We suppose that physical processes in a hearth of forthcoming EQ lead to an irreversible avalanche-like formation of cracks and stimulation of the acoustic and ULF electromagnetic disturbances.