[1] Russian Acad Sci, Geol Geophys & Mineral Joint Inst, Inst Geophys, Novosibirsk, Russia
[2] Russian Acad Sci, Inst Automat & Electrometry, Novosibirsk 630090, Russia
[3] Observ Royal Belgique, B-1180 Brussels, Belgium
[4] Baikal Expt Method Seismol Expedit, Irkutsk, Russia