Vibroseismic Observations in Seismically Active Zones of Siberia

High-power vibration sources were developed in Siberian Branch of the Russian Academy of Sciences during 30 years for use in active seismology and studies of Earth's deep structure. Most of data is obtained using eccentric 40- and 100-ton vibrators. Current research involving these sources covers Baikal rift zone, Altay-Sayan folded area and Okhotsk-Chukotski regions in Russia. Using one week to 15-20 days recording intervals, the vibroseismic observations were repeated for several years in the south of Baikal Lake and in Novosibirsk region in the framework of active monitoring technology. The total area of vibroseismic monitoring in the south of Lake Baikal exceeds 20000 km2. Such spatial scale allows to control stress changes in the zones of large faults (Obruchevski, Primorski, Bolsherechenski), which repeatedly activate during rift genesis. Near Novosibirsk, the system of vibroseismic monitoring is focused on changes of the Earth crust physical characteristics caused by seasonal changes of water levels in Novosibirsk reservoir. It is oriented transversely and along the spread of reservoir at 50-70 km distances from the source location. Variations of elastic waves correlate with process of earthquake preparation in 2002 and were detected in the south of Lake Baikal. Results of long-term experiment near Novosibirsk suggest that the observed 0.3-0.6% variations in velocities of longitudinal and shear waves are connected with seasonal changes of water levels (up to 5m) in the biggest reservoir. Overall results suggest possibility of vibroseismic monitoring with small number of high-power vibrators and a large number of recording stations.