Active Monitoring With The Use Of Seismic Vibrators: Experimental Systems And The Results Of Works

HR: 08:45h
AN: S31C-04 [Abstracts]
TI: Active Monitoring With The Use Of Seismic Vibrators: Experimental Systems And The Results Of Works
AU: * Kovalevsky, V
EM: kovalevsky@sscc.ru
AF: Institute of Computational Mathematics and Mathematical Geophysics SB RAS, pr.akad.Lavrentieva, 6, Novosibirsk, 630090 Russian Federation
AU: Alekseev, A
EM: alekseev@sscc.ru
AF: Institute of Computational Mathematics and Mathematical Geophysics SB RAS, pr.akad.Lavrentieva, 6, Novosibirsk, 630090 Russian Federation
AU: Glinsky, B
EM: gbm@opg.sscc.ru
AF: Institute of Computational Mathematics and Mathematical Geophysics SB RAS, pr.akad.Lavrentieva, 6, Novosibirsk, 630090 Russian Federation
AU: Khairetdinov, M
EM: marat@opg.sscc.ru
AF: Institute of Computational Mathematics and Mathematical Geophysics SB RAS, pr.akad.Lavrentieva, 6, Novosibirsk, 630090 Russian Federation
AU: Seleznev, V
EM: sel@gs.nsc.ru
AF: Geophysical Survey SB RAS, pr. akad. Koptyuga, 3, Novosibirsk, 630090 Russian Federation
AU: Emanov, A
EM: emanov@gs.nsc.ru
AF: Geophysical Survey SB RAS, pr. akad. Koptyuga, 3, Novosibirsk, 630090 Russian Federation
AU: Soloviev, V
EM: solov@gs.nsc.ru
AF: Geophysical Survey SB RAS, pr. akad. Koptyuga, 3, Novosibirsk, 630090 Russian Federation
AB: Active methods of geophysical monitoring with the use of powerful seismic vibrators play an important role in the investigation of changes in the medium's stressed-deformed state in seismic prone zones for problems of seismic hazard prediction. In the last three decades, this scientific direction has been actively developed at institutes of Siberian Branch of Russian Academy of Sciences. In this period, experimental systems for the active monitoring of the medium, which include powerful vibrational sources with computer control systems, mobile specialized complexes for the precision recording of vibrational seismic signals, and data processing systems have been created. A review of various constructions of resonant vibrational seismic sources with a vibrational force of 100 tons in the frequency range from 5 to 15 Hz and the principles of creation of precision computer control systems and low-frequency three-component recording systems VIRS-M, VIRS-K, and ROSA is presented. A method for the active monitoring of the medium with the use of wideband sweep signals and narrow-band harmonic signals radiated by seismic vibrators has been developed. To determine the sensitivity of the active monitoring system, some experiments to detect the influence of the Earth's crust tidal deformations (of the order of 10-7) on seismic wave velocities have been performed. A 100-ton seismic vibrator and recording systems were located at a distance of 356 km. The radiation sessions of harmonic and sweep signals were repeated every 3 hours during 8 days. This made it possible to construct the time series of variations in the amplitudes and phases of the signals and wave arrival times. Both 12-hour and 24-hour periodicities correlated with the earth's tides were distinguished in the spectrum of variations of the recorded signals. The experiment has shown that the active monitoring system makes it possible to detect relative variations of the seismic wave velocities of the order of 10-5 - 10-6 in an area of 300-400 km around the source. This makes possible the direct monitoring of the state of stresses in an area of 100 thousand km2 to detect the regions and phases of the critical stress as an earthquake precursor. In recent years, works on the use of the method of vibroseismic interferometry for the active monitoring of the lake Baikal region have been started. The method is based on the seismic sounding of the region by powerful seismic vibrators with a long radiation of narrow-band harmonic signals. The changes in the stressed-deformed state are determined through the variations of the amplitude-phase characteristics of stationary wave fields, which are excited in the medium due to a long-time radiation of harmonic signals of constant frequency from the vibrator. The method of vibroseismic interferometry has a high sensitivity to the time changes of the parameters of the medium in the case of long-distance observations. A peculiarity of the experiments is the simultaneous use of the data of regional seismic stations and mobile recording complexes.
DE: 7223 Seismic hazard assessment and prediction
DE: 7294 Instruments and techniques
DE: 7200 SEISMOLOGY
DE: 7205 Continental crust (1242)
SC: Seismology [S]
MN: 2004 AGU Fall Meeting