Features of excitation, registration and estimation weak seismic signals at minimization explosive technology

The report is devoted to features of excitation and registration of weak signals, an estimation of<br>changes of amplitudes of signals in common units of value (mV) from the moment of their submission on an<br>input of recording system before formation of a final time section. Results of works JSC “Zappricaspigeophizica”<br>are put in a basis of the report for the period with 1990 on 2002.<br>Deal with a problem of small charges, JSC “Zappricaspigeophizica” in a mode of preliminary<br>tests used at industrial works charges in weight 10, 20, 30, 50, 75, 100, 200 g and at the decision of geological<br>tasks in all cases it is received high resolution data (fig. 1).<br>At small charges the amplitude of registered signals will decrease concerning amplitude at standard<br>charges, but in all cases of value of amplitude of a signal a scale of record of seismic stations do not fall outside<br>the limits. As a rule, weak signals are submitted to more high frequency component and at small charges<br>seismic prospecting due to expansion of a spectrum from average frequency passes in high resolution<br>seismic prospecting . The big charges are not combined at all with modern ways of registration and processing.<br>In the report the list of small charges, their characteristics, merits and demerits is resulted. On the<br>basis of the theory of the spherical center developed by Gurvich I.I., attempt graphically is made to esti<br>mate connection of quantity of energy which is spent for formation of seismic waves with weight of a charge<br>(fig.2).<br>On field records for different charges the level of seismic signals registered in an interval t=0,3-2,7<br>sec carried out to an input of station which correspond with a scale of record of a seismic station is estimated,<br>in view of own noise of station and receiver line noise (fig. 3). The specified comparisons show, that at<br>explosive small and big charges on an input of a 24-digit seismic station the signal which is registered on all<br>ranges of amplification without distortions, practically in the middle of a scale of record moves.<br>Most interest is works in the walley of Talymu River in northern part of Takla-Makan desire (China),<br>because target horizons in this area locate dipper then 3,5 km and reflections from this horizons are located<br>on the seismic section on time from 3 to 5 sec. (fig.4) Testing of HRS in northern part of Takla-Makan desire<br>is interest because it demonstrate the possibility of registration of high frequency part of specter signal<br>amplitude in band of 60-130 Hz. In the same time, this amplitude is higher than amplitude of the same part<br>of signal, obtained by charge with 6 kg weight.<br>The questions of application of small charges stated in the report, measurement of levels of signals<br>in mV, an estimation of efficiency of processing on the basis of gauging amplitudes of voltage of electric<br>fluctuations allow to speak about opportunities of other approaches at calculations of seismic techniques for<br>various geological conditions.