Analysis of seismic efficiency of the electromagnetic pulse source "Yenisei"

<p>We developed a computational technology for numerical modeling of wave fields generated by seismic sources in blocky-layered geological media, and applied it to the analysis of efficiency of the electromagnetic pulse source of new generation "Yenisei", created recently by international geotechnical company "Geotech Seismic Services". To describe wave processes, we worked out new mathematical models of the dynamics of elastic, viscoelastic and elastic-plastic media, of porous and granular materials taking into account the increase in stiffness of such materials as pores collapse, [1]. Algorithms of numerical implementation of governing equations were realized for the cluster-type supercomputers, based on the method of two-cyclic splitting with respect to spatial variables. The conducted computational experiments have demonstrated that the proposed technology allows reproducing the system of waves near the region of excitation of seismic oscillations in 3D setting with a high degree of details and accuracy, [2]. We analysed frequencies and amplitudes of waves generated in the near-surface soils, and showed that our computational results are in a good agreement with seismic parameters of a real electromagnetic pulse source. We studied seismic efficiency of the pulse source as the ratio of the energy passing through the reflecting surface in the depth of layered massif to the energy of pulse effect on the surface. Besides, the energy of surface waves, which is obviously useless for the excitation of reflected waves, was estimated. To compare the energy efficiency of pulse sources with seismic sources of periodic action (vibrators), the problem of cyclic loading through the platform was solved numerically by the same method and the same geometric scheme. The seismic efficiency of vibrator was calculated by the maximum value of the energy fluxes during large time interval. Judging by computations, the pulse seismic sources are not inferior to the sources of vibratory type by seismic efficiency in the range of low frequencies. However, it is necessary to take into account that they differ sharply by the level of expended energy, because the energy of a pulse source, needed for generation of incident wave of a given amplitude, is many times lower than the energy of a vibrator.</p><p>The reported study was supported by the Russian Foundation for Basic Research, Government of Krasnoyarsk Territory, Krasnoyarsk Regional Fund of Science to the research project No. 18-41-242001: "Analysis of wavy seismic fields generated by the electromagnetic pulse source "Yenisei" in heterogeneous soil massifs during geological exploration in the conditions of northern regions of Eastern Siberia".</p><p>References</p><ol><li>Sadovskaya O., Sadovskii V. Mathematical Modeling in Mechanics of Granular Materials. Ser.: Advanced Structured Materials, vol. 21. Springer, Heidelberg – New York – Dordrecht – London, 2012. 390 p.</li> <li>Sadovskii V.M., Sadovskaya O.V., Efimov E.A. Analysis of seismic waves exited in near-surface soils by means of the electromagnetic pulse source "Yenisei". Materials Physics and Mechanics. 2019. V. 42, No. 5. P. 544–557.</li> </ol>

То the synchronous work of pulsed sources of seismic waves

Researches have been made with the use of a hydropneumatic source of seismic waves. This source on the realized efforts of the shock interaction with a soil half-space considerably exceeds all known designs of radiators (sources) of pulse type. In this regard it shows higher seismic efficiency. The most important characteristic of the work of the pulse sources of seismic waves is a stability of the response time — a time interval from the moment of giving of a signal for producing of the blow until the very blow. Only with the achievement of the necessary stability the work in the mode of grouping of sources and accumulation of signals is possible. Features of the formation of response time of a hydropneumatic source are given. The analysis of the assessment of the parameters of synchronism of the pulse sources is made by a modem control system of their work. An influence of the rigidity of the soil on the assessment of stability of the response time and synchronism is shown. The system of the assessment of the stability used in the existing pulse sources at its application does not reflect the actual stability of response time in the radiators possessing a big force of blow.