卷 55, 编号 1 (2019)

The paper describes a modified apparatus for physically modeling the electroseismic effect of the first kind in rocks. The apparatus makes it possible to simulate the effect when a rock sample is exposed to an electric field with and without current in the sample. Two methods can be used for measuring changes in the acoustic field propagation velocity. The first method excites a pulsed acoustic field and measures the time it takes for the field to propagate from the source to the receiver; the second measures the phase modulation of a sinusoidal acoustic field when the sample is exposed to an electric field. The first method has two modifications: in the first, only an electric field without an active current component is generated in a sample; in the second, both an electric field and an active current component are generated. The apparatus includes a signal generator that excites coherent electric and acoustic fields in rock samples. Field coherence makes it possible to apply an interference-immune phase method for measuring the velocity of a sinusoidal acoustic field and to decrease the sensitivity threshold for a change in velocity from 0.2 to 0.02%. The authors present results of modeling the effect using saltwater-saturated limestone and sandstone samples (four each) with a mineralization factor of 1%. When the electric field was switched on, all samples demonstrated an approximately 0.2% decrease in acoustic field velocity. In the 2–200 kHz frequency range, the velocity decrease does not depend on frequency for all limestone and sandstone samples. It is shown that the modified apparatus can reliably detect the electroseismic effect without a current in a sample, despite the fact that its value exceeds the sensitivity threshold by only 20–25 dB. Field coherence makes it possible to measure the relaxation time of the acoustic field velocity after an electric field without a current in a sample is switched on and off. The authors demonstrate that after the electric field is switched on, the relaxation time of the acoustic field velocity does not exceed 2 ms, and after it is switched off, this value is 10–20 ms. The relaxation time difference can be used to assess the nonlinearity of the electroseismic effect of the first kind.

The paper describes the automated seismic monitoring system for the European Arctic based on an international seismic network located in the region. The core of the system is the NSDL software package developed by the authors for automated detection and location of seismic events. NSDL is designed to automatically monitor the seismic activity of a region using a seismic network, seismic arrays, or individual three-component seismic stations. The described system has two levels. The first level consists of single-station data-processing programs that implement algorithms for detecting and prelocating seismic events based on data from individual three-component seismic stations and arrays. The second level is a program for associating individual station data-processing results, which performs joint location over the network based on events and phases of seismic waves detected at the first processing level. NSDL makes it possible to use a set of 1D layered velocity models for locating remote events the wave propagation paths from which cross regions of the medium with different velocity properties. Decisions about the truth or falsity of the detected candidate events are made with a Bayesian classifier based on the evaluation of a number of amplitude, spectral, and polarization parameters both for single-station and joint (network) processing of seismic events. The use of the seismic monitoring system for the Arctic region showed high reliability of automatically obtained results, significantly sped up the compilation of the final analyst-verified catalogs, and significantly increased the representativeness of the resulting bulletin due to weak events. The level of detail achieved by the described system makes it possible to take a fresh look at the development and structure of the seismic process in the European Arctic and in particular to record seismic events associated not only with tectonic processes but also with cryospheric destruction processes.

The history of science abounds in examples when misconceptions dominated the scientific community and did it significant harm. New ideas in science have always cut their paths with great difficulty. Inertial thinking and the temptation to adhere to stereotypes often hamper the development of knowledge and lead to erroneous interpretations of experimental data. Often a scientist has to face the skepticism of his colleagues and even the distrust of the community. Moreover, if new knowledge contradicts the established methodological schemes that are generally accepted in a particular scientific field, a creator of innovations can almost inevitably expect attack. Misconceptions inhibit, but sometimes lead to the development of our knowledge in understanding processes occurring deep in the Earth’s interior. These examples, of course, do not exhaust all misconceptions in the earth sciences, and any researcher, if desired, can easily supplement this list. Misconceptions in science culminate in researchers obtaining incorrect results or simply hitting a dead end. Thus, if the coordinates of hypocenters are incorrectly determined, a subsequent chain of incorrect conclusions arises when studying particular regions. In addition to the objective consequences of misconceptions, subjective consequences cause considerable harm. Subjective consequences entail the effect of when individual scientists are held captive by misconceptions—due to ignorance or misunderstanding of individual aspects of certain problems—on the emergence of new ideas and approaches in a particular field. Most often, this manifests itself when scientists review articles and dissertations by their peers. In this article, the author gives several examples of misconceptions, which, in his opinion, are typical of the field in which he has worked for many years. In particular, this concerns misconceptions related to determining the hypocentral coordinates of earthquakes, seismic tomography, the inverse dynamic problem, reversal of seismic wave travel-time curves, etc. Twelve misconceptions are considered in all, which in one way or another affect the development of alternative methods for interpreting seismological data and our understanding of the Earth’s structure.

The first regional attenuation relationship of peak ground accelerations is developed for Sakhalin Island based on data from a strong motion network and local network of seismometers. The applicability limits and standard error of the relationship are determined. The developed relationship is recommended for use in seismic hazard assessments for Sakhalin Island and the adjacent shelf, including updating of general seismic zoning maps. The ground motion prediction equation models calculated for other Earth regions suitable for Sakhalin are selected.

Previous results on the location of crustal earthquake foci in the Caucasus clearly show that the methods used in seismic service practice to determine the hypocenters of earthquakes do not allow accurate localization of events and can hardly be used to forecast earthquakes or study the structure of the Earth’s crust and upper mantle in detail. The arrival times of seismic waves often have large errors that prevent qualitative processing of observations and, therefore, is is difficult to obtain reliable results. In addition, the use of only one velocity curve or one set of travel-time curves for all stations of the network hinders accurate determination of the location of earthquake hypocenters. In order to localize earthquake foci with high precision, it is also necessary to have a sufficiently detailed representation of the structure of the Earth’s crust and upper mantle in the studied region. It is also desirable to take information about the structure of the region not from earthquake data, but based on other observations, e.g., deep seismic sounding (DSS) data. Using seismological bulletins for 1970–2015, we have redetermined the hypocentral coordinates of crustal earthquakes in the Caucasus. The new distribution of crustal earthquake hypocenters in the Caucasus differs significantly from the old distribution obtained from the catalog. This may become the basis for refining ideas about the regional geodynamics.

The paper considers the problem of seismic treatment in building codes. Some definitions used in earthquake engineering in Russia and abroad are analyzed. Inconsistencies between definitions and empirical data and similarity and dimensional theory are revealed. Seismic treatment is still based on different assumptions that were made during in the early days of engineering seismology and earthquake engineering despite advances in modern seismology in theoretical problems and a representative strong ground motion database. Many of these assumptions were made in violation of the rules of similarity and dimensional theory, and these errors migrated to modern building codes. For example, the definitions of magnitude, duration of vibrations, quality factor, ground accelerations, and some other quantities used in regulations in the engineering scope of seismic ground motion turned out to be incorrect. This is because many definitions valid for small deformations are incorrect for large ones. Confusion with terminology causes many problems: definitions of some quantities (e.g., the duration of vibrations or the vibration period) used in calculations depend on the posed problem. There are both identical definitions for different physical quantities and different definitions for the same quantity even in the glossaries of regulations. Physically incorrect definitions of some quantities that can lead to incorrect engineering calculation results are a significant source of calculation errors. The paper considers dimensionless quantities that describe seismic ground motion. Dimensionless quantities do not depend on the scale of the phenomenon according to similarity and dimensional theory. Therefore, the use of seismic treatment characteristics, such as the dynamic amplification factor, deformation, shape of the response spectrum, shape of the vibration envelope, and number of vibration cycles, greatly increases calculation accuracy.