The first part of this work discussed the software requirements for working with geophysical monitoring data. This paper considers the technology for studying similar signals realized in the WinABD program. In contrast to many statistical analysis programs, WinABD supports a complete cycle of operations necessary for working with experimental time series. The software includes a database management system, a powerful research apparatus, and an interactive data visualization environment. The program makes it possible to analyze the structure of series and reveal dependences and interrelations between signals. There are a large number of nonstandard tools and methods necessary for everyday work with nonideal data. A moving time window technology is widely used, which makes it possible to study the development of all processes with time and reveal variations related to any events. A special “window-slamming” technology at the boundaries of a series makes it possible to carry out processing with a decreasing length of the series, which allows arbitrary combination of the applied methods. All of the procedures admit the presence of gaps in observations. For all data operations, a calendar time scale is used, which substantially improves convenience of operation. Correct joint processing of series with unidentical onset dates and noncoinciding observation periodicity is provided.

Time series of geophysical monitoring data are very specific. They can contain complicated irregular variations and nonstationary effects of various kinds. Time-varying noise, numerous gaps in the data, trends, technical drawbacks, and other hardly predictable features are often present in these time series. These peculiarities demand special methods and procedures for acquisition and analysis of the data. The first part of the paper discusses the peculiarities of the software for such time series, and a brief review of the methods for solving the task is given. In the second part of the paper, the universal software package WinABD developed by the authors for multivariable analysis of geophysical time series will be described. The technologies realized in the software package and intended for analysis of similar signals will be considered.

The diurnal periodicity of seismic events of different energy from the Greece earthquake catalog was studied. Earthquake samplings of different energy with a known level of magnitude of completeness were compiled. Parameters of the diurnal periodicity of earthquakes in different time and magnitude intervals were analyzed. Significant diurnal periodicity of earthquakes with M ≤ 4.1 was revealed. The most important result of the paper is the discovery of the diurnal periodicity of the representative earthquakes with M = 3.2–4.1. The diurnal periodicity of representative earthquakes cannot be explained at the base of the prevailing hypothesis considering the diurnal periodicity of earthquakes as an apparent phenomenon resulting from diurnal changes in the real sensitivity of the seismic network due to diurnal variations of seismic noise.

Periodograms and Fourier spectra of different experimental time series are calculated. The efficiency of the methods applied to study different signals is considered. The periodogram method often makes it possible to identify periodicities which are hardly identifiable by the Fourier analysis. First of all, it concerns the quasiperiodic processes with a considerable variability in amplitude and form of the rhythmical component, but almost constant period or very weak stable rhythm with a nonsinusoidal form. One more advantage of the periodograms is their low sensitivity to pauses and omissions in the time series. However, data preprocessing is often needed, for instance, filtration of high frequency noise, rarer data interrogation, and analysis of the rhythmical component form. The rhythms revealed by the periodogram method are commonly studied additionally to confirm their significance and to describe their properties. The low computational effectiveness, even relative to the classical Fourier transformation, is one more disadvantage of the periodogram method.

The paper presents the results of both theoretical and experimental studies carried out in the framework of the integrated problem on improving national sy