Vol 53, No 4 (2017)

The seismological data on the destructive Taiwan earthquake of February 5, 2016, (MS = 6.5) are analyzed. The source rupture length is estimated by different techniques using P-waves spectra at teleseismic distances, azimuthal hodograph, and distribution of mb magnitude. The obtained results agree with each other.

Low-frequency deconvolution of precise digital records of seismic and industrial vibrations allows significant expansion of the frequency range of electrodynamic geophones, limited only by the deconvolution noise, which is represented by increased instrumental noise. A dependence of deconvolution noise on the decrease rate of a sensor’s natural frequency and the level of initial instrumental noise is assessed theoretically. A method and a simple stand for the experimental evaluation of deconvolution quality are proposed and an example of a hundredfold virtual decrease in natural frequency of the sensor used in the real record is presented.

The problems and procedures for obtaining high quality results of multidisciplinary geophysical monitoring at the stage of preliminary data processing are considered. The case study of solving different technical problems during the long-term multidisciplinary borehole geophysical observations at the Petropavlovsk- Kamchatsky geodynamic research area is described. The algorithms for preliminary data processing and flawed data discard combining automated approaches and expert screening developed by the authors are presented. Suppression of quasi-regular disturbances is especially important in the studies of interrelations between geoacoustic, electromagnetic, and meteorological processes and seismicity because of the clear diurnal periodicity in all these processes that significantly complicates the signal extraction from the noise. The key technical, organizational, and methodical measures aimed at improving the data should be provided at the project planning stage of the measurement system. The optimal selection and reasoned application of special procedures for data preprocessing can crucially affect the research results.

The paper considers the Argun earthquake of July 22, 2011 (M_w = 4.5), which occurred in the Argun River valley in a low-seismicity territory in China. The focal parameters of the earthquake (depth of the hypocenter, moment magnitude, scalar seismic moment, and focal mechanism) were determined by calculating the seismic moment tensor from the amplitude spectra of surface waves and the data on the signs of the first arrivals of body waves at regional stations. The solution of the focal mechanism makes it possible to assume a relationship between the earthquake focus and a fault with a northeastern strike bordering the southeastern side of the Argun Basin (in Chinese territory). The Argun earthquake was felt in Russia with an intensity of II–III to V at the epicentral distances up to 255 km. The intensity of shaking did not exceed values suggested by new GSZ-2012 and GSZ-2014 seismic zoning maps of Russian territory. Nevertheless, the question on the possible occurrence of stronger earthquakes in the studied region remains open.

The daily periodicity in four regions of the Dushanbe–Vakhsh area is analyzed. The study considers representative, nonrepresentative, and intermediate-energy earthquakes. Analysis of the specific features of the shape of the diurnal variation on workdays and weekends make it possible (1) to reliably conclude that the anomalous daily variation on workdays in medium-energy earthquake samplings is of technogenic origin and (2) suggest similarities in samplings of the weakest and strongest earthquakes. Apparently, the catalog includes a large number of industrial blasts. The number of blasts in earthquake samplings of various epochs and energies is estimated.