Circular geomorphologic and geological features in the Japanese islands

The available geomorphologic, geological, geophysical, and paleogeographic data were used to identify and reconstruct, to varying degrees of accuracy, dome-block and tectono-magmatic circular uplifts within the Japanese island arc, which contain the main mountain massifs and the centers of orogenic granitoid magmatism on Kyushu, Honshu, Shikoku, and Hokkaido islands. By analogy with the magmatic domes of mountain features in the adjacent continental land (Sikhote-Alin’), they are identified with Cretaceous/Paleogene granitoid focus systems of regional rank. It was found that these elements of the structural setting have preserved their significance up to the present, in spite of the fact that destructive tectonogenetic tendencies have been dominant since the Late Oligocene/Miocene. We also hypothesize that relicts of a major dome-block feature (Nampo) exist within the northern Philippine Sea. The local circular features on these islands reflect the entire diversity of focus formations at volcanic arcs and in the volcano-plutonic belts at active continental margins. Our study showed that the morphotectonic base of the Japanese Islands is not a chaotic collage of terranes, but rather a consolidated system of Cretaceous/Paleogene central-type orogenic uplifts that are evolving in an inherited manner with superimposed Late Cenozoic magmatic, block, and fault features. The Japanese Islands contain an abundance of circular features of varying ranks and ages, indicating the essential control of deep injected dislocations and of the magmatic factor in the structure and evolution of the region.     

The State and Dynamics of the Ionosphere from Synchronous Records of ULF/VLF and HF/VHF Radio Signals at Geophysical Observatory “Mikhnevo”

Izvestiya, Physics of the Solid Earth - Abstract—Studying the spatiotemporal dynamics of the disturbances in the atmosphere, upper, and lower ionosphere requires integrated investigation of...     

The influence of hydrometeorological factors on the results of geophysical monitoring conducted at the Petropavlovsk-Kamchatskii Geodynamic Test Site

A local model has been developed for the Petropavlovsk-Kamchatskii Geodynamic Test Site; the model is concerned with the transformation of atmospheric precipitation in the snow cover and in the active soil layer. The input parameters of the model are standard hydrometeorological observations, the output consists in the variation of moisture content in the soil and evaporation from it. Data from water level monitoring carried out at the Site for the purpose of earthquake prediction were used to show how the output parameters can be utilized to reveal the water level variations in a well due to the moisture content variation in the upper crust. The procedure makes the data interpretation more correct.     

Spatiotemporal distributions of the electron density in the ionosphere by records of the total electron content and phase of VLF radio signals

Features of the structure and dynamics of the ionospheric plasma are studied in a comparison the ionospheric total electron content measurements with the phase and amplitude measurements of VLF–LF radio signals on global and regional paths. The ionospheric structure over Europe is reconstructed. The spatiotemporal dynamics of moving ionospheric disturbances under conditions of a powerful geomagnetic storm of March 17, 2015, is examined based on the reconstruction results. Analysis of the phase variation of VLF radio signals, together with the TEC measurement data, is not only an additional tool in the study of the dynamics of ionospheric disturbances; it also makes it possible to estimate electron density disturbances in different ionospheric layers.     

Cross-correlation earthquake precursors in the hydrogeochemical and geoacoustic signals for the Kamchatka peninsula

We propose a new type of earthquake precursor based on the analysis of correlation dynamics between geophysical signals of different nature. The precursor is found using a two-parameter cross-correlation function introduced within the framework of flicker-noise spectroscopy, a general statistical physics approach to the analysis of time series. We consider an example of cross-correlation analysis for water salinity time series, an integral characteristic of the chemical composition of groundwater, and geoacoustic emissions recorded at the G-1 borehole on the Kamchatka peninsula in the time frame from 2001 to 2003, which is characterized by a sequence of three groups of significant seismic events. We found that cross-correlation precursors took place 27, 31, and 35 days ahead of the strongest earthquakes for each group of seismic events, respectively. At the same time, precursory anomalies in the signals themselves were observed only in the geoacoustic emissions for one group of earthquakes.     

Climatological monthly characteristics of middle atmosphere gravity waves (10 min-10 h) during 1979–1993 at Saskatoon

Saskatoon (52° N, 107°W) medium frequency (MF) radar data from 1979 to 1993 have been analyzed to investigate the climatology of irregular wind components in the height region 60–100 km. This component is usually treated in terms of internal gravity waves (IGW). Three different band-pass filters have been used to separate the intensities of IGWs having periods 0.2-2.5; 1.5-6 and 2–10 h, respectively. Height, seasonal and inter-annual variations of IGW intensities, anisotropy and predominant directions of propagation are investigated. Mean over 14 years’ seasonal variation of the intensity of long-period IGWs shows a dominant annual component with winter maximum and summer minimum. Seasonal variations of the intensity of short-period waves have a strong semi-annual component as well, which forms a secondary maximum in summer. Predominant azimuths of long-period IGWs are generally zonal, though they vary with season. For short-period IGWs, the predominant azimuth is closer to the meridional direction. Anisotropy of IGW intensity is larger in summer, winter and at lower altitudes. The IGW intensity shows apparent correlation with both solar and geomagnetic activity. In most cases, this correlation appears to be negative. The variations versus solar activity is larger for longer-period IGW. Possible reasons and consequences of the observed climatological variations of IGW intensity are discussed.     

Results from field and stationary tests of the seismic signal recorder Delta 03

The operation of a new domestic seismic signal recorder Delta 03 is analyzed. The optimization of technical requirements on parameters of the recorder, the test cycle, adjustment in the process of testing individual technical solutions, and improvement of the device were carried out in close cooperation with its designers from OOO Logic Systems (Ramenskoye, Moscow Region). At the time of writing, the recorder Delta 03 is a robust device that is recommended for use in seismic monitoring systems of various levels.     

Comparison of the geoacoustic measurements in boreholes with the data of laboratory and in-situ experiments on electromagnetic excitation of rocks

The data of borehole geoacoustic and electromagnetic measurements in Kamchatka are compared with the results of laboratory and field experiments on electromagnetic excitation of rocks. A noticeable similarity in the responses of the natural geological medium and rock specimens is observed. The field experiments with controlled electromagnetic sources show that the geophones placed in boreholes are capable of reliably detecting the responses of rocks in situ to electric impacts as low as 0.5 mV/m. The obtained results provide the experimental evidence in favor of the previously proposed hypothesis of modulation of geoacoustic emission in rocks in situ by the ULF atmospheric electromagnetic field.