Patterns in the daily periodicity of low magnitude seismicity in Kamchatka

A daily periodicity in small (K ≤ 8. 0) Kamchatka earthquakes has been detected, with the maximum occurring during the nighttime. The effect was not observed throughout the area of study, but only in several zones. We show that the results are not affected by human and weather factors. A hypothesis is put forward to explain the physical causes of the effect, viz., that the daily periodicity of small earthquakes could be due to natural VLF electromagnetic radiation acting on the geologic medium. It is pointed out that the effect is related to the previously identified effect of natural electromagnetic radiation modulating the intensity of geoacoustic emission from rocks.     

Propagation of the Rossby waves on two dimensional rectangular grids

Summary A simple two-dimensional quasi-geostrophic linearized model of the atmosphere is used to investigate the behaviour of the quasi-geostrophic modes for five horizontal rectangular grids. Numerical expressions for frequencies of Rossby waves for all grids are evaluated. It was found that the B and C grids produce only negative frequencies as well as the continuous case. The D grid has negative and zero frequencies. Finally, it was found that the A and E grids produce positive frequencies and eastward moving Rossby waves.With 2 Figures     

The Požarevac loess–paleosol sequence: a record of increased aridity in the south-eastern margin of the Carpathian Basin during the last 350 ka

The loess sequence preserved in the Požarevac brickyard in north-eastern Serbia comprises eight loess units separated by seven paleosols. Geochronological investigation using amino acid racemization and luminescence dating support stratigraphic correlations of loess units L3, S2LL1 and L1 at the Požarevac section with loess of glacial cycles E [Marine Isotope Stage (MIS) 10], D (MIS 9–8), C (MIS 7–6) and B (MIS 5–2) across central Europe. Correlation with the marine oxygen-isotope stratigraphy and associated paleoclimatic inferences are further supported by magnetic susceptibility, particle size and carbonate content measured in Požarevac sediments. Malacological investigations at the Požarevac section reveal the continuous presence of the Chondrula tridens and Helicopsis striata faunal assemblages throughout the last 350 ka. The loess malacological fauna, which is characterized by the complete absence of cold-resistant and cold-preferring species, suggests a stable, dry and relatively warm glacial and interglacial climate, compared with other central European loess localities. Together these data suggest that the south-eastern part of the Carpathian (Pannonian, Middle Danube) Basin was a refugium for warm-preferring and xerophilous land-snails during the generally unfavorable glacial climates of the late Middle and Late Pleistocene.     

The mechanism of modulation of geoacoustic emission intensity by weak electromagnetic fields in the audio-frequency range

We propose a physical mechanism explaining the mechanism of modulation of the geoacoustic emission intensity by an external electromagnetic field in the audio-frequency range, which was previously revealed as a result of borehole measurements at the Petropavlovsk-Kamchatskii geodynamic testing area. It was established that electric double layers (EDL) at the interface between solid and liquid phases in a fluidsaturated geological medium play a key role in the mechanism proposed.     

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.     

The K–Ar and Rb–Sr Isotopic Systems in Rocks from the Jurassic Terrigenous Complex of the Greater Caucasus

The behavior of K–Ar and Rb–Sr isotopic systems in clayey rocks from the Jurassic terrigenouis complex of the Greater Caucasus sampled along the Terek River is discussed. It is shown that the rocks experienced intense postdiagenetic alterations accompanied by substantial changes in mineral composition and K–Ar and Rb–Sr isotopic systems. Lateral stress is the leading factor responsible for secondary mineral and geochemical transformations of rocks in cleavage zones. Rejuvenation of the radiological age of rocks, relative to their stratigraphic age, is 100 Ma and more. The age estimate of approximately 50 Ma obtained for samples from the southern limb of the anticlinorium reflects the Paleocene–Eocene phase of tectonic activity manifested in both the Caucasus and other areas of the Mediterranean foldbelt.     

The Early Cretaceous Anoxic Basin of the Russian Plate: Sedimentology and Geochemistry

The profile comprising a series of lower Aptian sections from Ul'yanovsk to Saratov in the Russian Plate has been studied. It is shown that the unit of organic-rich rocks is characterized by the lack of bioturbation and elevated concentration of many chemical elements. The petrography and geochemistry of organic matter (OM) indicate the prevalence of basinal OM in carbonaceous sediments, while continental OM dominates in host rocks. Sedimentological, biotic, and geochemical data testify to the deposition of organic-rich sediments under anoxic conditions. The anoxic environment in the Aptian basin of the Russian Plate correlates with the global OASE-1a anoxic event. The mechanism of Aptian carbonaceous sedimentation is discussed.     

Estimate of Variations in the Parameters of the Midlatitude Lower Ionosphere Caused by the Solar Flare of September 10, 2017

Geomagnetism and Aeronomy - Changes in the state of the D and E ionospheric regions lead to variations in the amplitude-phase characteristics of VLF radio signals. The existing theoretical and...     

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.