Relationship of high-frequency geoacoustic emission and electric field in the atmosphere in seismotectonic process

In July–October 2006 and 2007, combined measurements of geoacoustic emission in the range of 2.0–6.5 kHz, the electric field in the atmosphere near the ground, and meteorological values were carried out in Kamchatka. Using the nonparametric method of Spearman’s correlation analysis, the relationship between their average hourly values was examined. After excluding results of bad weather (rain, strong and moderate wind, low atmospheric pressure), a highly important negative relation between disturbances in geoacoustic emission and the electric field were detected. Most probably, it was caused by amplification of the strain of near-surface sedimentary rocks at the observation point during a seismotectonic process. The revealed relation is evidence for another manifestation of the lithosphere’s influence on surface atmosphere in a seismoactive region.     

Seismoacoustic emission and electromagnetic radiation of fractured rocks in deep wells

The results of simultaneous measurements in seismoacoustic emission (SAE) and electromagnetic radiation (EMR), carried out with the help of a program-apparatus complex developed at the Institute of Geophysics, Ural Division, Russian Academy of Sciences, are considered. Measurements have been carried out in the wells with varied structures located in Karelia, Yamal-Nenets Autonomous Area, and Kamchatka. It has been shown that intervals of fractured rocks are simultaneously recorded in anomalies of SAE and EMR signals. This fact allows us to detect these zones of high tensosensitivity in a geomedium volume for the purposes of monitoring in geodynamic phenomena in the Earth’s crust.     

On global forces of nature driving the Earth’s climate. Are humans involved?

The authors identify and describe the following global forces of nature driving the Earth’s climate: (1) solar radiation as a dominant external energy supplier to the Earth, (2) outgassing as a major supplier of gases to the World Ocean and the atmosphere, and, possibly, (3) microbial activities generating and consuming atmospheric gases at the interface of lithosphere and atmosphere. The writers provide quantitative estimates of the scope and extent of their corresponding effects on the Earth’s climate. Quantitative comparison of the scope and extent of the forces of nature and anthropogenic influences on the Earth’s climate is especially important at the time of broad-scale public debates on current global warming. The writers show that the human-induced climatic changes are negligible.     

Fluctuations in the angular momentum of the atmosphere and intraday irregularities in the Earth’s rotation

Numerical celestial-mechanical models are used to compare (andg interpolate and forecast) near-diurnal tidal variations in the Earth’s axial rotation and oscillations in the global angular momentum of the atmosphere using the IERS data and NCEP/NCAR meteorological data. In order to improve the accuracy of interpolations and forecasts made for short and intraday time intervals, it is expedient to include the effect of small perturbations in short-term zonal tides, which influence fluctuations in Universal Time UT1 directly related to the Earth’s rotation. Due to the quasi-static formulation of the problem, it is assumed that the dynamics of the thin surface atmosphere are completely determined by the gradient of the tide-generating geopotential, which supports forced oscillations of the entire subsystem (i.e., of the mantle and atmospheric envelope). A comparison of the numerical simulations with the NCEP/NCAR data shows that the model is effective for applications in forecasting atmospheric tides.     

Genetic relations between meteorites and terrestrial and lunar rocks

According to their genesis, meteorites are classified into heliocentric (which originate from the asteroid belt) and planetocentric (which are fragments of the satellites of giant planets, including the Proto-Earth). Heliocentric meteorites (chondrites and primitive meteorites genetically related to them) used in this study as a characteristic of initial phases of the origin of the terrestrial planets. Synthesis of information on planetocentric meteorites (achondrites and iron meteorites) provides the basis for a model for the genesis of the satellites of giant planets and the Moon. The origin and primary layering of the Earth was initially analogously to that of planets of the HH chondritic type, as follows from similarities between the Earth’s primary crust and mantle and the chondrules of Fe-richest chondrites. The development of the Earth’s mantle and crust precluded its explosive breakup during the transition from its protoplanetary to planetary evolutionary stage, whereas chondritic planets underwent explosive breakup into asteroids. Lunar silicate rocks are poorer in Fe than achondrites, and this is explained in the model for the genesis of the Moon by the separation of a small metallic core, which sometime (at 3–4 Ga) induced the planet’s magnetic field. Iron from this core was involved into the generation of lunar depressions (lunar maria) filled with Fe- and Ti-rich rocks. In contrast to the parent planets of achondrites, the Moon has a olivine mantle, and this fact predetermined the isotopically heavier oxygen isotopic composition of lunar rocks. This effect also predetermined the specifics of the Earth’s rocks, whose oxygen became systematically isotopically heavier from the Precambrian to Paleozoic and Mesozoic in the course of olivinization of the peridotite mantle, a processes that formed the so-called roots of continents.     

Internal waves in the near-bottom thermocline and microdeformations in the Earth’s crust in the continent-ocean transition zone

The results of synchronous measurements of temperature variations in a near-bottom thermocline, as well as microdeformations of the Earth’s crust and atmospheric pressure pulsing, recorded on-shore with the help of a laser strainmeter and laser nanobarograph, are presented. A string containing 20 thermosensors spaced at 0.5 m was used; it was placed by an anchored buoy in a place with 21-m depth and 500 m away from the shore. A good correlation between microdeformations and atmospheric pressure variations was observed for periods longer than 6 h. Quantitative estimates and spectral analysis via the Gilbert-Huang method for investigation of nonstationary and nonlinear processes lead to the conclusion that, on temporal scales from tidal to several minutes, the predominant way of formation of microdeformations in the Earth’s crust can be breaking of internal waves in a thermocline that leads to shallow water (i.e., in the zone of “internal breakers”).     

Magma degassing during 7600 14C Kurile Lake caldera-forming eruption and its climatic impact

The main goal of this investigation is estimating volume of volatile emission, atmospheric and climatic impact of the Kurile Lake caldera-forming eruption, one of the Earth’s largest Holocene explosive eruptions. The volatile content of magma before the eruption was estimated by comparing H₂O, S, Cl and F contents in natural quenched glassy melt inclusions trapped by plagioclase phenocrysts. The volatile content of igneous rocks after eruption was estimated by comparing concentrations of degassed matrix glasses. As a result of KO-eruption not more than (3.7–4.2) × 10¹² kg of water, (4.3–4.9) × 10¹⁰ kg of chlorine, (8.6–9.8) × 10⁹ kg of fluorine and (2.6–2.9) × 10¹⁰ kg of sulphur were injected into the atmosphere. This eruption had to produce an important climatic impact.     

Greenhouse gases and greenhouse effect

Conventional theory of global warming states that heating of atmosphere occurs as a result of accumulation of CO₂ and CH₄ in atmosphere. The writers show that rising concentration of CO₂ should result in the cooling of climate. The methane accumulation has no essential effect on the Earth’s climate. Even significant releases of the anthropogenic carbon dioxide into the atmosphere do not change average parameters of the Earth’s heat regime and the atmospheric greenhouse effect. Moreover, CO₂ concentration increase in the atmosphere results in rising agricultural productivity and improves the conditions for reforestation. Thus, accumulation of small additional amounts of carbon dioxide and methane in the atmosphere as a result of anthropogenic activities has practically no effect on the Earth’s climate.     

A dipole model of generating electric pulses in relaxation processes in the Earth’s crust

A new numerical model of generating electric pulses in the Earth’s crust with use of a system of electric dipoles that are located uniformly over an active surface of the structural block relaxing after its constrained turn is developed. Electric moments of dipoles change with time according to the amplitude of differential movements. It is shown that the amplitude of electric pulses and the degree of their attenuation with distance to the source are in agreement with the data of results of instrumental observations.     

Mantle plume tectonics: The evolution of the main ideas

Three stages of the evolution of plume-tectonic ideas and views are examined for the first time using five important criteria: (1) the area of magmatic occurrence at the Earth surface; (2) the pecularities of the geochemical compositions of igneous rocks that are associated with plumes; (3) stationary position relative to the Earth’s core; (4) correspondence to the lithospheric structure; and (5) correspondence to the cyclicity of the lithosphere’s evolution. The conception of a relationship between the mechanisms of plume and plate tectonic is very important for the global geodynamic theory and for interpretation of intraplate magmatism and some lithospheric structures linked with them.     

Instrumental study of high-frequency seismoacoustic signal modulation in a deep drillhole

For many years we have failed to record instrumentally the background variations in seismoacoustic emission in solid consolidated rocks of the Earth’s crust at great depths (3200 m) and to confirm their relation to lunar-solar gravitation. We managed to fulfill the task only with significantly improved parameters of the recording system measurement channel. As follows from analysis of new data, the amplitudes in the diurnal cycle vary from 1930 to 2100 fm (10⁻¹⁵) for the band of 160 Hz and from 129.5 to 132 fm for the band of 500 Hz, while the energy model correlation coefficients are within 0.737–0.852. Hence, this fact proves once again that background variations related to lunar-solar tides are universal in occurrence, and their frequency and amplitude depend significantly on the host rocks, position, and time of observations, while the energy model fits in these variations.     

Observations of ultra-low-frequency geomagnetic disturbances reflecting the processes of the preparation and development of tsunamigenic earthquakes

Analysis of experimental observations of the Earth’s magnetic field variations recorded by the scientific instruments at the Northern Caucasus Geophysical Observatory of the Institute of Physics of the Earth, Russian Academy of Sciences, in the period 2007–2009 was performed. It was found that the characteristic ultra-low-frequency (ULF) waveforms of the geomagnetic disturbances were distinguished in the structure of the observed variations that reflect the process of preparation and development of a tsunamigenic earthquake.     

Spectral harmonic analysis and synthesis of Earth’s crust gravity field

We developed and applied a novel numerical scheme for a gravimetric forward modelling of the Earth’s crustal density structures based entirely on methods for a spherical analysis and synthesis of the gravitational field. This numerical scheme utilises expressions for the gravitational potentials and their radial derivatives generated by the homogeneous or laterally varying mass density layers with a variable height/depth and thickness given in terms of spherical harmonics. We used these expressions to compute globally the complete crust-corrected Earth’s gravity field and its contribution generated by the Earth’s crust. The gravimetric forward modelling of large known mass density structures within the Earth’s crust is realised by using global models of the Earth’s gravity field (EGM2008), topography/bathymetry (DTM2006.0), continental ice-thickness (ICE-5G), and crustal density structures (CRUST2.0). The crust-corrected gravity field is obtained after modelling and subtracting the gravitational contribution of the Earth’s crust from the EGM2008 gravity data. These refined gravity data mainly comprise information on the Moho interface and mantle lithosphere. Numerical results also reveal that the gravitational contribution of the Earth’s crust varies globally from 1,843 to 12,010 mGal. This gravitational signal is strongly correlated with the crustal thickness with its maxima in mountainous regions (Himalayas, Tibetan Plateau and Andes) with the presence of large isostatic compensation. The corresponding minima over the open oceans are due to the thin and heavier oceanic crust.     

Sedimentary and Geochemical Characteristics of Sinian Cap Carbonates in the Upper Yangtze Region

A global-scale glaciation occurred at about 600 Ma ago. As a result, the Earth became the “Snowball Earth“. The glaciation came to the end abruptly when atmospheric carbon dioxide increased to such an extent as to be about 350 times the modem level because of subaerial volcanic degassing. The rapid termination of glaciation would have led to warming of the Snowball Earth and extreme greenhouse conditions would have been created. The transfer of atmospheric carbon dioxide to oceans would give rise to the rapid precipitation of calcium carbonate in warm surface seawaters, thus forming the cap carbonate rocks as observed worldwide today. Regionally persisting, thin layers of carbonate rocks directly and ubiquitously overlie Proterozoic glacial deposits almost on every continent, and are commonly referred to as cap carbonates. Their unusual litho- fabrics, stratigraphically abrupt basal and upper-level contacts and strongly negative carbonate isotopic signatures ( δ ^13Cearb. values range from -7.0‰ —0‰) suggest a chemical oceanographic origin, the details of which remain unknown. It is proposed that these enigmatic deposits are related to the destabilization of gaseous hydrate in terrestrial permafrost following rapid postglacial warming and flooding of widely exposed continental shelves and internal basins. The authors carried out studies on the geochemistry, sedimentology and palacontology of the Sinian cap carbonates in Guizhou and Hunan provinces, including the occurrence of cap carbonates of unusual fabrics, strongly negative carbon isotopic signatures, and a lot of bitumen nodules.From the results it is suggested that the cap carbonates were formed from solid methane seepage, and it is in agreement with Kennedy‘‘ s viewpoint (2001) that the cap carbonates resulted from the rapid precipitation of calcium carbonate in response to solid methane seepage.     

Development of methods for constructing models for intra-year irregularity in the Earth’s rotation

The development of methods for the construction of stochastic, dynamical models for intra-year irregularity of the Earth’s rotation is considered. A correlational model based on harmonically additive and parametrically random, colored and broadband, gravitational-tidal perturbations from the Sun and Moon is developed. One-dimensional and multi-dimensional characteristic functions are found for the case of Gaussian and non-Gaussian colored and broadband fluctuations in the irregularity of the Earth’s rotation. Examples of computer modeling of the irregularity in the Earth’s rotation based on a priori and a posteriori IERS data are presented.     

Sedimentation rhythmicity as a reflection of astronomical cyclicity

The Mesozoic-Cenozoic rhythmic continental sedimentary rocks are analyzed for every particular period and epoch from the Triassic to the Pliocene. The maximal distribution areas of rhythmic deposits are within the latitudinal zone of 20°-40°. Investigation of rhythmic Mesozoic-Cenozoic carbonate-containing deposits of Europe and North America enables us to attribute rhythmicity to climate change owing to insolation and eustatic variations of oceanosphere’s level, on the one hand, and to compare duration values of the rhythmic unit and rhythmic sequence with cycles of orbital precession, ecliptic plane inclination, and the eccentricity of the Earth’s orbit, on the other hand.     

Geoacoustic emission response to deformation processes activation during earthquake preparation

The results of geoacoustic emission investigations carried out on the seismoactive Kamchatka Peninsula since 1999 are presented. The experiments are characterized by the application of broadband piezoceramic sound receivers (hydrophones) for recording the emission. The hydrophones were installed at the bottom of natural and artificial water reservoirs. As compared with the standard hydrophones, such receivers allow us to broaden the registration frequency range up to 0.1 Hz–11 kHz. Three-component vector receivers with the same frequency range were used simultaneously to study the spatial structure of the geoacoustic emission and the mode of the medium particle movement in a wave. In the course of the investigations, it was established that anomalies of the geoacoustic emission in the kilohertz frequency range are recorded 1–3 days before strong earthquakes at a distance of a few hundred kilometers from the epicenter. A sharp increase in the amplitude and frequency of the geoacoustic impulses, which resemble microearthquakes in pattern and last from tens of minutes to several hours, is interpreted as an anomaly. Signals at such frequencies cannot propagate from the epicenters of preparing earthquakes and represent the response of the medium at the registration point to the change of its stress-strain state. The stress field created therein determines the primary orientation of the emission sources, which can be assessed by vector-phase methods. The results of the integrated investigations of the geoacoustic emission and the Earth’s surface deformation revealed that anomalies are observed before earthquakes with a considerable increase in the strain rate during both the compression and extension of the near-surface rocks.     

Interaction between a mafic melt and host rocks during formation of the Kivakka layered intrusion,North Karelia

The study of interaction between mantle melts and crustal rocks is of great importance for deciphering the evolution of the Earth’s crust and for better understanding the composition of mantle sources, in particular, the degree of their compositional heterogeneity. This work presents the results of Rb-Sr and Sm-Nd isotopic studies of 37 samples taken from the Kivakka layered intrusion, host rocks, and rocks at the contact. The studies were aimed at verifying the hypothesis of possible crustal contamination of mafic melt during magma chamber crystallization. It was found that the section of the Kivakka layered massif is characterized by initial Sr and Nd isotopic heterogeneity, with negative correlation between initial Nd isotopic ratio and its content. The rocks of the massif have low ɛ_Nd(T) values.     

Some improved methods for modeling the Earth’s polar motion

Some improved methods for modeling the motions of the Earth’s pole determined by gravitational-tidal, fluctuating-dissipative perturbations occurring on various time scales are presented. The main attention is paid to dynamical linear-regression models and dynamical filtering models, which take into account dynamical measurement errors. Computer simulations of the oscillatory motion of the Earth’s pole for 1995–2010 are also presented.     

Geoacoustic inversion using adaptive neuro-fuzzy inference system

The geoacoustic parameters form significant input for underwater acoustic propagation studies and geoacoustic modeling. Conventional inversion techniques commonly used as indirect approach for extraction of geoacoustic parameters from acoustic or seismic data are computationally intensive and time-consuming. In the present study, we have tried to exploit the advantage of soft computing techniques like, reasoning ability of fuzzy logic and learning abilities of neural networks, in inversion studies. The network model based on the combined approach called adaptive neuro-fuzzy inference system (ANFIS), is found to be very promising in inversion of the acoustic data. The network model once built is capable of invert a few thousand data sets instantaneously, to a reasonably good accuracy. In the case of conventional approaches, repetition of the entire inversion process with each new data set is required. A limited number of sensor’s data are sufficient for simulation of the network model and provides an advantage to use short hydrophone array data. Inversion results of a few hundred test data sets, representing different geoacoustic environments, show the prediction error is much less than 0.01 g/cc, 10 m/s, 10 m and 0.1 against first layer’s density, compressional sound speed, thickness and attenuation respectively for a three-layer geoacoustic model. However, the error is relatively large for the second- and third-layer parameters, which need to be improved. The model is efficient, robust and inexpensive.