Deep Sounding Research Articles

Влияние ионосферы и неоднородной структуры Земли на поляризационные характеристики магнитного поля в диапазоне частот 0.2-200 Hz в ближней зоне горизонтальной заземленной антенны

AbstractPolarization characteristics of the field of an on-Earth emitter located at the Kola Peninsula are experimentally measured at a distance that is no greater than the height of an effective ionospheric waveguide in the FENICS-2014 experiment. Variations in the field amplitude and orientation of the major axis of polarization ellipse are observed at lower frequencies upon significant changes of the K index of geomagnetic activity. Polarization characteristics of the horizontal component of magnetic field calculated with allowance for the ionosphere and two-layer Earth structure prove the observed sensitivity of the ultralow- and lower-frequency filed in the near-field zone to the state of ionosphere at lower conductivity of underlying medium. Theoretical results are compared with the experimental data. The results are important for deep sounding of the Earth and monitoring of ionosphere with the aid of controlled low-frequency ground sources.

Geodynamics and Nature of the Conrad Boundary by Results of the Deep Electromagnetic Soundings and the Superdeep Drilling

Continental Earth’s crust is subdivided into two parts – upper, brittle crust (namely geological) and low, ductile crust (namely physical). This idea has been investigated by many researchers on the base of seismical data, laboratory study of rock specimens at high thermo dynamic conditions and on the base of theoretical speculations [1, 2, 3]. In this presentation this idea is investigated on the base of the deep soundings with powerful controlled sources such as MHD-generator “Khibiny”, industrial power transmitting lines (experiment “FENICS”) and with taking into account results of superdeep drilling on Fennoscandian shield. The summary analysis of the obtained data allows to draw a conclusion that the upper part of continental crystalline earth's crust has a thickness of the order of 10-12 km. Its principal peculiarities are: the sharp horizontal heterogeneity of electrical properties, a wide range of variations of electrical resistivity from 10 till 104 Ohm∙m, a high porosity, brittleness, and a presence of fluids (meteoric waters) that penetrate from the day time surface to the depths of up to 5-10 km. Upper crust is the most actively involved in geological processes. The low crust belongs to the depth interval from 10–12 to 35–45 km (up to the Moho boundary). It is remarkable by horizontal homogeneity of electrical properties and high electrical resistivity in the range of 105–106 Ohm∙m, by the low porosity and increased ductility. Electrical conductivity of the low crust is mostly determined by influence of planetary physical–chemical parameters (pressure, temperature, and viscosity), phase transitions of substances depending on geodynamic peculiarities of evolution for different segments of the Earth crust. As an area of physical processes influence, the low crust is nearer by its origin to the upper mantle then to the geological Earth crust. The low and upper parts of the Earth crust are subdivided between each other by the boundary of the sharp increase of electrical resistivity at the depth around 10-12 km (so called Boundary of impermeability for DC currents, BIP zone). At the same depth the sharp increase of rocks solidity, viscosity has been met in the Kola superdeep hole. This transition zone between the upper and lower crust is related with hypothetic Conrad boundary predicted by seismic data by the stepwise increase of longitudinal waves from 6 to 6.5 km/s.

Capability of low-temperature SQUID for transient electromagnetics under anthropogenic noise conditions

Transient electromagnetics (TEM) is a well-established method for mineral, groundwater, and geothermal exploration. Superconducting quantum interference device (SQUID)-based magnetic-field receivers used for TEM have quantitative advantages and higher sensitivity compared with commonly used induction coils. Special applications are deep soundings with target depths [Formula: see text] and settings with conductive overburden. However, SQUIDs have rarely been applied for TEM measurements in environments with significant anthropogenic noise. We compared a low-temperature SQUID with a commercially available induction coil in an area affected by anthropogenic noise. We acquired four fixed-loop data sets with totally 61 receiver stations close to Bad Frankenhausen, Germany. The high sensitivity of the SQUID enables low noise levels, which lead to longer high-quality transient data compared with the induction coil. The effect of anthropogenic and natural noise sources is more critical for the coil than for the SQUID data. In the vicinity of the transmitter loop, systematic distortion of the coil signals occurs at early times, most probably caused by sferic interferences. We have developed 1D inversion results of both receivers that matched well in general. However, the SQUID-based models were more consistent and showed greater depths of investigation. This led to a superior resolution of deeper layers and even enabled a potential detection of thin conducting targets at up to a 500 m depth. Moreover, we find that the SQUID data inversion revealed multidimensional effects within the conductive overburden. In this regard, we applied forward modeling to analyze systematic differences between inversion results of SQUID and coil data. We determine that low-temperature SQUIDs have the potential to significantly improve the reliability of subsurface models in suburban environments. Nevertheless, we recommend combined application of both types of receivers.

Composing the Jazz Bass Revolution: Duke Ellington’s Writing for the String Bass, 1925–1941

ABSTRACTThroughout his career, Duke Ellington (1899–1974) has been partial to the deep sounds of the bass, as evidenced by records ranging from “East St. Louis Toodle-Oo” (1926) to “Portrait of Wellman Braud” (1970). He always made sure he had the finest bassists at his disposal and used them to good advantage, not merely as accompanists or soloists, but also by having them provide counterpoint, double melodic lines, add percussive effects, and so forth. It can even be argued that although he did not play the string bass, Ellington was instrumental to its development. This article discusses the compositional devices and strategies Duke used to explore new approaches to the bass function between 1925 and 1941, and reveals how he in the process helped define its role in jazz.

Estimating muddy seabed properties using ambient noise coherence

During the Seabed Characterization Experiment, a multi-institutional field effort held at the New England mud patch, the autonomous passive acoustic lander Deep Sound made a series of ambient noise measurements from the seafloor. The instrument platform carried four hydrophones, arranged in an inverted ‘T’ shape with three spaced in the horizontal and two in the vertical, and landed on the seafloor with the bottom phones 30 cm above the interface. Pressure time series, vertical and horizontal noise coherence (directionality), were recorded continuously for periods of 9 hours over the acoustic bandwidth of 5 Hz to 30 kHz, along with the local temperature, conductivity, and depth. An analytical Pekeris waveguide noise model was fitted to the data in order to determine the bulk sound speed, sheer speed, density, and frequency dependent attenuation in the bottom fluid half-space. Acoustic properties of the mud were determined by comparing the data to the output of a range independent noise model, featuring a realistic multi-layered seabed. [Research supported by ONR.]During the Seabed Characterization Experiment, a multi-institutional field effort held at the New England mud patch, the autonomous passive acoustic lander Deep Sound made a series of ambient noise measurements from the seafloor. The instrument platform carried four hydrophones, arranged in an inverted ‘T’ shape with three spaced in the horizontal and two in the vertical, and landed on the seafloor with the bottom phones 30 cm above the interface. Pressure time series, vertical and horizontal noise coherence (directionality), were recorded continuously for periods of 9 hours over the acoustic bandwidth of 5 Hz to 30 kHz, along with the local temperature, conductivity, and depth. An analytical Pekeris waveguide noise model was fitted to the data in order to determine the bulk sound speed, sheer speed, density, and frequency dependent attenuation in the bottom fluid half-space. Acoustic properties of the mud were determined by comparing the data to the output of a range independent noise model, featuring a ...

Technological Change and Economy in the Epipalaeolithic: Assessing the Shift from Early to Middle Epipalaeolithic at Kharaneh IV

ABSTRACTEpipalaeolithic hunter-gatherer communities in the Southern Levant exhibit numerous complex trends that suggest that the transition to the Neolithic was patchy and protracted. This paper explores the changing nature of occupation at the Epipalaeolithic site Kharaneh IV, Jordan, through an in-depth analysis of the lithic and faunal assemblages. Focusing on the analysis of a single deep sounding (unit AS42), we address how Kharaneh IV occupations link to the local landscape and environmental changes. As an aggregation site, Kharaneh IV represents an interesting locale to explore the changing nature of aggregation and social cohesion prior to the origins of agriculture, as well as changes in technology and subsistence between the Early and Middle Epipalaeolithic. We explore the tempo and nature of transition from one archaeological culture to the next through changes in technology and how this reflects the people making and using tools, to understand how foragers adapted to a changing landscape.

The measurement of muddy seabed properties using ambient noise coherence

The autonomous passive acoustic lander Deep Sound was deployed five times during the Seabed Characterization Experiment and collected ambient noise data on four hydrophones, arranged in a inverted “T” shape, with three spaced in the horizontal and two in the vertical. The lander was deployed with the bottom-most phones approximately 30 cm above the seafloor, recording over an acoustic bandwidth of 5 Hz–30 kHz. Pressure time series, vertical and horizontal noise coherence (directionality), and the local temperature and conductivity were recorded continuously for periods of 9 hours. Wind-driven surface ambient noise coherence was used to estimate bulk acoustic seabed properties. An analytical Pekeris-waveguide noise model was fitted to the data in order to determine the bulk sound speed, density, and frequency dependent attenuation in the bottom fluid half-space. [Research supported by ONR.]

Deep structure of Kamchatka according to the results of MT sounding and seismic tomography

The key features in the distribution of geoelectric and velocity heterogeneities in the Earth’s crust and the upper mantle of Kamchatka are considered according to the data of deep magnetotelluric sounding and seismotomography. Their possible origin is discussed based on the combined analysis of electric conductivity and seismic velocity anomalies. The geoelectric model contains a crustal conducting layer at a depth of 15–35 km extending along the middle part of Kamchatka. In the Central Kamchatka volcanic belt, the layer is close to the ground surface to a depth of 15–20 km, where its conductivity considerably increases. Horizontal conducting zones with a width of up to 50 km extending into the Pacific Ocean are revealed in the lithosphere of eastern Kamchatka. The large centers of current volcanism are confined to the projections of the horizontal zones. The upper mantle contains an asthenospheric conducting layer that rises from a depth of 150 km in western Kamchatka to a depth of 70–80 km beneath the zone of current volcanism. According to the seismotographic data, the low- and high-seismic-velocity anomalies of P-waves that reflect lateral stratification, which includes the crust, the rigid part of the upper mantle, the asthenospheric layer in a depth range of ~70–130 km, and a high-velocity layer confined to a seismofocal zone, are identified on the vertical and horizontal cross sections of eastern Kamchatka. The cross sections show low-velocity anomalies, which, in the majority of cases, correspond to the high-conductivity anomalies caused by the increased porosity of rocks saturated with liquid fluids. However, there are also differences that are related to the electric conductivity of rocks depending on pore channels filled with liquid fluids making throughways for electric current. The seismic velocity depends, to a great extent, on the total porosity of the rocks, which also includes isolated and dead-end channels that can be filled with liquid fluids that do not contribute to the electric-current transfer. The data on electric conductivity and seismic velocity are used to estimate the porosity of the rocks in the anomalous zones of the Earth’s crust and the upper mantle that are characterized by high electric conductivity and low seismic velocity. This estimate serves as the basis for identifying the zones of partial melting in the lithosphere and the asthenosphere feeding the active volcanoes.

Observations of Phobos by the Mars Express radar MARSIS: Description of the detection techniques and preliminary results

The Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) (Picardi et al., 2005) is a synthetic aperture low frequency radar altimeter, onboard the ESA Mars Express orbiter, launched in June 2003. It is the first and so far the only spaceborne radar that has observed the Martian moon Phobos. Radar echoes were collected on different flyby trajectories. The primary aim of sounding Phobos is to prove the feasibility of deep sounding, into its subsurface.MARSIS is optimized for deep penetration investigations and is capable of transmitting at four different bands between 1.3MHz and 5.5MHz with a 1MHz bandwidth. Unfortunately the instrument was originally designed to operate exclusively on Mars, assuming that Phobos would not be observed. Following this assumption, a protection mechanism was implemented in the hardware (HW) to maintain a minimum time separation between transmission and reception phases of the radar. This limitation does not have any impact on Mars observation but it prevented the observation of Phobos.In order to successfully operate the instrument at Phobos, a particular configuration of the MARSIS onboard software (SW) parameters, called “Range Ambiguity,” was implemented to override the HW protection zone, ensuring at the same time a high level of safety of the instrument.This paper describes the principles of MARSIS onboard processing, and the procedure through which the parameters of the processing software were tuned to observe targets below the minimum distance allowed by hardware.Some preliminary results of data analysis will be shown, with the support of radar echo simulations. A qualitative comparison between the simulated results and the actual data, does not support the detection of subsurface reflectors.

The chronostratigraphy of the Haua Fteah cave (Cyrenaica, northeast Libya) — Optical dating of early human occupation during Marine Isotope Stages 4, 5 and 6

The paper presents the results of optical dating of potassium-rich feldspar grains obtained from the Haua Fteah cave in Cyrenaica, northeast Libya, focussing on the chronology of the Deep Sounding excavated by Charles McBurney in the 1950s and re-excavated recently. Samples were also collected from a 1.25 m-deep trench (Trench S) excavated during the present project below the basal level of the Deep Sounding. Optically stimulated luminescence (OSL) data sets for multi-grain, single aliquots of quartz for samples from the Middle Trench were previously published. Re-analyses of these OSL data confirm significant variation in the dose saturation levels of the quartz signal, but allow the most robust OSL ages to be determined for comparison with previous age estimates and with those obtained in this study for potassium-rich feldspars from the Deep Sounding. The latter indicate that humans may have started to visit the cave as early as ∼150 ka ago, but that major use of the cave occurred during MIS 5, with the accumulation of the Deep Sounding sediments. Correlations between optical ages and episodes of “Pre-Aurignacian” artefact discard indicate that human use of the cave during MIS 5 was highly intermittent. The earliest phases of human activity appear to have occurred during interstadial conditions (5e and 5c), with a later phase of lithic discard associated with more stadial conditions, possibly MIS 5b. We argue that the “Pre-Aurignacian” assemblage can probably be linked with modern humans, like the succeeding “Levalloiso-Mousterian” assemblage; two modern human mandibles associated with the latter are associated with a modelled age of 73–65 ka. If this attribution is correct, then the new chronology implies that modern humans using “Pre-Aurignacian” technologies were in Cyrenaica as early as modern humans equipped with “Aterian” technologies were in the Maghreb, raising new questions about variability among lithic technologies during the initial phases of modern human dispersals into North Africa.

Reconstructing subsistence practices: taphonomic constraints and the interpretation of wild plant remains at aceramic Neolithic Chogha Golan, Iran

In this paper we discuss the plant-based subsistence economy during the formation of archaeological horizons (AH) II and I at the aceramic Neolithic site of Chogha Golan, Iran. The deposits date to between 9,800 and 9,600 cal bp. In order to reconstruct subsistence practices and their development reliably, we conducted a taphonomic analysis to identify factors that influenced the composition of the archaeobotanical assemblage. The flotation samples derive from two excavation areas in the centre of the tell, the deep sounding and area A. Using correspondence analysis, we link the biased composition of the plant remains from AH I to their relatively poor preservation. Two different sampling strategies applied in excavation area A also affected the composition of the samples. In contrast, we did not find compositional differences among the samples from AH II of both excavation areas. Our results emphasize the need for taphonomic analyses prior to interpreting the taxonomic composition of charred archaeobotanical assemblages. Considering these results, we discuss the subsistence economy of Chogha Golan. Domestic emmer wheat was cultivated from AH II onwards. Wild barley, Aegilops sp., lentils, peas and various vetches may have been cultivated as well. This spectrum of typical Neolithic food plants was supplemented by a high diversity of other potential wild food resources, including medium and small-seeded grasses, Pistacia, Bolboschoenus glaucus, Malva and Brassicaceae. A compilation of ethnobotanical data, mainly from the Near and Middle East, represents the basis for assessing the potential uses of the wild plants.

Comparative study of deep structures by means of passive microseismic sounding and seismic tomography

Modern surface wave–based approaches to the deep sounding of the Earth are compared, along with results from reconstructing deep structure of the Hawaiian plume, obtained by phase and amplitude methods. Ways of further improving these methods are proposed.

The depth dependence of ambient noise in deep ocean trenches

A series of experiments aimed at measuring the power spectrum and vertical and horizontal noise coherence (directionality) in the deep ocean were carried out between 2009and 2015 using a family of autonomous instrument platforms named “Deep Sound.” Deep Sound is a free-falling acoustic recorder designed to descend from the ocean’s surface to a pre-assigned depth where it drops an iron weight and returns to the surface under its own buoyancy, while recording pressure time series on four hydrophones with vertical and horizontal spacing over the bandwidth 5 Hz—30 kHz. The complete vertical noise profile was recorded from the surface to 6 km in the Philippine Sea, 8.5 km in the Tonga Trench, and 9 km in the Serena and Challenger Deeps in the Mariana Trench. Generally, the vertical noise coherence is well described by the Cron & Sherman surface noise model with some depth-dependence explained by seawater attenuation and local sound speed variations. Below the reciprocal or critical depth (depth at which the so...

Interwoven Strands for Refining the Chronology of the Neolithic Tell of Vinča-Belo Brdo, Serbia

AbstractA formally modeled radiocarbon chronology for a new profile through the great Neolithic tell of Vinča-Belo Brdo, Serbia, is the third interwoven strand in refining the chronology of the tell. This now joins models for the whole sequence based on the archive of early excavations, and for the last two known horizons at the top of the settlement mound, investigated in recent decades. In the new deep sounding, Vinča culture occupation from the 52nd century cal BC is slightly later than in the main sequence, probably reflecting the horizontal extension of the tell as it began to grow. The last dated occupation falls in the late 47th–early 46th century cal BC, slightly earlier than in the main sequence, but the top of the profile is affected by the slippage that caused the new excavations. Formal estimates are given for the succession and varying durations of burnt and unburnt houses, and indicate a period in the first part of the 5th millennium without house burning. Overall, the combined results from the three interwoven strands serve to produce a radically enhanced understanding of the temporality of the tell, which builds on, rather than supplants, previous research. We knew previously that Vinča-Belo Brdo was very long-lived, but now we can time that history with much greater precision. We can assert with much greater confidence that its vertical buildup was steady and largely uninterrupted. We have begun, from the work on the top of the tell and in the new deep sounding, to grasp better the fluctuations in house durations from generation to generation, and can now contrast the relative fortunes of unburnt and burnt houses. We can say much more about the timing and tempo of the ending of the tell, and about the possible circumstances in which that took place.

A passive low frequency instrument for radio wave sounding the subsurface oceans of the Jovian icy moons: An instrument concept

Exploration of subsurface oceans on Jovian icy moons is a key issue of the icy moons’ geology. Electromagnetic wave propagation is the only way to probe their icy mantles from the orbit.In the present paper, a principal concept of a passive interferometric instrument for deep sounding of the icy moons’ crust is proposed. Its working principle is measuring and correlating Jupiter's radio wave emissions with reflections from the deep sub-surface of the icy moons. A number of the functional aspects of the proposed experiment are studied, in particular, impact of the wave scattering on the surface terrain on the instrument performance and digital sampling of the noisy signal. Results of the test of the laboratory prototype of the instrument are also presented in the paper.

Study of interaction of ELF–ULF range (0.1–200 Hz) electromagnetic waves with the earth’s crust and the ionosphere in the field of industrial power transmission lines (FENICS experiment)

This article is devoted to describing the theory, technique, and first experimental results of a control source electromagnetic (CSEM) study of the Earth’s crust and ionosphere with the use of two mutually orthogonal industrial transmission lines 109 and 120 km in length in the frame of FENICS (Fennoscandian Electrical Conductivity from Natural and Induction Control Source Soundings) experiment. The main part of the measurements is executed on the territory of the Fennoscandian shield at distances from the first hundreds kilometers up to 856 km from the source with the purpose of the deep electromagnetic sounding of the Earth’s crust and upper mantle. According to the results of these studies clarifying the parameters of “normal” (standard) geoelectric section of the lithosphere to a depth of 60–70 km, the anisotropy parameters are evaluated and a geothermal and rheological interpretation in conjunction with the analysis of the seismic data is executed. Furthermore, to study the propagation of ELF–LLF waves (0.1–200 Hz) in an “Earth–Ionosphere” waveguide, the measurements are carried out apart from Fennoscandian shield at distances up to 5600 km from the source (in Ukraine, Spitsbergen, Poland, Kamchatka, and other areas). According to the results of these studies, the experimental estimates of the influence of the ionosphere and of the displacement currents on the propagation of ELF–ULF waves in the upper half-space at the different azimuths generation of the primary field are obtained.

Conductivity Anomalies in Central Europe

This paper is a review of studies which, by applying the magnetotelluric, geomagnetic deep sounding, and magnetovariational sounding methods (the latter refers to usage of the horizontal magnetic tensor), investigate Central Europe for zones of enhanced electrical conductivity. The study areas comprise the region of the Trans-European Suture Zone (i.e. the south Baltic region and Poland), the North German Basin, the German and Czech Variscides, the Pannonian Basin (Hungary), and the Polish, Slovakian, Ukrainian, and Romanian Carpathians. This part of the world is well investigated in terms of data coverage and of the density of published studies, whereas the certainty that the results lead to comprehensive interpretations varies within the reviewed literature. A comparison of spatially coincident or adjacent studies reveals the important role that the data coverage of a distinct conductivity anomaly plays for the consistency of results. The encountered conductivity anomalies are understood as linked to basin sediments, asthenospheric upwelling, large differences in lithospheric age, and—this concerns most of them, which all concentrate in the middle crust—tectonic boundaries that developed during all mountain building phases that have taken place on the continent.

Improving of electrical channels for magnetotelluric sounding instrumentation

Abstract. The study of the deep structure of the Earth's crust is of great interest for both applied (e.g. mineral exploration) and scientific research. For this the electromagnetic (EM) studies which enable one to construct the distribution of electrical conductivity in the Earth's crust are of great use. The most common method of EM exploration is magnetotelluric sounding (MT). This passive method of research uses a wide range of natural geomagnetic variations as a powerful source of electromagnetic induction in the Earth, producing telluric current variations there. It includes the measurements of variations of natural electric and magnetic fields in orthogonal directions at the surface of the Earth. By this, the measurements of electric fields are much more complicated metrological processes, and, namely, they limit the precision of MT prospecting. This is especially complicated at deep sounding when measurements of long periods are of interest. The increase in the accuracy of the electric field measurement can significantly improve the quality of MT data. Because of this, the development of a new version of an instrument for the measurements of electric fields at MT – both electric field sensors and the electrometer – with higher levels relative to the known instrument parameter level – was initiated. The paper deals with the peculiarities of this development and the results of experimental tests of the new sensors and electrometers included as a unit in the long-period magnetotelluric station LEMI-420 are given.

Optimization of the Antennas of the EISS Radar Designed to Perform Deep Martian Subsurface Sounding

The Electromagnetic Investigation of SubSurface (EISS) instrument has been designed to get information on the morphology and geological structure of the Martian subsurface and search for potential liquid water reservoirs. EISS is an impulse radar operating from the Martian surface at central frequencies of a few megahertz in order to perform deep sounding of the subsurface. Particular attention has been paid to the design of the instrument's electrical antennas that need to transmit and receive the electromagnetic waves without distortion over the instrument's full frequency bandwidth (i.e, from 1 to 7 MHz). To fit into the mass and volume allocation, wire antennas made of identical loaded dipoles have been selected; they will be deployed on the surface by a mechanical mortarlike device. The resistive profile along the monopoles needs to be carefully chosen to ensure a proper behavior of the antenna once they are deployed on the surface. This paper deals with the performance of these electrical antennas and the optimization of their resistive profile. The study of the impact of the subsurface is performed on simulated data obtained by a numerical finite difference in time domain code. When available, experimental data show the good agreement with the theory. The studies performed show that a slightly suboptimal resistive profile will allow a correct operation of the instrument at the surface of Mars for any landing site.

Density modeling of magmatic structures in the promising Kolpakova Nickeliferous district (Median massif, Kamchatka)

The deep structure is modeled for the crustal block in the Kolpakova River basin of the Kamchatka Peninsula. A technique for developing the 3D density model on the basis of the data derived from interpretation of gravity anomalies is described. The model is used for outlining the position and shape of the massive bodies in the upper crust, which are identified with intrusions of the Dukuk nickeliferous magmatic complex, with identification of areas promising with respect to metal deposits genetically associated with intrusive mafic and ultramafic magmatism. It is shown that the proposed technique represents an effective tool for the study of the inner structure in regions poorly studied by deep geophysical sounding methods or as yet completely lacking such data.