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Rare earth elements (REEs) are widely distributed in low concentrations in all parts of the biosphere. REEs are not at all rare, their concentration in the earth's crust is close to 0.015%. REEs include the elements scandium, yttrium and the lanthanides from lanthanum to lutetium. REEs show similar physical and chemical properties. Today REEs are applied in industries and technologies, in agriculture as microfertilizers and feed additives and they are also used in medicine. REEs are dispersed especially as accessory minerals in pegmatites, granites and associated metamorphic volcanic rocks. Out of more than 250 kinds of minerals containing REEs, only bastnaesite and monazite are of economic importance. Their concentration in the soil varies widely and depends on their presence in parental materials, soil texture, organic matter content, pedogenetic processes and anthropogenic activities. REEs are found in small concentrations in surface stagnant and flowing waters as well as in underground waters. They are found in water in both suspended and dissolved form. REEs enter the atmosphere from various sources, largely owing to human activities. The majority of REEs in the atmosphere are carried by microscopic particles. The uptake and consequently accumulation of REEs in plants are affected by numerous biotic factors, such as plant species and genotype, and abiotic factors such as their concentration in the soil and some chemical and physical soil characteristics. They can enter plants via both root and foliage tissues. There are plant species called hyperaccumulators that are able to accumulate significant amounts of REEs without adverse consequences. RREs are not biogenic for higher plants or for other living organisms, but can influence their life processes. Experiments show that REEs can be beneficial for growth, yield and biochemical composition of cultivated plants. They can also alleviate some ecological stress in plants. It is not clear enough how they affect human and animal health. The wide-spread application of REEs in different industries as well as in agriculture lead to a constant increase of the concentrations of these elements in the environment. Therefore, studies on the uptake, accumulation, distribution of REEs in cultivated plant species and their entrance into the food chain as well as their stimulating or toxic effect on living organisms, can be very significant in the future. [ABSTRACT FROM AUTHOR]

Since the start of the 21st century, the widespread application of ion probes has promoted the mass output of high-precision and high-accuracy U–Th–Pb geochronological data. Zircon, as a commonly used mineral for U–Th–Pb dating, widely exists in the continental crust and records a variety of geological activities. Due to the universality and stability of zircon and the long half-lives of U and Th isotopes, zircon U–Th–Pb geochronology can provide nearly continuous records for almost the entirety of Earth's history and is thus essential to studying the growth and evolution of the continental crust and Earth system evolution. Here, we present a database of zircon U–Th–Pb geochronology that samples the global continental crust and spans nearly all of Earth's history. This database collects ∼2 000 000 geochronology records from ∼12 000 papers and dissertations. This paper describes the compiled raw data, presents the relationship between dating error and zircon age, compares the error levels of different dating instruments, and discusses the impact of sampling bias on data analysis as well as how to evaluate and minimize this impact. In addition, we provide an overview of the temporal and spatial distribution of global zircon ages and provide key insights into the potential research value of zircon ages for Earth system science, such as crustal evolution, plate tectonics, and paleoclimate changes, as well as commercial use in mining and energy exploration. Overall, this data collection provides us with a comprehensive platform with which to study zircon chronological data in deep time and space. The described zircon database is freely available via Zenodo at 10.5281/zenodo.7387566 (Wu et al., 2023). [ABSTRACT FROM AUTHOR]

In this paper, the derivation of a concise closed form for the gravitational field of a polyhedron is presented. This formula forms the basis of the algorithm for calculating the gravitational field of an arbitrary shape body with high accuracy. Based on this algorithm, a method for gravity data inversion (creating density models of the Earth's crust) has been developed. The algorithm can accept either regular or irregular polyhedron discretization for density model creation. The models are approximated with dense irregular grids, elements of which are polyhedrons. When performing gravity data inversion, we face three problems: topography with large amplitude, the sphericity of the planet, and a long computation time because of the large amount of data. In our previous works, we have already considered those problems separately but without explaining the details of the computation of the closed-form solution for a polyhedron. In this paper, we present for the first time a performance-effective numerical method for the inversion of gravity data based on topography. The method is based on closed-form expression for the gravity field of a spherical density model of the Earth's crust with the upper topography layer, and provides great accuracy and speed of calculation. There are no restrictions on the model's geometry or gravity data grid. As a case study, a spherical density model of the Earth's crust of the Urals is created. [ABSTRACT FROM AUTHOR]

This paper analyzes and reviews the rapid uplifts of the Earth's crust in the Caucasus that occurred over the last century. The uplifts were registered by precise repeated state leveling and reflected on officially published maps of vertical movements of the Earth's crust. This study summarizes information on the region's vertical movements over more than a century. The present study describes the technology for creating maps of recent vertical movements of the Earth's crust using precision leveling data. This paper summarizes cases of recording uplifts of the Earth's surface in other regions of the world in connection with seismic activity. The authors carried out intercomparison of vertical movements with tectonics, seismicity, and geophysical fields, which discovered their apparent mutual correspondence. This indicates the deep tectonic nature of the observed uplifts of the Earth's crust. Spatial and temporal agreement with the distribution of strong earthquakes showed a natural relationship. It has been shown that strong earthquakes are confined to the boundaries of zones of rapid uplift. They occur predominantly in areas of transition between uplifts and subsidence. The results obtained demonstrate the role of the study and observations of vertical movements of the Caucasus in assessing periods and areas of increased seismic hazard. [ABSTRACT FROM AUTHOR]

This document is an editorial from the journal "Contributions to Mineralogy & Petrology." It announces changes in the journal's editorial board, including the retirement of Prof. Tim Grove as the Executive Editor and the appointment of Prof. Dante Canil as the new Executive Editor. It also mentions the stepping down of Profs Mark Ghiorso and Timm John as Associate Editors and the addition of Christy Till and Ralf Dohmen as new Associate Editors. The editorial encourages the community to continue submitting articles that contribute to our understanding of the Earth's crust, mantle, and core. The document also highlights the high scientific quality of papers published in the journal, with an average of 61.7 citations per article. [Extracted from the article]

Geoparks are unique geographical areas whose geological significance is worthy of UNESCO designation as a Global Geopark. As of 2022, 177 geoparks located in 46 countries have this designation. The aim of this paper is to identify and analyse the worldwide scientific production published in the Web of Sciences database in the context of Geoparks. The methodology used was bibliometric analysis, which allows for the rigorous exploration and analysis of large volumes of data. To this end, descriptive and relational indicators were obtained for the field of study; performance analysis, scientific mapping, and network analysis. A total of 324 articles were identified, the first of which was from 1999 by Wolfgang Eder, in which he presented the UNESCO initiative on the creation of geoparks as a tool to promote a better understanding of the geological heritage and the rational use of the Earth's crust; the rest of the articles were written after the programme was launched (2001). Few authors work on the subject continuously, the author with the highest number of publications has six, and most of the authors with a single authorship are transient. The countries with the highest number of publications are China, followed by Spain, Portugal, Brazil and Italy, where scientific production is concentrated; the high rate of transience indicates that many countries have only one publication. Most publications are concentrated in two journals: geoheritage and geosciences. In the early years (1999–2003), publications were associated with two research areas, geology and palaeontology, and it is in the last five years (2019–2002) that the areas of knowledge showing interest in the subject have diversified. [ABSTRACT FROM AUTHOR]

It is known that the source of a tectonic earthquake in the framework of the theory of elasticity and viscoelasticity is considered to be displacement along a certain fault surface. Usually, when describing a source, the geometry of the fault surface is simplified to a flat rectangular area. The displacement vector is assumed to be constant. In this paper, we propose a model of an earthquake source in the form of a displacement with a constant vector along a stochastic uneven surface. A number of standard assumptions are made during the modeling. We take into account only the elastic properties of the medium. We consider the Earth's crust as a half-space and assume that the medium is homogeneous and isotropic. For the mathematical description of the earthquake source, we use the classical force equivalent of displacement along the fault. This is the distribution of double pairs of forces. The field of displacements under the action of body forces is found through a combination of Mindlin nuclei of strain. The paper presents numerical analytic solutions for displacement along the strike-slip fault corresponding to one of an earthquake source mechanism. We propose to introduce a random deformation of a rectangular flat fault surface. The paper shows the results of a computational experiment comparing the levels and regions of relative deformations of the Earth's crust in the case of displacement along a flat fault surface and along a stochastic uneven one. In the case of a stochastic fault surface, the regions of relative deformations become asymmetric. Such differences from the classical case can be useful for an explanation as to why in some cases the simulation results differ from the results of observations. [ABSTRACT FROM AUTHOR]

Beryllium, the 44th most abundant element in the Earth's crust, is found ubiquitously in environmental matrices, including air, soil, and water, as well as in a variety of food items such as grains, fruits, and vegetables. The typical concentration of Be in air is reported to be ~0.05 ng/m3, whereas in soil, its concentration varies from ~2 to 5 ppm. The prevalence of Be in soil leads to its presence in water as well as in plants, and various human activities such as burning of coal, petrol, diesel, mining, and other industrial activities may further increase the concentration of beryllium in environment and associated matrices. It needs to be mentioned that the typical concentration of Be in food items is of the order of few ppb, whereas in drinking water, the typical values are reported to be <1 ppb or so. Based on the literature survey including some of the most recent studies, the present paper provides summary on concentration of Be in air, soil, and other relevant matrices as concise and consolidated reports on beryllium are scarce. In addition, related information like Be in drinking water along with available guidelines is also provided. Information on the prevalence of other isotopes of beryllium, i.e., 7Be4 and 10Be4, which are radioactive and are produced by cosmic rays in atmosphere, is also included in the present paper. [ABSTRACT FROM AUTHOR]

Magmatism is a very important manifestation of the deep activity of the Earth. The geochronology and geochemistry of the Zhaojinggou monzogranite pluton indicate that magmas were derived from the late Paleoproterozoic to Mesoproterozoic lower crustal mafic materials. It was established a magma plumbing system that provides new constraints for magma evolution. [Extracted from the article]

Numerous studies have been carried out on the community structure and diversity of biological soil crusts (BSCs) as well as their important functions on ecosystem processes. However, the amount of BSC-derived organic carbon (OC) input into soils and its chemical composition under natural conditions has rarely been investigated. In this study, different development stages of algae- and moss-dominated BSCs were investigated on a natural (< 17yr old BSCs) and experimental sand dune (< 4yr old BSCs) in northeastern Germany. We determined the OC accumulation in BSC-layers and the BSC-derived OC input into the underlying substrates for bulk materials and fractions < 63µm. The chemical composition of OC was characterized by applying solid-state 13C NMR spectroscopy and analysis of the carbohydrate-C signature. 14C contents were used to assess the origin and dynamic of OC in BSCs and underlying substrates. Our results indicated a rapid BSC establishment and development from algae- to moss-dominated BSCs within only 4 yr under this temperate climate. The distribution of BSC types was presumably controlled by the surface stability according to the position in the slope. We found no evidence that soil properties influenced the BSC distribution on both sand dunes. 14C contents clearly indicated the existence of two OC pools in BSCs and substrates, recent BSC-derived OC and lignite-derived "old" OC (biologically refractory). The input of recent BSC-derived OC strongly decreased the mean residence time of total OC. The downward translocation of OC into the underlying substrates was only found for moss-dominated BSCs at the natural sand dune which may accelerate soil formation at these spots. BSC-derived OC mainly comprised O-alkyl C (carbohydrate-C) and to a lesser extent also alkyl C and N-alkyl C in varying compositions. Accumulation of alkyl C was only detected in BSCs at the experimental dune which may induce a lower water solubility of BSC-derived extracellular polymeric substances when compared to BSCs at the natural sand dune indicating that hydrological effects of BSCs on soils depend on the chemical composition of the extracellular polymeric substances. [ABSTRACT FROM AUTHOR]

Gallium and indium are crucial metals in various industries, such as the medical and telecommunication industries. They can find applications as pure metals, alloys and alloy admixtures, oxides, organometallic compounds, and compounds with elements such as nitrogen or arsenic. Recovery of these two metals from waste is an important issue for two main reasons. First, gallium and indium are scattered in the Earth's crust and their minerals are too rare to serve as a primary source. Second, e-waste contributes to the rapidly growing problem of Earth littering, as its amount increased significantly in recent years. Therefore, it is essential to develop and implement procedures that will enable the recovery of valuable elements from waste and limit the emission of harmful substances into the environment. This paper discusses technological operations and methods that are currently used or may be used to produce pure gallium and indium or their oxides from waste. The first step was described—waste pretreatment, including disassembly and sorting in several stages. Then, mechanical treatment as well as physical, chemical, and physicochemical separations were discussed. The greatest emphasis was placed on the hydrometallurgical methods of gallium and indium recovery, to be more precise on the extraction and various sorption methods following the leaching stage. Methods of obtaining pure metals or metal oxides and their refining processes were also mentioned. [ABSTRACT FROM AUTHOR]

The Nanling region is located at the intersection of the Yangtze Block and Cathaysia Block and is characterized by complex geological and tectonic processes, as well as distinct W-Sn-REE mineralization. Despite extensive research on the mineralization of W-Sn and REE deposits in the Nanling region, the factors impacting the distribution pattern of eastern tungsten and western tin deposits, as well as the mechanism of REE enrichment in the parent rocks, remain uncertain. Deep structural and tectonic variability plays a crucial role in the formation of mineral deposits in the upper crust. Information on deep structural and tectonic variability is contained in the Moho depth, Curie depth, effective elastic thickness, lithospheric density, and thermal structure derived from the processing and inversion of satellite gravity and magnetic data. In this paper, we comprehensively analyse satellite gravity and magnetic data from the Nanling region, integrating the processing and inversion results with the tectonic evolution of this region and relevant geological information. It is hypothesized that the Chenzhou–Linwu fault serves as a channel for mineral and thermal transfer in the Sn ore aggregation zone, facilitating the material transport from the deep mantle to the surface and ultimately leading to the formation of Sn-enriched granite. The collection area of tungsten ore is more weakly associated with the Chenzhou–Linwu fault, and through deep heat transfer, tungsten components are primarily concentrated in the Earth's crust to produce W-enriched granite. The primary source of REE enrichment in the parent rocks associated with REE mineralization is predominantly derived from the felsic crust, and the rapid intrusion of deep magma resulting from the subduction and retraction of the Palaeo-Pacific Plate is a contributing factor to the contrasting enrichment of light and heavy rare-earth elements. Mineral crystalline differentiation is relatively high, leading to the formation of ore-forming parent rocks with high heavy rare-earth element contents. [ABSTRACT FROM AUTHOR]

Lavas erupted in Continental Flood Basalt (CFB) provinces are not primary magmas; they are differentiated products that result from large volumes of melt migrating and stalling in the lithosphere prior to eruption, resulting in complex liquid lines of descent. Geochemical models can be used to constrain the various influencers of magma differentiation (recharge, assimilation, fractional crystallization (FC), eruption, and mixing). Temporal constraints for changes in plumbing system dynamics are recorded in the petrography and stratigraphy of the erupted lava flows. This study focuses on the flow‐stratigraphy preserved within the Oligocene Ethiopian low‐Ti flood basalt province, located on the NW Ethiopian Plateau. We present new bulk rock geochemistry from 107 lavas and interpret these data within a petrostratigraphic framework. Our model results suggest that both a deep (∼0.6 GPa) and shallow (<0.2 GPa) magmatic system are active throughout the main phase of volcanism. Our recharge evacuation assimilation and fractional crystallization models (REAFC) show that during the main phase of magmatism evacuation from both the deep (65%) and shallow (55%) systems reached an apex. During the terminal phases, magma evacuation from the deeper system ceases while evacuation from the shallow system is much reduced (25%). The degree of crustal contamination predicted by REAFC (4%–10%) is lower than previous estimates determined for this region using assimilation with FC only models (12%–25%). Our study highlights the importance of evaluating petrography while interpreting geochemical models in CFB. Plain Language Summary: Large eruptions of lava known as "flood basalts" have occurred several times in Earth's history. These eruptions have been linked to changes in Earth's climate, mass extinctions, the dawn of human civilization, and the splitting of large continents. Despite the impact these eruptions have, there is little understood about the journey of magma to the surface. As magma travels through Earth's crust, it changes physically and chemically. Consequently, each lava flow erupted is a record of these changes. There are multiple paths that magma can take to the surface, each leaves a unique signature on the lava. If we think of each lava flow as pages in a book, and groups of lava flows as chapters in a novel, then we can begin to tell the story of how some of the largest eruptions on Earth changed the world. In this paper, we explore one of the youngest and most complete sequences on flood basalt lavas on Earth, the Ethiopian Flood Basalt Province. We use physical and chemical signatures to identify and model key changes in eruption behavior. The results show how magma becomes shallower, and the volume of magma increasing and then decreasing over time. Key Points: Combining petrographic and geochemical datasets yields a more complete picture of changes in magmatic flux in a continental flood basalt provinceRecharge‐evacuation models indicate lower crustal contribution for the Ethiopian Flood Basalt province than previously suggestedSeveral geochemical trends in the Ethiopian low‐Ti province can be explained using recharge‐evacuation‐assimilation‐fractional crystallization models [ABSTRACT FROM AUTHOR]

This paper is focused on the problems of studying the thermal conditions of the Earth's crust in the transition zone from the Baltic Shield to the Barents Sea Plate, based on temperature measurements in the deep well P-1 located on the isthmus between the Srednii and Rybachii peninsulas (northeast of the Baltic Shield). A brief description of the comprehensive geophysical studies on the wellbore is given. The measurements of thermal conductivity and the concentration of radiogenic elements in borehole core rock samples are reported. The role of hydrogeological conditions has been proved to be minor in the temperature field disturbance in the well. Horner's method has been used to calculate undisturbed temperatures at the bottoms of drilling intervals and to estimate the geothermal gradient of the Archean horizons in the section where the heat flow is estimated at 32 mW/m2. The undisturbed heat flow is estimated at 20 mW/m2 for the Riphean complex of the section. The study results characterize the thermal conditions of the Earth's crust in the transition zone from the Baltic Shield to the Barents Sea Plate. [ABSTRACT FROM AUTHOR]

The study area is the city of Zintan, in northwestern Libya, which has grown over the past 30 years. Its current population is roughly 30,000. Although the city is in part commercial, most of the population engages in agriculture and primarily grows cereal crops (wheat and barley). The demand of the growing city for agricultural products has increased, intensifying the use of fertilizers, pesticides, and insecticides. Consequently, concentrations of potentially toxic elements (PTE) in the soil have increased. To assess the soil quality (to provide a snapshot of the condition of the soil), systematic sampling was undertaken across a grid of about 2 km × 2 km. The main objective was to determine the chemical and mineral composition of the area of interest, keeping in mind the geological footprint of the terrain. The geologic framework itself is not conducive to elevated concentrations of elements like U, Th, Mo, As, Hg, Pb, and Cr. Therefore, metal concentrations greater than the amounts in the Earth's crust are most likely of anthropogenic origin. A total of 143 samples were collected and chemical analyses were performed using a Thermo Fisher Scientific Niton XL3t GOLDD+ XRF analyzer for the following elements: Mo, Zr, Sr, U, Rb, Th, Pb, Au, Se, As, Hg, Zn, W, Cu, Ni, Co, Fe, Mn, Cr, V, Ti, Sc, Ca, K, S, Ba, Cs, Te, Sb, Sn, Cd, Pd, and Ag. This paper provides examples of elevated concentrations, potentially harmful to the environment, such as those of the following: sulfur of unknown origin (two to three times higher than the Earth's crust average); arsenic, given that there are no related natural phenomena (all the samples measured displayed concentrations higher than those found in the Earth's crust); mercury (concentrations much higher than permissible levels); cesium (additional investigations required to determine the origin); molybdenum; and uranium likely resulting from the use of superphosphates (concentrations nearly always significantly higher than those in the Earth's crust). [ABSTRACT FROM AUTHOR]

With the increasing exploitation of mineral resources by humans, exploring non-traditional areas for hidden resources such as deep earth and sediment-covered regions has become a significant challenge in the field of mineral exploration. Geochemical data, as a crucial information carrier of geological bodies, serves as one of the direct and effective sources for quantitative analysis of regional geological evolution and mineralization prediction studies. It plays an indispensable role in geographic information system (GIS)-based mineral exploration. Due to the neglect of spatial distribution characteristics and the variability of statistical features with spatial metrics in traditional statistical methods, this paper employs fractal/multifractal and the local singularity analysis to identify geochemical anomalies from background and characterize geochemical distributions associated with porphyry Cu-Au mineralization in the Duolong mineral district, Tibet, China. A novel algorithm for estimating the singularity index, which takes anisotropy into consideration, is proposed and practically applied to the Duolong district. By comparing with the isotropic singularity index, this new method objectively identifies anisotropic geochemical signatures and investigates non-linear behaviors of ore-forming elements, making it more practical and effective in geo-anomaly extraction. Furthermore, the current method is capable of indicating variations in geochemical distributions at different scales through directional arrows marking analytical windows. The summed-up direction of these multi-scale vectors effectively demonstrates migration trends of ore materials at each location within the study area. The new method can pinpoint the location of ore-forming element accumulation and migration directions, unlocking valuable insights from complex datasets. This promises to revolutionize our understanding of how minerals are formed and distributed within the Earth's crust. [ABSTRACT FROM AUTHOR]

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Large-scale layered intrusions of a peridotite–pyroxenite–gabbronorite complex, to which Cr, Ni, Cu, and PGE deposits and ore occurrences are confined, were emplaced into the Baltic paleocontinent 2.50–2.45 Ga. Layered intrusions in the Monchegorsk Ore District, including the Monchepluton and Imandra–Umbarechka Complex, as well as the gabbro-anorthosite complex of the Main Ridge, were analyzed earlier geochemically and isotopically. In the present paper, the authors analyze layered intrusions in the Kola region (Mount Generalskaya) and Karelia (Kivakka, Kovdozero, and the Burakovsky Pluton). The primary composition of mantle magmas for the layered intrusions is assumed to be identical to that of the komatiitic basalts making up the volcanogenic units of the Vetreny Belt and the Imandra–Varzuga zone. A general model for the formation of layered intrusions includes superplume uplift in the early Paleoproterozoic, the generation of mantle magmas and their injection into the lower portion of the earth crust, the formation of deep-seated and intermediate magma chambers, and the intense contamination of the granulite–metamorphic complex followed by the generation of magma chambers provoked by single or multiple injections. [ABSTRACT FROM AUTHOR]

Since the start of the 21st century, the widespread application of ion probes has promoted the mass output of highprecision and high-accuracy U‒Th‒Pb geochronology data. Zircon, as a commonly used mineral for U‒Th‒Pb dating, widely exists in the continental crust and records a variety of geological activities. Due to the universality and stability of zircons and the long half-lives of U and Th isotopes, zircon U‒Th‒Pb geochronology can provide nearly continuous records for almost the entire history of Earth and is thus essential to studying the growth and evolution of the continental crust and even Earth system evolution. Here, we present a database of zircon U‒Th‒Pb geochronology that samples the global continental crust and spans nearly all of Earth's history. This database collects ~2,000,000 geochronology records from ~12,000 papers and theses and is by far the largest geochronology database to our knowledge. This paper describes the complied raw data, presents the relationship between dating error and zircon age, compares the error levels of different dating methods, and discusses the impact of sampling bias on data analysis as well as how to evaluate and weaken this impact. In addition, we provide an overview of the temporal and spatial distribution of global zircon ages and provide key insights into the potential research value of zircon ages for Earth system science, such as crustal evolution, supercontinent cycles, plate tectonics, paleoclimate changes, biological extinction, as well as commercial use in mining and energy. Overall, this collection not only provides us with a comprehensive platform with which to study zircon chronological data in deep time and space but also makes it possible to explore the underlying geodynamic mechanisms and evolution of Earth's system and its astronomical environment. [ABSTRACT FROM AUTHOR]

Shortly thereafter, in the wake of the "plate tectonics revolution" and working with Alan White, Ross noted the striking similarity between the average composition of the continental crust and andesite - one of the most diagnostic igneous rock types formed in subduction zones (Taylor & White, 1965). Stuart Ross Taylor, always known by his middle name Ross, was born in Ashburton, New Zealand, on November 26, 1925, and died peacefully in Canberra, Australia, on May 23, 2021, at the age of 95, surrounded by his wonderful and loving family. Brian was Goldschmidt's last student in Oslo (but finished his own Ph.D. in Stockholm due to the invasion of Norway) and Ross was always proud of the direct academic lineage to Goldschmidt (as are Ross's students and their students). In 2006, he led the famous Taylor Clan (Ross - Father; Larry - Son; Jeff - Holy Ghost) in an important paper: I The Moon: A Taylor perspective i (informally called Taylor-cubed). [Extracted from the article]

In this paper, we analyzed the results of experimental data processing in the study of regularities of propagation and transformation of low-frequency harmonic signals at the boundary of the "sea−land−sea" system. Harmonic signals at a carrier frequency of 33 Hz were generated by a low-frequency hydroacoustic radiator in Vityaz Bay. Then, they passed along the shelf of decreasing depth, transformed into seismoacoustic signals of the upper layer of the Earth's crust and the bedrocks of Shultz Cape and excited hydroacoustic signals at the corresponding frequency in the shelf waters in the open part of the Sea of Japan. When processing the experiment results, we obtained the vertical distributions of the pressure field, caused by an acoustic low-frequency signal passing through the upper layer of the Earth's crust. We presented the distributions of hydroacoustic and seismoacoustic energies. The obtained experimental data were compared with the simulations by the model, developed strictly according to the experiment scheme and the geological structure of the area. In the discussion of the obtained results, we explained a probable mechanism of acoustic energy propagation and the nature of the vertical distributions of the pressure field formation. [ABSTRACT FROM AUTHOR]

The advent of novel technologies revealed that other geophysical signals than those directly related to fault motion could be used to probe the state of deformation of the Earth's crust. Electromagnetic signals belonging to this category have been increasingly investigated in the last decade in association to natural earthquakes and laboratory rock fractures. These studies are hampered by the lack of continuous recordings and a systematic mathematical processing of large data sets. Indeed, electromagnetic signals exhibit characteristic patterns on a specific frequency band (the very low frequency, VLF) that correlate uniquely with the paroxistic rupture of rocks specimens under uniaxial laboratory tests and were also detected in the atmosphere, in association to moderate magnitude earthquakes. The similarity of laboratory and atmospheric VLF offers an unique opportunity to study the relation between VLF and rock deformation on at least two different scales and to enlarge the dataset by combining laboratory and atmospheric data. In this paper we show that the enlarged VLF dataset can be successfully used, with a neural network approach based on LSTM neural networks to investigate the potential of the VLF spectrum in classifying rock rupture precursors both in nature and in the laboratory. The proposed approach lays foundation to the automatic detection of interesting VLF patterns for monitoring deformations in the seismically active Earth's crust. [ABSTRACT FROM AUTHOR]

Granite is a distinctive constituent part of the continental crust on Earth, the formation and evolution of which have long been hot research topics. In this paper, we reviewed the partial melting processes of crustal rocks without or with fluid assistance and summarized the role of fluids and volatiles involved in the formation of granitic melts. As a conventional model, granitoids were thought to be derived from the dehydration melting of hydrous minerals in crustal basement metamorphic rocks in the absence of external fluids. However, the external-fluid-assisted melting of crustal metamorphic rocks has recently been proposed to produce granitoids as extensive fluids could be active in the deep continental crust, especially in the subduction zones. It has been demonstrated experimentally that H2O plays a crucial role in the partial melting of crustal rocks, in which H2O can (1) significantly lower the solidus temperature of the melted rocks to facilitate partial melting; (2) affect the melting reaction process, mineral stability, and the composition of melt; and (3) help the melt to separate more easily from the source area and aggregate to form a large-scale magma chamber. More importantly, dissolved volatiles and salts in the crustal fluids could also lower the solidus temperature of rocks, affect the partitioning behaviors of trace elements between minerals and melts, and facilitate the formation of some distinctive granitoids (e.g., B-rich, F-rich, and high-K granitoids). Furthermore, various volatiles dissolved in fluids could result in elemental or isotopic fractionation as well as the diversity of mineralization during fluid-assisted melting. In-depth studies regarding the fluid-assisted partial melting of crustal rocks will facilitate a more comprehensive understanding of melting of the Earth's crust, thus providing strong theoretical constraints on the genesis and mineralization of granitoids as well as the formation and evolution of the continental crust. [ABSTRACT FROM AUTHOR]

The first results of experimental registration of slow deformation waves in the Earth's crust in connection with the evolution of seismicity at the interface between tectonic plates are presented. The initial data were the time series of changes in the coordinates of continuous GNSS observation stations, earthquake catalogs, and digital maps of the fault tectonics of the region. This paper uses the strategy developed by the authors for creating kinematic visualizations of the seismic-deformation process. Heuristic analysis of the obtained video images made it possibële to detect the phenomena of slow migration of deformations of the Earth's crust, i.e., deformation waves due to the seismic process and the triggering of strong earthquakes on time intervals of 11 to 15 years. [ABSTRACT FROM AUTHOR]

Postglacial land uplift is a complex process related to the continental ice retreat that took place about 10 000 years ago and thus started the viscoelastic response of the Earth's crust to rebound back to its equilibrium state. To empirically model the land uplift process based on past behaviour of shoreline displacement, data points of known spatial location, elevation and dating are needed. Such data can be obtained by studying the isolation of lakes and mires from the sea. Archaeological data on human settlements (i.e. human remains, fireplaces etc.) are also very useful as the settlements were indeed situated on dry land and were often located close to the coast. This information can be used to validate and update the postglacial land uplift model. In this paper, a collection of data underlying empirical land uplift modelling in Fennoscandia is presented. The data set is available at 10.1594/PANGAEA.905352. [ABSTRACT FROM AUTHOR]

Volcanic activities in the Izu‐Bonin‐Mariana (IBM) oceanic arc and the Northeast Japan (NEJ) continental arc are different in spite of rather constant subduction rates of the same Pacific plate. IBM volcanoes are much more voluminous than NEJ volcanoes; IBM magmas are predominantly basaltic whereas NEJ magmas are andesitic. We propose that the crustal density structures play a key role in those differences. The crustal density structures were estimated based on seismic P‐wave velocity structure and thermodynamic calculation, suggesting that the neutral buoyancy level of a primitive, mantle‐derived basalt, where a magma chamber forms, is shallower in the IBM arc than the NEJ arc. If a magma that differentiates and attains water oversaturation could erupt at the surface, a larger amount of crystallization should occur for the magma in a deeper chamber. This idea explains that erupting magma in the IBM arc is more voluminous and more mafic than those in the NEJ magma. Plain Language Summary: This paper is concerned with mechanisms governing volcano size and lava composition. Features of volcanoes on the two arcs in Japan, the Izu‐Bonin‐Mariana (IBM) and the Northeast Japan (NEJ), are clearly different although the volcanic activities are caused by subduction of the same Pacific plate. Volcanoes on IBM are much more voluminous and mostly consist of less silica lava than those on NEJ. We propose that the density of Earth's crust plays a key role in those differences. Generally, a magma forms a reservoir at a level where the magma is equal to the crust in density and then partially solidifies there by cooling. As solidification proceeds, the rest of the magma decreases in volume and increases in silica component. Considering gas features dissolved in magma, the magma in a shallower reservoir can bubble by less solidification and erupt to the surface. Our estimation of crust densities on the two arcs indicates that the reservoir level in IBM is shallower than that in NEJ. Namely, erupting magmas in IBM are affected by less solidification and hence are more voluminous and have less silica component than those in NEJ. Key Points: Two arcs in Japan have different volcanic activities: one has voluminous, basaltic volcanoes and the other small, andesiticWe propose that the crustal density structures and hence magma chamber levels cause the differences on the volcanoesIn a shallower chamber, a magma can be saturated in water with less differentiation and erupt as voluminous, basaltic magma [ABSTRACT FROM AUTHOR]

Geodynamic modelling provides a powerful tool to investigate processes in the Earth's crust, mantle, and core that are not directly observable. However, numerical models are inherently subject to the assumptions and simplifications on which they are based. In order to use and review numerical modelling studies appropriately, one needs to be aware of the limitations of geodynamic modelling as well as its advantages. Here, we present a comprehensive yet concise overview of the geodynamic modelling process applied to the solid Earth from the choice of governing equations to numerical methods, model setup, model interpretation, and the eventual communication of the model results. We highlight best practices and discuss their implementations including code verification, model validation, internal consistency checks, and software and data management. Thus, with this perspective, we encourage high-quality modelling studies, fair external interpretation, and sensible use of published work. We provide ample examples, from lithosphere and mantle dynamics specifically, and point out synergies with related fields such as seismology, tectonophysics, geology, mineral physics, planetary science, and geodesy. We clarify and consolidate terminology across geodynamics and numerical modelling to set a standard for clear communication of modelling studies. All in all, this paper presents the basics of geodynamic modelling for first-time and experienced modellers, collaborators, and reviewers from diverse backgrounds to (re)gain a solid understanding of geodynamic modelling as a whole. [ABSTRACT FROM AUTHOR]

Magnesium is one of the largely available elements in the earth's crust. It has a low structural density with high specific strength. This unique material property has forced an increase in the use of magnesium and its alloys in various applications pertaining to industrial sector, automobiles, aerospace and biomedical. Since magnesium is a highly reactive metal, it is prone to higher rate of corrosion as compared to its counterparts. Thus, it is essential to analyze the corrosion behavior of magnesium and its alloys in its applications. An appropriate process is to be followed in the design and development of magnesium alloys which overcome the limitations of magnesium and enhance the desired material properties in accordance to their applications. This review paper summarizes the importance of magnesium and its material properties. The influence of various alloying elements on the mechanical properties of magnesium is reviewed. The broad classification of Mg alloys and their behavioral trends are detailed. The corrosion behavior of magnesium and the influence of corrosion products on the material characteristics of magnesium, in aqueous medium, are discussed. The manufacturing techniques of magnesium alloys along with the secondary techniques are also covered. The various applications and the limitations of magnesium in these applications are covered. A complete section is dedicated towards detailing the recent trends of magnesium (Mg) alloys, i.e., the biodegradable nature and applications of Mg alloys. The influence of biocorrosion on Mg alloys and techniques to overcome it have been deliberated. This paper provides a thorough review on recent developments of magnesium with respect to engineering applications. [ABSTRACT FROM AUTHOR]

The paper presents a new physicochemical model of the formation of nanosized diamonds from an OHC fluid system under low temperature and pressure conditions corresponding to the graphite stability area. This model in general explains the specific features of the composition of gas mixtures for CVD and hydrothermal synthesis in terms of diamond growth and formation under metastable conditions. It also explains the origin of nanodiamonds and microdiamonds in metamorphic rocks of the Earth's crust and the genesis of nanodiamonds in outer space at low temperatures and pressures. [ABSTRACT FROM AUTHOR]

The dynamic and melting processes of a ridge-centred plume have been investigated in a companion paper by Ruedaset al.(hereafter referred to as Paper I) in a set of 3-D numerical fluid dynamic models with varying plume excess temperatures and melt extraction thresholds. In Paper I, the modelled thickness of the generated crust has been compared to observations of the Icelandic crust. Using the results of those plume models magnetotelluric (MT) transfer functions and seismic velocity anomalies are predicted in this paper. Together with Paper I, a dynamically consistent set of geophysical observables of a ridge-centred plume is presented and applied to Iceland.Temperature, partial melting and the connectivity of the melt phase influence the electrical conductivity of crust and mantle rocks. The temperature and melt fraction of our plume models are used to calculate 3-D conductivity models for MT modelling. For the melt geometry ellipsoidal inclusions with appropriate aspect ratios were assumed to control melt connectivity. The resulting transfer functions are compared to each other and to models not including a plume to separate signals from the ridge and the plume. They may be applied to observed MT measurements. If the plume head contains only 1 per cent of melt, the plume signal cannot be distinguished from the ridge signal, at least 3 per cent melt is needed for such distinction. The other predicted observables calculated from the different numerical models are seismic velocity anomalies. The temperature-inducedVP andVS anomalies were estimated including anharmonic and anelastic effects as well as the water induced increase of dislocation mobility that lowers seismic velocities. Realistic melt geometries, as observed in laboratory experiments, were used to calculate the effect of partial melts on the seismic velocities.VS anomaly distributions are synthesized from the different plume models and compared to seismic observations. To reconcile seismic anomalies of the plume head and plume stem, a wet plume stem overlain by a partially molten, dehydrated plume head is favoured.The combined interpretation of available observations, crustal thicknesses (Paper I) and seismic results, with our dynamic plume models (Paper I) leads to a favoured plume model with 135 K excess temperature and a vertical velocity of approximately 13 cm yr−1 at 200 km depth, with 1 per cent melt extraction threshold, and a melting zone of approximately 500 km width and 100 km depth extent. [ABSTRACT FROM AUTHOR]

Most of the rock masses in the outer crust of the Earth are discontinuous. They are divided by joints, faults, fractures, etc. And those discontinuities, generally referred to as joints, greatly affect the property of the rock masses. The paper experimentally investigates the stress wave propagation crossing the jointed specimens. The tests were conducted on the split Hopkinson pressure bar (SHPB). The test specimens consist of two parts cast by cement mortar. Both parts have an irregular surface, and they were designed to match each other completely. The surfaces where two parts meet make an artificial joint. The surfaces of the joints were scanned by a three-dimensional scanner to obtain its actual topography and then to calculate the roughness of the surface, i.e., the joint roughness coefficient (JRC). A set of jointed specimens with JRC ranging from 0 to 20 were made and used in dynamic compression experiments. During the tests, signals were captured by strain gauges stuck on the incident and transmitted bars of the SHPB apparatus. The incident, reflected, and transmitted waves across the jointed specimens were obtained from the test records. We found out that more stress wave would transmit through the jointed specimen with larger JRC. Besides, collected data were processed to get the dynamic stress-strain relation of jointed specimens and the stress-closure curves of the joints. The results show that the joint increases the deformation of the specimen, and the stiffness of the jointed specimen would increase slightly when the joint is rougher. [ABSTRACT FROM AUTHOR]

Orogenic gold deposits provide a significant source of the world's gold and form along faults over a wide range of crustal depths spanning sub-greenschist to granulite grade faces, but the source depths of the gold remains poorly understood. In this paper we compiled thirty years of long-period magnetotelluric (MT) and geomagnetic depth sounding (GDS) data across western Victoria and south-eastern South Australia that have sensitivity to the electrical resistivity of the crust and mantle, which in turn depend on past thermal and fluid processes. This region contains one of the world's foremost and largest Phanerozoic (440 Ma) orogenic gold provinces that has produced 2% of historic worldwide gold production. Three-dimensional inversion of the long-period MT and GDS data shows a remarkable correlation between orogenic gold deposits with > 1 t production and a < 20 Ω m low-resistivity region at crustal depths > 20 km. This low-resistivity region is consistent with seismically-imaged tectonically thickened marine sediments in the Lachlan Orogen that contain organic carbon (C), sulphides such as pyrite (FeS2) and colloidal gold (Au). Additional heat sources at 440 Ma due to slab break-off after subduction have been suggested to rapidly increase the temperature of the marine sediments at mid to lower crustal depth, releasing HS− ligands for Au, and CO2. We argue that the low electrical resistivity signature of the lower crust we see today is from a combination of flake graphite produced in situ from the amphibolite grade metamorphism of organic-carbon in the marine sediments, and precipitated graphite through retrograde hydration reactions of CO2 released during the rapid heating of the sediments. Thus, these geophysical data image a fossil source and pathway zone for one of the world's richest orogenic gold provinces. [ABSTRACT FROM AUTHOR]

The dynamic evolutions of fluid-mineral systems driving large-scale geochemical transformations in the Earth's crust remain poorly understood. We observed experimentally that successive sodic and potassic alterations of feldspar can occur via a single self-evolved, originally Na-only, hydrothermal fluid. At 600 °C, 2 kbar, sanidine ((K,Na)AlSi3O8) reacted rapidly with a NaCl fluid to form albite (NaAlSi3O8); over time, some of this albite was replaced by K-feldspar (KAlSi3O8), in contrast to predictions from equilibrium reaction modelling. Fluorine accelerated the process, resulting in near-complete back-replacement of albite within 1 day. These findings reveal that potassic alteration can be triggered by Na-rich fluids, indicating that pervasive sequential sodic and potassic alterations associated with mineralization in some of the world's largest ore deposits may not necessarily reflect externally-driven changes in fluid alkali contents. Here, we show that these reactions are promoted at the micro-scale by a self-evolving, kinetically-driven process; such positive feedbacks between equilibrium and kinetic factors may be essential in driving pervasive mineral transformations. This paper reveals that potassic alteration can be triggered by Na-rich fluids, indicating that pervasive sequential sodic and potassic alterations associated with mineralization in some of the world's largest ore deposits may not necessarily reflect externally-driven changes in fluid alkali contents. [ABSTRACT FROM AUTHOR]

Pan et al. presented a new analytical approach to compute the elastic load Love numbers (ELLNs) for an elastic, transversely isotropic, spherical, layered and self-gravitating Earth with a layered fluid core. Any layer or shell can be compressible or incompressible. Here, we enhance this formulation by replacing the direct propagator matrix with the stiffness matrix, which allows us to calculate the ELLNs out to any high degree n. This allows users of the ELLNs to compute point- and disc-load Green's functions without relying on untested assumptions about the onset of asymptotic behaviour. The new method also allows us to compute the ELLNs for Earth models containing fine layers, and enables ELLN users to correctly compute the near-field response to very small disc loads. We demonstrate, using a modified preliminary reference Earth model (PREM) Earth model incorporating refined crustal structure, that the degree n associated with the onset of asymptotic convergence of the ELLNs is very strongly influenced by the fine details of shallow elastic structure, and that this onset degree can exceed 100 000 for plausible Earth models in which the outermost layer has a thickness of 1 km or less. We further demonstrate the excellent numerical stability attainable using the stiffness matrix rather than the direct propagator matrix. We implement our algorithms in a MATLAB library called ELLN, and provide the software in two versions (with and without a graphical user interface), the user guides, and example input files in the Supporting Information. [ABSTRACT FROM AUTHOR]

Soft rock masses represent a significant percentage of rock material on the earth's crust. The engineering properties of these rocks are related to their composition, geological history, and degree of weathering. Mudrocks (claystone, mudstone, argillite), marl, shale, sandstone, and conglomerates with weak cementing material are the most common example of these rocks which can be subjected to a wide variation of their engineering properties. Generally, they can be grouped in a broad sense, as geological materials with very low intact rock properties, namely, high deformability and low strength that span the range between soils and hard rocks. This paper is organized to suggest a classification for these rocks, dealing with the main geological and engineering aspects and features that characterize these materials. The two indices of soft rock number (SRN) and soft rock activity (SRA) have been introduced in this classification. The SRN is obtained based on the geomechanical properties of soft rocks, and it is within a range from 0 to 100 (0 for very weak rocks and 100 for strong ones). On the other hand, the SRA index, which indicates how rocks respond to disturbance, is calculated using an empirical graph. This index can have values from 0 to 1. If the index is closer to 0, the rock mass will be less sensitive to disturbance. Based on the two indices, the weakest group of soft rocks, which is called swelling soft rocks, has SRNs less than 20 and SRAs higher than 0.8. Excavation of these rocks can be accompanied by various types of failures. Moreover, in high-strength soft rocks, SRNs and SRAs have values higher than 80 and lower than 0.25, respectively. These rocks have good geomechanical properties and the lowest sensitivity to disturbance, so excavation them results in the fewest failures. [ABSTRACT FROM AUTHOR]

Tourmaline is a common mineral in granites and metamorphic rocks in collisional orogens. This paper describes graphite-bearing, metasomatic tourmalinites in sillimanite-zone schists of the Proterozoic Black Hills Orogen, South Dakota. The tourmalinites bound quartz veins and beyond about 1 m grade into schists with disseminated tourmaline, and ultimately tourmaline becomes only a trace, intrinsic phase in the schists. Next to the quartz veins, tourmaline has almost completely replaced schist minerals, including biotite, muscovite, and plagioclase. The tourmaline is generally anhedral and follows the original foliation direction of the schist. However, tourmaline is euhedral in quartz veinlets cutting through the tourmalinites. Tourmaline is compositionally zoned from having about 22 to 2% of apparent Al occupancy on the Y sites. There are very good negative correlations of Y(Fe2++Mg2+), XCa2+, and YTi4+ with YAl3+, and a very good positive correlation of X-site vacancies with YAl3+. Mg# [molar Mg2+/(Mg2++Fe2+)] is fairly invariant at approximately 0.5, which is somewhat higher than that in the precursor biotite. This is in contrast to tourmaline in the neighboring peraluminous Harney Peak leucogranite where the range of Y site occupancy of Al is small at about 20%, but the Mg# ranges from 0.12 to 0.5. The compositional trends in the metasomatic tourmaline are dominated by the exchange Xo + 4 YAl3+ = XCa2+ + 3 Y(Fe2++Mg2+) + YTi4+. Mass-balance calculations suggest the metasomatizing fluid brought in H+ and B(OH)3 and removed K+, SiO2, and some Fe2+ during tourmalinization. Other elements in the tourmaline largely reflect the bulk composition of the replaced schist. The calculations show that silica in the quartz veins was locally derived, not brought in by the metasomatizing fluid. Interstitial graphite in the tourmalinites shows precipitation of carbon from the methane-bearing fluid. The study demonstrates an important effect of boron transfer by fluids during metamorphism and magmatism in the Earth's crust. [ABSTRACT FROM AUTHOR]

The paper contains an analysis of S-velocity distribution in the crust and upper mantle beneath the Bohemian Massif, which is the second biggest Variscan outcrop in Europe. It occupies mainly the west part of Czech Republic and also part of south-west Poland and south-east Germany. We use data from 10 permanent stations set in the region. Some previous papers relate to the same scope but use linear methods to inverse receiver function. Our new approach involves Monte Carlo techniques for inversion procedure, which is more convenient and robust for such a non-linear task. The result of Monte Carlo inversion is compared with the previously achieved one. The obtained Moho depths vary from 29 km in the north-west part of the Bohemian Massif to 38 km in the south and south-east and are consistent with other papers. Some discrepancies occur in the middle and upper crust. [ABSTRACT FROM AUTHOR]

Seismic anisotropy is evidenced in the inner core, upper mantle and the lower crust in large scale, and the evidence is generally provided by shear wave splitting analysis. Here this paper searches for the evidence of anisotropy in the uppermost crust, by using P-wave arrival times from crosshole seismic measurement to directly estimate velocity anisotropy associated with the fine-layering effect of multiple sedimentary beds. Conceptually fine layering causes the so-called VTI (vertical transverse isotropy) anisotropy with a vertical symmetry and the effect is parametrized by the horizontal and vertical velocity ratio. It is found however that the VTI anisotropic parameter does not have a simple vertical symmetry but is also azimuth dependent. This azimuthal anisotropy may reflect the fracture orientation due to large-scale tectonic movements, and is very important in the production of oil reservoirs, as the seismically fast directions can indicate preferred directions of fluid flow. This paper presents innovative methods for anisotropy analysis in both vertical and horizontal plane. Integrated seismic anisotropy interpretation clearly indicates distinguished strain orientations forming fractures in Oligocenic, Miocenic and Pliocenic sediment, in the edge of the extensional basin immediately next to Tan-Lu Fault, an active continental strike-slip fault zone. [ABSTRACT FROM AUTHOR]

The paper presents the results of GNSS observations, provided by the authors in 2010-2019 years, in the zone of contact of tectonic structures of the Siberian platform, West-Siberian plate and West-Sayan orogenic area. We presented the first time assessment of the velocities of modern horizontal movements and the structural-kinematic model of block movements in a southern sector of the Yenisei Ridge. This model enables to assess the geodynamic safety of disposal of high-level radioactive waste in granite gneisses rocks of the Nizhne-Kansk massif. [ABSTRACT FROM AUTHOR]

210Pb is an environmental radionuclide with a half-life of 22.3 years, formed in the atmosphere via radioactive decay of radon (222Rn). 222Rn itself is a noble gas with a half-life of 3.8 days and is formed via radioactive decay of uranium (238U) contained in the Earth crust from where it constantly emanates into the atmosphere. 210Pb atoms attach to aerosol particles, which are then deposited on glaciers via scavenging with fresh snow. Due to its half-life, ice cores can be dated with this radionuclide over roughly one century, depending on the initial 210Pb activity concentration. Optimum 210Pb dating is achieved for cold glaciers with no – or little – influence by percolating meltwater. This paper presents an overview which not only includes dating of cold glaciers but also some special cases of 210Pb applications in glaciology addressing temperate glaciers, glaciers with negative mass balance, sublimation processes on glaciers in arid regions, determination of annual net snow accumulation as well as glacier flow rates. [ABSTRACT FROM AUTHOR]

Oroclines are map‐view deformation of Earth's crust resulting from bending of quasi‐linear elements. The Central Asian Orogenic Belt (CAOB) is one of the largest and long‐lived accretionary orogens in the world and mainly consists of the Kazakhstan and Tuva–Mongolian oroclines. However, the mechanism of the oroclines is still in debate. Therefore, in this paper, we combine some investigation of high bathymetric relief resistance to subduction, review oroclinal bending models of the Kazakhstan Orocline, and propose a tentative model that involves asymmetric rollback in response to seamounts subduction and accretion, followed by bending associated with the convergence of the Siberian and Tarim cratons. Moreover, the role of pinning due to seamount and ridge subduction is probably more important than the convergence of continents in the CAOB. This model is compatible with the occurrence of seamounts, the spatial migration of intra‐oceanic arcs, and the development of multiple rollback processes during amalgamation of Eurasia. However, only geochemical and geochronological data will enable definition of the seamounts in CAOB so far, without much matching structural data. So we need more work to understand seamounts subduction and accretion as well as orocline bending in CAOB. [ABSTRACT FROM AUTHOR]

In research into various hydrophysical and hydroacoustic wave processes, it is extremely important to know the regularities of their propagation in the sea at decreasing depths, especially in the shelf areas, and also to know the regularities of their transformation into seismoacoustic processes in the earth crust. In the course of the processing and analysis of the experimental data of our complex experiment, in this paper we investigate these regularities. In our experiment, we used a low-frequency hydroacoustic transmitter that generated harmonic oscillations at the frequency of 22 Hz and received hydroacoustic systems with a shore laser strainmeter. It was established that hydroacoustic waves, propagating at the shelf of decreasing depth, transform into seismoacoustic waves at the depth of the sea equal to or less than a half-length of the hydroacoustic wave. A comparison of the results of this work with earlier-obtained results allows us to state that such regularities should be inherent to all hydrophysical and hydroacoustic processes. [ABSTRACT FROM AUTHOR]

Post-seismic deformation caused by the 2004 Sumatra-Andaman Earthquake has been observed by space geodetic techniques such as the Global Positioning System (GPS) and the Gravity Recovery and Climate Experiment (GRACE). To estimate such deformation with a spatial scale exceeding 100 km, we can use theories of global post-seismic deformation in which the Earth is treated as a self-gravitating viscoelastic sphere. Previous theories have imposed limitations on employed earth models, such as neglecting compressibility and time variation of self-gravitation or simplifying the radial profile of the viscosity. This is because the normal mode method on which these theories are based cannot evaluate a denumerably infinite set of eigenmodes that will appear when those limitations are removed in the practical computation. To bypass this difficulty, in our previous paper, we showed that the numerical inverse Laplace integration with a rectangular path enabled us to obtain the vertical deformation without using those approximations. In this paper, we apply the same method to the horizontal deformation for a complete set of the fault mechanisms (strike-slip, dip-slip and vertical and horizontal tensile). Next, we reveal error sources in our approach. The largest error arises in different selections of the integration path. This error is less than 1 per cent in the lower-degree deformations ( n∼ 10) and 0.1–0.5 per cent in the higher-degree ones , relative to the result obtained with an independent method. Finally, we elucidate differences in far-field deformations obtained for the earth model employed in this study and those used in the previous studies for a large dip-slip event . The result shows that (1) differences of 6–50 per cent are seen in the coseismic offset and (2) horizontal rate differences of 1–5 mm yr−1 (5–25 per cent of the rates) are observed at the epicentral distance of 100 km during the first thirty years after the event. These differences are detectable with GPS. Therefore, for theory to meet observational accuracy, effects of compressibility and stratification on global post-seismic deformation should be considered. [ABSTRACT FROM AUTHOR]

Seismic wavefields reflected from the Earth's crystalline crust often appear quite complex due to the non-horizontally layered, seemingly random spatial patterns of velocity structure. Deterministic mapping of such a velocity field is often impractical, therefore, we rely on stochastic descriptions to quantify textural aspects of a given Earth model. This paper introduces an iterative method to invert (in 1-D) a reflected seismic wavefield for vertical stochastic parameters. In a previous method, standard deconvolution is used to form an estimate of the Earth's reflectivity. Numerical integration of the resulting reflectivity is an estimate of the binary velocity perturbation model to which we can fit a theoretical von Kármán stochastic autocorrelation function. In this paper, an improved iterative model-based approach is introduced. The algorithm estimates the vertical von Kármán stochastic parameters by iteratively modifying a deconvolution filter based on previously estimated von Kármán model parameters. By inverting synthetic seismic data, its shown that this iterative approach is more stable numerically than an earlier algorithm, and is able to recover both the vertical characteristic length and the Hurst exponent. The method is sensitive to noise in the data because the noise has a stochastic behaviour similar to that of the data. This new method is applied to a single common shot record that was recorded as part of the PASSCAL Basin and Range experiment and recovers values of stochastic parameters that are consistent with observations of exposed crustal sections. [ABSTRACT FROM AUTHOR]