An approximate but accurate calculation of seismic wavefields in smooth (without interfaces) isotropic or anisotropic, inhomogeneous, attenuating media using ray theory is possible with the aid of the so-called weak-attenuation concept (WAC). In WAC, the attenuating medium is regarded as a perturbation of an elastic reference medium. The extension of this concept to layered media was prevented for a long time by problems with evaluation of the reflection and transmission (R/T) coefficients of plane waves in attenuating media, and by the role of inhomogeneous waves in this process. The R/T coefficients represent a fundamental part of ray calculations in layered media. It turned out that the problems are related to a limited applicability of the correspondence principle to reflection and transmission. Recently, this problem was solved by the use of WAC. It opened the way to the calculation of seismic wave fields in layered, attenuating media. Before such a calculation, it is necessary to solve several important problems. It is well known that the incidence of a wave at an interface separating attenuative media generates inhomogeneous body waves. These waves are not implicitly included in WAC. Therefore, it is important to find out how their absence affects the results of ray calculations with WAC. In this paper, we check the accuracy of such calculations by comparing synthetic ray seismograms with full-wave seismograms, which are considered to be an accurate reference. For simplicity and transparency, we focus on the problem of reflection and transmission of SH-waves in 2D horizontally layered isotropic attenuating media, since SH-waves are decoupled from P–SV waves and thus allow a simpler treatment. Another reason for the use of SH-waves is the availability of the full-wave code designed for SH-waves. Use of more complicated structures and other types of waves would lead to artefacts, which would mask the effects of attenuation. The results of the comparison show that outside singular regions, such as the critical region or the vicinity of the Brewster angle, ray theory with WAC provides results that closely approximate those obtained using full-wave modeling. Applicability of WAC to other types of waves and more realistic structures is thus open.
The deflection of the vertical (DOV), defined by the angle between the plumb line and the normal to the reference ellipsoid, plays a crucial role in geodesy and geophysics, particularly in geodetic data processing, geoid determination, and gravity field studies. Compared with traditional astro-geodetic methods, the determination of the DOV from gravity observations is more efficient and practically feasible. Moreover, gravity gradients contain richer high-frequency (short-wavelength) information than gravity anomalies. Therefore, they provide a promising data source for high-resolution DOV determination. In this context, this study employs three methods to compute the DOV from the vertical component of gravity gradients: the spherical numerical integration formulation, the planar numerical integration formulation, and the planar closed-form solution. Starting from the spherical formulation, a planar approximation is derived, and a corresponding closed-form solution under this approximation is further developed. Two test regions are selected: one bounded by [0°E, 2°E] in longitude and [0°S, 2°S] in latitude, and another in [150°W, 152°W] [0°, 2°N]. Closed‑loop tests based on the EGM2008 model confirm the theoretical consistency of the three methods. In a separate validation, the results were compared with DOV data from the Scripps Institution of Oceanography (SIO) model. The strong agreement between the computed DOV and the SIO model confirms the accuracy of the algorithms proposed in this study. A comparison of computational times with implementations based on the spherical formulation further demonstrates the high efficiency of the planar approximation. In addition, Graphics Processing Unit (GPU) parallel computing was applied to accelerate the computations. This efficient approach provides a valuable alternative for high-resolution DOV determination.
The Eger Large-N International Seismic Experiment (ELISE) is a major cross-border project deploying a temporary network of over 300 broadband and short-period seismic stations in the West Bohemia/Vogtland region, located at the border of Czechia and Germany. This experiment offers new research opportunities in one of the most seismically and geodynamically active intraplate regions in Europe, characterized by recurrent earthquake swarms resulting from magmatic crustal fluids and mantle CO₂ degassing processes. The collision and thrusting of Variscan tectonic domains have created a unique natural laboratory to investigate how ancient structures influence present-day magmatic processes and fluid–rock interactions. ELISE aims to address fundamental questions regarding the origin of swarms, their dynamics, and hazard potential, as well as their relationship with geodynamic activities in the region. The stations of this dense array have been operating since August 2025 and will record for up to 18 months. They will enable high-resolution imaging of crustal structures through the use of high-resolution earthquake locations, ambient noise tomography, receiver function analyses, and local earthquake tomography. Based on previous experience, we hypothesize that intensifying seismic networks will reveal at least ten times more local earthquakes, ultimately clarifying the mechanisms of swarm earthquakes by constraining fluid migration paths and structural and geological boundary conditions. Better earthquake locations, together with high-resolution subsurface models of different quantities, will provide new insights into the interaction between tectonic and fluid-induced seismicity revealing the possible role of carbonate brines and melts in the formation of swarms. This will improve our understanding of geodynamic and fluid-magma interactions in intraplate tectonic settings. This paper provides an overview of the ongoing ELISE experiment. It outlines its goals, scientific framework, and expected contributions.
The prediction products of the polar motion parameters play a crucial role in precision orbit determination, high-precision positioning, timing services and other fields. In this paper, we proposed employing the Nonlinear Auto Regressive (NAR) neural network model for polar motion prediction. The network parameters are determined through the cross-validation method, leading to the establishment of the NAR neural network prediction model. The EOP 20 C04 product provided by the International Earth Rotation and Reference Systems Service (IERS) was utilized as experimental data, and 365 sets of ultra-fast forecasts spanning 1—7 days were conducted for the polar motion parameters. Furthermore, we also discussed the optimal amount of data for NAR, it was found that the training accuracy is optimal when using a 10-year dataset. Compared with the LS + AR model, the proposed method achieves an average improvement of 5.82
The processes governing magma ascent from subvolcanic reservoirs to emplacement at shallow crustal levels continue to pose a central challenge in volcanological research. To contribute to this long-standing scientific debate, we examine the vent-dike-lava flow system of the Ortiz Mountain volcanic complex, which intrudes Pliocene Rio Grande rift sediments, basaltic volcanic rocks, and older Oligocene sediments. Our study investigates the magmatic plumbing architecture, focusing on the relationships between an exposed intrusion and the surface volcanic features. Twenty sampling sites were collected for anisotropy of magnetic susceptibility (AMS), paleomagnetic, rock magnetic, and structural studies to characterize the magma emplacement, remanence behavior, and the overall vent-dike-lava flow system. Paleomagnetic data from half the sampling sites yield high-quality demagnetization data that are well grouped at the site level. The site mean directions of these locations are discordant to the Pliocene reversed polarity expected field direction. Thin section and rock magnetic experiments constrain the magnetic mineralogy to a cubic Fe-Ti oxide, likely titanomagnetite, some maghemite, minor Fe-sulfides, and traces of titanomaghemite. The magnetic domain size ranges from pseudosingle to multidomain grains. AMS ellipsoids are predominantly oblate, indicating magma flow directions that are either steeply inclined or sub-horizontal and directed away from the central vent. Combined field observations and laboratory data suggest initial magma ascent through a centralized vertical conduit, contributing to cone construction. A disruption in the plumbing system led to southwestward dike propagation ( 800 m), which ultimately breached the surface and erupted as a lava flow. The resulting volcanic construct illustrates a vent-dike-lava flow system, where subsurface magmatic processes are spatially and temporally linked to surface volcanic features. The results underscore the importance of integrated field and laboratory approaches to reveal the hidden plumbing architecture of small volcanic systems as well as the dynamic pathways magma follows from depth to eruption.
The gravity aspects (Marussi tensor, gravity invariants, their special ratio, strike angles, and virtual deformations) have been tested and proven as efficient to describe various geological features and stresses in the Earth (impact craters, volcanoes, ground water or hydrocarbon deposits). Here, we utilise the gravity strike angles to check known localities and extend existing terrestrial estimates (coming mainly from the USGS) of hydrocarbon occurrences in Ukraine, Crimea, and the Black Sea. The agreement between terrestrial and satellite data is good. Our method is completely independent of any traditional approach. It is a remote sensing method providing a preliminary, cheap indicative approach to identify density/porosity anomalies that may be responsible for further hydrocarbon occurrences in those areas.
Serpentinization significantly alters orogenic peridotites, but the processes controlling the magnetic fabric development remain incompletely understood, particularly the roles of mineralogy, fluid availability, and deformation. This study addresses this gap by combining petrography, rock magnetic measurements, and numerical modeling on samples representing moderate to complete serpentinization. Magnetic properties indicate a mix of paramagnetic serpentine and ferrimagnetic magnetite, with anisotropy of magnetic susceptibility fabrics showing spatial patterns linked to serpentinization degree and structural setting. Microstructural observations reveal that serpentine and magnetite grow parallel or at characteristic angles to primary fabrics, while deviations reflect post-serpentinization deformation. Numerical modeling confirms that magnetic fabric orientation depends on the interaction of primary mineral crystallographic preferred orientation and topotactic serpentinite growth. These results demonstrate the complex interplay of mineralogy, fluid-rock interaction, and deformation in controlling magnetic fabric evolution during serpentinization in orogenic peridotites.
Proximal sensing receives increasing attention in soil science and potting media research because of favorable simplicity, speed and nature-friendly approaches. The aim of the present study is to test the utility of the environmental magnetic methods for quality characterization of various potting substrates. A pilot collection of ten samples from commercially available growing media (potting soils, potting mixes and vermicomposts) was analyzed using mineral magnetic methods (magnetic susceptibility (ꭓ), percent frequency-dependent magnetic susceptibility (ꭓfd
Hematite, a common iron oxide carrier of remanence magnetization, is the most oxidized mineral in the Fe-Ti–O system. Despite its significance, aspects of its magnetic structure remain largely unexplored. While general properties have been described in the early twentieth century, a comprehensive model of the magnetic properties of hematite remains elusive. This research endeavours to provide deeper insights into the internal structure of the anisotropy within the basal plane. Torque curves exhibiting a distinct 6θ term yield a new value for the anisotropy constant within the plane of K3= 25 Jm-3, the highest reported value by this method. Additionally, the irreversible torque curve reveals that magnetization, and its rotation, plays a role. Rotational hysteresis facilitates our comprehension of the anisotropy field and energy storage within the anisotropy plane.
The anisotropy of magnetic susceptibility (AMS) arises from the preferential alignment of minerals within a rock or sediment, which is known as a magnetic fabric. To interpret magnetic fabrics in a geological context, it is essential to understand how the constituent minerals in a rock contribute to the measured fabric. We present a new analysis, employing a micromagnetic approach, to characterize the susceptibility of non-interacting particles of magnetite in the single-domain (SD) or single vortex (SV) domain state. The orientation and magnitudes of the principal susceptibilities can be derived from a susceptibility map. We investigate the combined role of magnetocrystalline and shape anisotropy in rotationally oblate and prolate and triaxial ellipsoidal particles of varying axial ratio, on the orientation and magnitude of the AMS. SD particles exhibit an inverse magnetic fabric, where the smallest susceptibility is along the easy axis of magnetization of the ellipsoid. SV particles, on the other hand, can have either a normal magnetic fabric when the particle elongation is not large, i.e., the largest susceptibility is along easy axis, or an inverse fabric when the particle is more strongly elongated. The underlying explanation for the variation of fabric lies with the relative orientation of the remanence carrying vortex core within a particle with respect to the principal axes of the ellipsoid. Susceptibility maps can also be generated for assemblies of particles with variable orientation, which allows us to examine how orientation influences the total AMS. Although we present a limited number of simple models, the method can be extended to more natural mineral shapes and an array of particles that represent their distribution within a rock or sediment.
The behaviour of the quiet daily variations during different levels of solar activity over midlatitudes in Europe was the motivation for this study. The main aim was to determine the quiet daily variations from the Lonjsko Polje observatory (Croatia), for the first time. The hourly mean values of the three orthogonal components from 2013 to 2023 were used to examine and build an empirical model of the quiet daily variations for Lloyd’s seasons. An empirical model with 1071 coefficients per component was developed based on the assumptions that it depends on local time, lunar age, season, and solar activity, represented by solar radio flux at 10.7 cm. The obtained model suggests that amplitude levels rise, and phase variations are affected by increasing solar activity. The derived seasonal variations were compared to the variations from the Fürstenfeldbruck, Panagjurishte and Tihany observatories during 2013−2021. Due to the absence of data from Lonjsko Polje during periods of higher solar activity, seasonal variations were examined using records from Fürstenfeldbruck and Panagjurishte over the period 1956−2021 and Tihany over 1997−2021. The modelled patterns of seasonal variations with different levels of solar activity showed good agreement with the observations. The seasonal variations from Fürstenfeldbruck and Panagjurishte averaged over each of six consecutive nonoverlapping 11-year intervals during 1956−2021 are highly correlated, while some scatter up to 7 nT is observed for each geomagnetic component, depending on local time. The seasonal variations at Lonjsko Polje for the period of 1956 to 2012 were reconstructed using a multilinear regression analysis of data from Fürstenfeldbruck and Panagjurishte, with the maximum amplitudes of 30, 90, and 40 nT for the north, east, and vertical components, respectively. The results from this study could lead to a possible investigation of the equivalent ionospheric and induced currents responsible for derived variations.
The paleogeographic evolution of the Antarctic Peninsula during the Gondwana breakup remains poorly constrained. Reconstructing the eruptive sources of the voluminous Jurassic Chon Aike Province is crucial for refining or challenging existing tectonic models. This study presents new Anisotropy of Magnetic Susceptibility (AMS) data from Mid-to-Late Jurassic pyroclastic units in the northern Antarctic Peninsula to address these uncertainties. Bulk magnetic susceptibility values between 30–80 µSI, thermomagnetic curves, and hysteresis cycles indicate a normal (non-inverse) AMS fabric. Lack of evidence of tectonic overprint sustains a primary origin for the AMS fabric. Volcanic paleoflow directions were determined using K3 imbrication and, to a lesser extent, K1 magnetic lineations. Our results for the pirolastic Kenney Glacier Formation reveal a significant shift in volcanic sourcing: a source area located to the NW of Mount Flora in the basal units (Kenney 1 and lower Kenney 2 Members). A systematic change in the source area, coming from the ESE in Kenney 2 and 3 and from the SE in Kenney 4 Member. Integrating these results into a 160 Ma paleoreconstruction, we propose a model for the Kenney Glacier Formation that aligns with current tectonic frameworks for the Graham Land Volcanic Group. In this restored geometry, flows originated from the SE (Kenney 1), shifting to the NNW (Kenney 2 and 3), and finally to the NE (Kenney 4). These findings provide evidence of shifting volcanic centers during the V2 episode of Jurassic magmatism in West Gondwana.
Magnetic fabrics are commonly studied to understand the magma flow in volcanic and hypovolcanic settings. In this work we present a magnetic fabric study in the Sierra de Javalambre (SE Iberian Chain), a geological unit that includes a swarm of Mesozoic volcanic intrusive and extrusive bodies associated with a hotspot and extensional deformation in Eastern Iberia during the Mesozoic. The sill sampled in this work is constituted by alkaline dolerites (ocean island basalts, OIB composition) and is a part of more than a hundred outcrops emplaced in Upper Triassic (Keuper facies) diapiric units and Jurassic limestones. The presence of Ti-poor titanomagnetite in the studied hypovolcanic rocks is inferred from temperature-dependent magnetic susceptibility curves and also from analyses of the three components isothermal remanent magnetization (IRM), since the decay of the magnetic susceptibility and the soft axis (0.12 mT) of the IRM occurs at 580°C. The magnetic susceptibility shows high values, in average 17554 × 10–6. The anisotropy of the magnetic susceptibility shows some dispersion of the maximum and intermediate axes on the bedding plane, whereas the minimum axes are clustered almost perpendicular to the bedding plane for the 158 standard analyzed samples. The magnetic lineation (clustering of the maximum axes of the anisotropy of magnetic susceptibility) is bimodal with WNW-ESE and NNE-SSW directions in the in-phase magnetic susceptibility, and can be interpreted as the flow direction of the magma controlled by the NW–SE and N-S extensional fault systems during the basinal (Jurassic) stage.
The anisotropy of the magnetic susceptibility (AMS) in mudrocks has been widely used to study orogenic belts due to their sensitivity to strain, while paleomagnetism remains the most effective method to quantify vertical axis rotations (VARs) resulting from the accommodation of along-strike variations in shortening. However, AMS can be also eventually used as a passive marker to detect VARs and the integration of both techniques offers a powerful approach to understand the tectonic evolution of fold-and-thrusts-belts. In this work, a combined AMS and paleomagnetic study along a stratigraphic section of continental rocks from the Campodarbe Formation in the Jaca-Pamplona Basin, southern Pyrenees, was carried out. This stratigraphic section (Martes section) records the tectonic evolution of this part of the basin from Priabonian to Rupelian times. The magnetic fabrics show the imprint of early stages of deformation, characterized by dominantly oblate ellipsoids and WNW-ESE horizontal magnetic lineations (axes of maximum magnetic susceptibility kmax), parallel to bedding and the main regional structures. In the lower part of the section, kmax axes trend around 290º, gradually rotating to 270º towards the top. The AMS is interpreted as locked under the imprint of the layer parallel shortening (LPS) associated to the activity of the basement thrusts in the northern Jaca-Pamplona Basin. On the other hand, paleomagnetic data indicate clockwise VARs of 6º to 12º in the lower part of the section, and a counterclockwise rotation of 7º to 14º in the upper part. These differential rotations could result from lateral changes in the Biniés basement thrust or the Jaca thrust system that were active during Oligocene times. Both techniques record a net rotation of ca. 25º between the lower and upper part of the section, which support the interpretation that early-locked AMS behaves as a passive marker and validates its use for detecting and quantifying VARs.
The utilisation of magnetic fabric constitutes a rapid and non-destructive technique; however, its primary disadvantage is that it is carried by multiple magnetic phases. Consequently, it is imperative to furnish structural geologists with target rocks whose mineralogy is as elementary as possible in order to quantify strain. It is evident that non-metamorphic shales are of interest due to the fact that magnetic susceptibility is primarily exhibited by phyllosilicates, including smectites, illites and chlorites. The use of magnetic fabric facilitates the identification of the contribution of billions of these clay particles. The present study utilises published data to demonstrate the feasibility of employing scalar data for the purpose of monitoring the evolution of vertical compaction during diagenesis, or horizontal compaction during the development of layer-parallel shortening, or strain induced by fault propagation. The examples presented demonstrate that the quantification of strain is possible when cleavage is significantly oblique to the bedding. The extraction of these scalar data is facilitated by the measurement of a minimal quantity of unoriented shale fragments, thereby enabling the execution of large-scale statistical studies.
The model of transpression is a standard framework for tectonic studies. It describes homogeneous deformation in a weak zone between two obliquely convergent rigid blocks. Depending on the angle of convergence, pure shear-dominated transpression and wrench-dominated transpression (WDT) can be distinguished in which the lineation (first eigenvector of finite strain ellipsoid) is vertical or switches from initially horizontal to vertical. In practice, lineation is often determined using the AMS method, i.e. based on the preferred orientation of magnetic grains. Under special circumstances, such as transpression, this can lead to differences in lineation defined by the strain ellipsoid and lineation defined by grains. This paper aims to fill the gap in knowledge on this issue. Mathematical modelling based on continuum mechanics quantifies how the switching of lineation in WDT depends on the grain axial ratio. This process is projected into the tensor of magnetic anisotropy and may be further modulated by the presence of subpopulations of magnetic grains or the variability of their shape and magnetic properties. It is shown that the switching of AMS lineation in WDT occurs at lower strain than by the lineation defined by strain ellipsoid.
The formulae for the prevailing-frequency approximation of the coupling ray theory derived in the companion paper, are tested on several models displaying varying strength of anisotropy and containing various types of shear-wave singularities. Standard coupling ray theory applied to these models yields results of a high accuracy as follows from tests made in the past. Therefore, the results of the standard coupling ray theory are used as a benchmark in this study. The results of the tests show that the prevailing-frequency approximation of the coupling ray theory can serve as a perfect substitute of its standard counterpart. Use of the prevailing-frequency approximation simplifies and speeds up considerably the computational procedure and makes it comparable with the procedure for the calculation of separate waves in the ray-theory approximation.
The anisotropy of anhysteretic remanent magnetization (AARM) provides a powerful, nondestructive means of assessing magnetic fabrics. It is widely applied to infer strain and emplacement conditions in sedimentary, volcanic, and intrusive rocks. AARM is generally represented by a symmetric second-rank tensor describing its orientation, strength, and shape. AARM, however, departs from a tensorial shape when the number of grains carrying each directionally imparted anhysteretic remanence (ARM) varies with ARM orientation – a condition that arises when the alternating field (AF) over which the ARM is imparted does not fully activate the sample. Experimental data from a highly anisotropic ignimbrite sample, together with multiparticle modeling, show that such partial activation produces non-tensorial AARMs. Although this behavior complicates tensor analysis, non-tensorial AARM can reveal superimposed fabrics, provided that users can apply AF and ARM in a broad range of orientations. This article presents theoretical models that demonstrate non-tensorial behavior and explains how to utilize these properties to discern superimposed fabrics in natural samples.
Paleomagnetism relies4 on stable remanent magnetizations held in rocks to reconstruct the ancient geomagnetic field direction and intensity. However, rocks may carry secondary overprints that obscure or completely destroy the original signal. To study the stability of the magnetic vector(s), laboratories routinely apply static alternating field demagnetization along three orthogonal axes (AFD₃), which is fast, non-destructive, and easy to automate. Here, we present a multiparticle model that shows AFD₃ can deviate the natural remanent magnetization (NRM). Deviations can be avoided when fulfilling two conditions: (i) the NRM was acquired in a weak field where magnetization intensity varies linearly with field strength, and (ii) the sample is magnetically isotropic. The first condition is generally satisfied for rocks holding thermal or detrital remanent magnetizations, but not those affected by an isothermal remanence (e.g., lightning), even though AFD₃ is often used to remove them. In rocks with an anisotropic particle orientation distribution, stepwise AFD₃ progressively removes different coercivity subpopulations as a function of grain orientation so the effective remanence anisotropy of the surviving carriers changes during demagnetization. The anisotropy-driven deflection therefore evolves with AF step, producing curvilinear demagnetization trajectories. Our theoretical results argue for caution when applying AFD₃ to anisotropic samples or those with isothermal overprints. Undesired NRM rotation can be avoided by tumble demagnetization or mitigated by increasing the number of alternating field axis orientations.
