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.
