Pure and Applied Geophysics

Yurovskaya, Maria V.; Shokurov, Mikhail V.; Barabanov, Vladislav S.; Yurovsky, Yury Yu.; Kudryavtsev, Vladimir N.; Kamenev, Oleg T.

doi: 10.1007/s00024-024-03592-zpmid: N/A

The Black Sea coasts from the northwest of Turkey through Crimea to Georgia were strongly affected by severe storms in Autumn, 2023. The aim of the work is to compare the performance of different wave model approaches and wind datasets in extreme weather conditions in the Black Sea. The study covers the continuous period from the 1st to the 30th of November including two strong storms with wave heights up to 9–10 m. Wave simulations are performed using WAM and the 2D parametric model for surface wave development suggested in Kudryavtsev et al. (2021a). The wave models are forced by hourly wind fields from four datasets: ECMWF Reanalysis (ERA5), ECMWF Level-4 bias-corrected operational model, NCEP (CFSv2), and the regional WRF-ARW model with 6-hour NCEP/NCAR atmospheric forecast as input. The high-resolution Level-4 wave analysis for the Black Sea produced by CMEMS (also using WAM Cycle 6) is also considered. Simulation results are validated against along-track altimeter measurements of significant wave height, CFOSAT SWIM information on dominant wavelength and wave direction, and in-situ data from an oceanographic platform near Crimea. All models demonstrate their overall good performance, though third-generation wave spectral models give an expectedly higher correlation between simulations and observed data, while the parametric model is less accurate. Some recommendations to combine wind and wave models for the most accurate predictions are further given. As known, the wind speed fields produced by ECMWF are underestimated at winds higher than 15–20 m/s. While the wind correction is crucial when using the parametric model, WAM better reproduces the observed extreme waves without it. As also obtained, WAM simulations forced by NCEP and WRF winds lead to an overestimation of the largest storm waves. Increased resolution of the wind fields does not lead to significant improvement in the quality of wave predictions, which can be explained by the wind accumulation effect during wave development.

Nesteckytė, Laura; Stankūnavičius, Gintautas; Kelpšaitė-Rimkienė, Loreta; Šepić, Jadranka

doi: 10.1007/s00024-024-03596-9pmid: N/A

This study examines the impact of storm surges, infragravity waves, wider area seiches and natural harbour oscillations (harbour seiches) on port operations in the Baltic Sea, with a particular emphasis on the Port of Klaipėda, all during the severe storm that occurred from November 22–24, 2023. The study examines the interplay between meteorological factors, such as changes in air pressure and wind speed and direction, and the coastal geography of the area. Wind speeds during the storm reached a maximum of 29.7 m/s, and air pressure dropped for f ~ 50 hPa, with a corresponding sea level rise of approximately 40 cm due to the combined effects of storm surges and long waves. The research findings indicate that it was precisely long waves, which were generated offshore and amplified by the port's distinctive resonance characteristics and coastal topography, that were the primary cause of operational disruptions, creating hazardous conditions that necessitated the closure of the port. The port's elongated and narrow inlet played a pivotal role in the amplification of these waves, rendering it particularly vulnerable to resonance-induced oscillations. The research yielded several key findings, including identifying long waves (long ocean waves, wider area seiches, harbour seiches, and infragravity waves) with periods ranging from 12 to 13 h to 2–4 min, which posed significant risks to vessels moored at the port. Furthermore, the occurrence of simultaneous sea level fluctuations between Klaipėda and Karlshamn indicated the presence of seiches with period of 12,4 h across the Baltic Sea, thereby further complicating port operations. These results underscore the critical need for improved forecasting and mitigation strategies to enhance the safety and efficiency of port activities during severe weather events.

Zhou, Wenna; Tang, Hai; Chan, Yongkang; Zhang, Dailei; Xu, Bohu; Wu, Yunmeng; Li, Qiang

doi: 10.1007/s00024-024-03615-9pmid: N/A

Curie depth plays an important role in the study of geological structures and resource exploration. Conventional methods usually employ a fixed window size for estimation, often resulting in significant inaccuracies. To overcome this deficiency, a new adaptive window Curie depth calculation approach is proposed, which can automatically select the optimal window size across a range of diverse geological conditions to achieve a more precise Curie depth. We validated the new approach using synthetic data, demonstrating that the average error of the bottom depth of the model was reduced compared to traditional methods. Subsequently, we applied the new method to real magnetic data from the South China Block, and a new Curie depth result was obtained and verified using measured ground heat flow data. The mean square error between the derived results and the measured ground heat flow was found to be lower than that of the Curie depth inversed by previous researchers. The adaptive window Curie depth calculation method presented herein exhibited high adaptability and accommodated various geological features. For the South China Block, the Curie depths exhibited a smooth and continuous pattern in stable regions such as cratons, while displaying a distinct uplift in the junction region between fault zones and blocks. This method can not only accurately capture the Curie depth variations across large areas, but also vividly highlight subtle changes in the Curie depth within smaller regions, demonstrating the superiority of this new approach.

Liu, Shuangqing; Song, Zhiping; Zhang, Xiao; Chang, Liu; Wang, Lichan; Chen, Song; Xue, Yan; Wang, Yixi

doi: 10.1007/s00024-024-03594-xpmid: N/A

In recent years, new groundwater conservation policies in the Beijing-Tianjin-Hebei region have led to a rapid increase in groundwater level and a synchronous decrease in geo-electrical resistivity (GER) around Tianjin. In constrast, during the few years preceding the 1976 Tangshan M7.8 earthquake, both groundwater levels and GER around Tianjin decreased synchronously. This significant contrast seems to indicate that abnormal GER changes in Tianjin and Tangshan before the M7.8 earthquake may serve as seismogenic precursors. Therefore, in this paper, we employ combined hard inclusion models to quantitatively calculate the body strains preceding the M7.8 earthquake, and analyze their relationship with GER decreases. So far in this field, very few researches have performed theoretical calculations on the definite parameters such as the size, elastic modulus, and spatial attitude of the rheological hard inclusions, which can reasonably explain the distribution of ground deformation and seismic gaps in Tangshan and surrounding areas, as well as the asynchronous and unequal rate of GER decline. The calculation results indicate that for the 1976 Tangshan earthquake, the distribution and evolution of the precursor can be well studied by setting three ellipsoidal rheological hard inclusions with different elastic moduli through aftershock distribution. This work provides a valuable case for applying hard inclusion theory to the medium-term and short-term evolution of other strong earthquake.

Lyakhovsky, Vladimir; Mendecki, Aleksander J.

doi: 10.1007/s00024-024-03603-zpmid: N/A

Rupture dynamics along a relatively wide fault zone intersecting an underground tunnel is studied in the framework of recently developed damage-breakage rheological model. The propagating rupture produces rock damage and granulation in the process zone ahead of the rupture front, where intense torsion is simulated. It also produces an out-of-fault damage zone, of which the volume is calculated and compared with analytical predictions using the point source approximation. Interaction between propagating rupture and tunnel significantly enhances stresses around the tunnel leading to its failure with significant implosive component. Tunnel failure may occur with a certain delay after the rupture front passed, depending on the initial tunnel strength. This time delay is defined by the time needed to accumulate damage in the rock mass around the tunnel. In some cases such tunnel failure maybe interpreted as an independent implosive seismic event. Model results provide an insight into the near- and intermediate fields of seismic radiation produced by seismic sources close to and intersecting an underground tunnel. Energy dissipation in the process zone in front of the propagating rupture due to the damage–breakage mechanism significantly affects the S-wave radiation in the direction of the rupture propagation. On top of that the tunnel failure process, especially if it is surrounded by relatively weak and damaged rock, significantly reduces S-wave radiation also in the directions normal to the fault zone.

Sato, Haruo; Shiomi, Katsuhiko

doi: 10.1007/s00024-024-03600-2pmid: N/A

For the statistical characterization of the random heterogeneity of the solid earth medium, we have measured the distribution of fractional fluctuations of well log data after removing the slowly varying background variation. The well log data used are P- and S-wave velocities and mass density acquired in Japan: three data sets for the thick sedimentary layers of the Kanto Plain and two data sets for the Kujyu volcanic area of Kyushu. The estimated kurtosis is much greater than 3 for most cases, which is difficult to explain with a normal distribution. This suggests that the random fluctuations should be looked at from a broader perspective. We note the fact that the generalized central limit theorem leads to stable distributions, which are broad enough to include normal and Cauchy distributions as special cases. When the stable, normal, and Cauchy distributions are applied to the histograms of the observed fractional fluctuations, the stable distribution is found to be the most appropriate among the three distributions in most cases, where the stability parameter α\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\alpha$$\end{document} ranges from 1.5 to 2. These case studies demonstrate that the stable distribution faithfully describes the thick tails of the observed fractional fluctuations as the result of a geological sedimentation process without removing them as outliers.

Shlykov, Arseny; Schoettle, Stefan; Saraev, Alexander; Bobrov, Nikita; Tezkan, Bülent; Smirnova, Maria; Yogeshwar, Pritam

doi: 10.1007/s00024-024-03478-0pmid: N/A

In the controlled source radiomagnetotelluric (CSRMT) sounding method, different types of sources are in common use. However, no systematic examination of their advantages and disadvantages exists. In this paper, we analyze the electromagnetic fields of different CSRMT sources: horizontal electric dipole, HED, horizontal magnetic dipole, HMD, and vertical magnetic dipole, VMD, using both numerical modelling and field data. Positions of the boundary between the far-field and transition zones have been determined. Using 1D and 2D modelling and results of field experiments, we have shown that the HMD source has the smallest transition zone, while the VMD source has the largest one. In general, the HMD and HED sources are preferred for soundings in the far-field zone, due to the versatility of the transmitter’s geometry, and to the possibility of tensor measurements and use of 2D-3D magnetotelluric codes for data interpretation. In the case of the homogeneous half-space, for all sources the boundary between the transition and the far-field zone is farther away from a source for the impedance phase than for the apparent resistivity. Comparison of the signal magnitudes’ decay indicates that the field from the VMD source shows the slowest decrease with distance in the transition zone, while the field from the HMD source shows the fastest decrease, confirming the shorter range of measurements using the latter source. Using field experiments, we have compared the magnitudes of HED-, VMD-, and HMD-signals at odd subharmonics relative to the signal magnitude at the main frequency. We find that use of a HED source has definite advantage over loop sources for broadband frequency measurements with the square waveform from transmitter.

Soledade, André; da Silva Neto, Antônio José; Moreira, Davidson Martins

doi: 10.1007/s00024-024-03580-3pmid: N/A

Nowadays, several applications in engineering and science are considering fractional partial differential equations. However, this type of equation presents new challenges to obtaining analytical solutions, since most existing techniques have been developed for integer order differential equations. In this sense, this work aims to investigate the potential of fractional derivatives in the mathematical modeling of the dispersion of atmospheric pollutants by obtaining a semi-analytical solution of the time-dependent fractional, two-dimensional advection–diffusion equation. To reach this goal, the GILTT (Generalized Integral Laplace Transform Technique) and conformal derivative methods were combined, taking fractional parameters in the transient and longitudinal advective terms. This procedure allows the anomalous behavior in the dispersion process to be considered, resulting in a new methodology called α-GILTT. A statistical comparison between the traditional Copenhagen experiment dataset (moderately unstable) with the simulations from the model showed little influence on the fractional parameters under lower fractionality conditions. However, the sensitivity tests with the fractional parameters allow us to conclude that they effectively influence the dispersion of pollutants in the atmosphere, suggesting dependence on atmospheric stability.

Menke, William

doi: 10.1007/s00024-024-03581-2pmid: N/A

We adapt the Metropolis–Hastings (MH) algorithm to facilitate construction of the ensemble solution of the nonlinear implicit inverse problem. The solution variable is the aggregation of the parameters of interest (model parameters) and the data. The prior probability density function (pdf) is the possibly-non-Normal joint pdf of the prior model parameters and the noisy data, and is defined in a high-dimensional space. The posterior pdf of the solution (estimated model parameter and predicted data) is the prior pdf evaluated on the lower-dimensional manifold defined by the theory. We adapt the MH algorithm to ensure that successors always satisfy the theory (that is, are on the manifold) and provide a rule for computing the probability of a given successor. Key parts of this adaption are the use of singular value decomposition to identify subspaces tangent to the manifold, and orthogonal projection, to move a preliminary estimate of a successor onto the manifold. We apply the adapted methodology to three exemplary problems: fitting a straight line to (x,y) data, when both x and y have measurement noise; fitting a circle to noisy (x,y) data, and finding a filter that takes one noisy time series into another. In these cases, the scatter of the ensemble solution about the linearized maximum likelihood solution is roughly consistent with the linearized posterior covariance, but with some non-Normal behavior. We demonstrate the usefulness of the ensemble solutions by computing empirical pdfs of several informative statistical parameters, the calculation of which would be difficult by traditional means.

Netto, Leonides Guireli; Moreira, César Augusto; Bianchi, Henrique Marquiori; Gandolfo, Otávio Coaracy Brasil; Ilha, Lenon Melo

doi: 10.1007/s00024-024-03602-0pmid: N/A

The challenges inherent in mining environmental liabilities, especially in radioactive mineral contexts, highlight the crucial importance of rehabilitating and properly managing degraded areas and tailings. In radioactive minerals mining, the challenges are accentuated due to the complexity of the materials and the environmental risks associated with persistent radioactivity. This scenario underlines the critical need for precise environmental management strategies, highlighting the importance of geophysical techniques for monitoring and mitigating environmental risks in radionuclide retention ponds. Geophysical techniques, such as electrical tomography and seismic tomography refraction, are interesting tools for identifying anomalies in the subsoil, such as leaks, fractures and contamination zones, which are not visible on the surface. These methods provide a non-invasive means of continuously monitoring the integrity of tailings storage facilities, allowing for early detection of potential failures or contamination pathways. By offering a more spatial understanding of subsurface conditions compared to traditional geotechnical instrumentation, geophysics plays an important role in mitigating environmental impacts, reducing risks to nearby ecosystems and informing rehabilitation efforts in radioactive mineral mining areas. This study applied electrical and seismic methods to assess two retention ponds at a uranium mine, demonstrating how these techniques can help in the safe decommissioning of mining facilities and the sustainable management of environmental liabilities. With a focus on two retention ponds of a uranium mine in South America in the process of decommissioning, the results revealed conductive electrical anomalies and variations in the geological layers identified by electrical tomography and refraction seismic, respectively, indicating potentially contaminated areas and alterations in the degree of fracturing of the foundation rock of the ponds. Comparing these results with a structural survey of fracture orientations in the study area demonstrates the preferential path of underground flow, conditioned by the fracturing pattern of the weathered rocks. These findings emphasize the importance of geophysics in the decommissioning phase of nuclear facilities, not only to monitor stored environmental liabilities, but also to assist in the recovery of degraded environments in the proximity of the mines.