A combination of electrical resistivity tomography (ERT) and magnetic gradiometry was selected to examine a hypothesis concerning the presence of remains of one of the oldest archaeological churches in the Rhineland, located in Neuss-Norf, Germany. The gradiometer survey was carried out to measure the vertical gradient of the magnetic field using a proton precession magnetometer along several profiles

ABSTRACT The physical parameter found from inversion of EM surveys: the distribution of subsurface conductivity, is interesting in itself only in very few instances. In most cases the conductivity distribution will have to be interpreted in terms of the target properties of the survey, e.g. a geological interpretation of lithology, a hydrogeological interpretation of hydraulic conductivity, a biohazard/geotechnical

Glacial ice from the last major advance covered the state of Connecticut and reached its glacial maximum on Long Island ∼21,000 years ago. As glacial ice melted and retreated northward, meltwater streams deposited sediments, like gravel, sand, silt, and clay, in low-lying areas. Many periglacial lakes formed in central Connecticut as meltwater accumulated into valleys that were dammed by ice or glacial

The Khorat plateau covers most of northeast Thailand along with parts of southern Laos. Recent earthquake hazard assessment and other studies of the regional Thakek fault have rarely appeared in publications and reports. The Thakek fault zone in the Laos region includes three main principal fault planes, but it rapidly fades out when the fault passes through Thailand. A geophysical hidden fault study

Lutetian limestones have been widely used in historical monuments within the Paris Basin during the course of the medieval and modern periods. Among the physical properties that can be used to assess the evolution of the limestones in situ in the buildings and their present health, the complex effective permittivity in the 10–100 kHz frequency range is easy to measure and reflects the internal structure

Sensitive glaciomarine clays, often referred to as ‘quick clay’, commonly occur in many countries at high, northerly latitudes, causing frequent and occasionally devastating landslides. The salt content of quick clay is strongly correlated to both its shear strength and electrical resistivity. Hence, it can be mapped using electromagnetic methods more efficiently than traditional intrusive methods

Spatial planning aims at constantly improving the distribution of people and activities within available space, especially near cities on ancient agricultural or industrial areas. However, a proper schedule of the development work necessitates the assessment, as precisely as possible, of the difficulties that would be encountered in terms of geotechnical abilities of the terrain and hazards resulting

Surface-wave inversion is a non-linear and ill-conditioned problem usually solved through deterministic or global optimization approaches. Here, we present an alternative method based on machine learning. Under the assumption of a local one-dimensional model, we train a residual neural network to predict the non-linear mapping between the full dispersion image and the model space, parameterized in

Wave-equation traveltime inversion (WTI) can be used to automatically obtain a background near-surface velocity model (NSM), which overcomes the high-frequency approximation in ray theory. It is generally implemented in the time domain. However, the commonly used gradient-based optimisation methods (such as the steepest-descent method) in WTI have a low convergence rate and may yield less accurate

Electromagnetic instrument responses suffer from signal drift that results in a variable response at a given location over time. If left uncorrected, spatiotemporal aliasing can manifest and global trends or abrupt changes might be observed in the data, which are independent of subsurface electromagnetic variations. By performing static ground measurements, we characterized drift patterns of different

The evaluation of groundwater presence by means of seismic wave velocities is of great concern for many hydrological related engineering applications. This work introduces a simple basic procedure to accurately and systematically identify groundwater levels using P-wave and S-wave velocities. This procedure is defined as a seismic reflectivity parameter and based on the seismic reflection coefficients

The existence of active faults hidden below Quaternary alluvium is a common geological scenario for intermontane basins, such as the areas struck by the recent earthquakes in Central Italy, and is of great importance for seismic hazard evaluation. Finding hidden faults is a challenging task from the geophysicist's point of view since the goal is twofold: to identify the seismic bedrock at a certain

The city of Pohang in South Korea experienced substantial damage following the ML 5.4 earthquake on 15 November 2017. Damage surveys immediately after the earthquake revealed significant spatial variations in damage intensity across the epicentral area. We collected ambient noise data (three‐component seismic data) from 124 locations in Pohang, covering a total area of 17 km × 20 km, and applied the

An electrical resistivity tomography survey was conducted to assess the subsurface conditions associated with the coseismic liquefaction phenomenon in the epicentral region following the Mw 5.8 Mirpur earthquake (Pakistan) on 24 September 2019. The Mirpur earthquake produced extensive coseismic liquefaction‐induced surface deformations, including: sand blows, ground failure and lateral spreading along

The Gadora village landslide zone situated along National Highway 58 has become very active in recent years. The landslide zone is causing a lot of damage to property along the highway and endangering the lives of people living uphill and downhill of the slopes. In the present study, a combined geological, geophysical and geotechnical investigation has been carried out to establish the subsurface layering

On El Hierro (Canary Islands, Spain), the company Gorona del Viento El Hierro S.A. carried out the construction of a Wind‐Pumped Hydro Power Station in order to achieve the energy autonomy on the island through 100% renewable energy. The station consists of two man‐made water reservoirs, whose design was adapted to the island topography and emplaced in a valley and an inactive crater. In order to study

In the past decade, passive seismic methods have shown the possibility to detect significant changes in surface wave velocity up to several days prior to landslide failure, even with sensors located outside the unstable zone. Electrical resistivity tomography has also long been used to monitor hydrological changes in landslides. However, the displacement of electrodes relative to each other during

The warming of rock permafrost affects mechanical stability and hydro‐cryostatic pressures in rock walls. The coincident decrease in slope stability frequently affects infrastructure by creep and subsidence and promotes the generation of rockfalls and rockslides. The increasing hazard posed by warming permafrost rock walls and the growing exposure of infrastructure and individuals create a demand for

Palaeoseismology studies the footprints of ancient earthquakes to improve the knowledge about the modern seismicity of the territory. A ground‐penetrating radar (GPR), among other geophysical methods, is used for quick determination of shallow stratigraphy – displaced, oblique layers within the fault zone. GPR data interpretation from diverse and complex reflection patterns of the fault zone heavily

We introduce an algorithm to monitor seismic velocity changes associated with rockbursts in mines, through microseismic monitoring. Rockbursts are extreme events resulting from the complex interaction between mining activities and geology, and represent a significant threat to mines. In recent years, the use of passive seismic monitoring for mine safety and productivity has progressed substantially

In the last decade, time-domain crosshole ground-penetrating radar full-waveform inversion has been applied to several different test sites and has improved the resolution and reconstruction of subsurface properties. The full-waveform inversion requires several diligent executed pre-processing steps to guarantee a successful inversion and to minimize the risk of being trapped in a local minimum. Thereby

A gravity survey was conducted at a salt mine in Nemocón, Cundinamarca, Colombia, located in the axial part of the Eastern Cordillera of the northern Andes. This part of the Eastern Cordillera is characterized by successions of synclines and anticlines sometimes containing salt bodies at their core, and the mine is located at the top of one of these anticlines called the Nemocón anticline. As is typical

The combination of geophysical surface‐based imaging techniques, including seismic and electrical resistivity tomography (ERT), is now common practice to obtain a more accurate characterization of subsurface structures. Due to model non‐uniqueness and geological heterogeneity, conventional travel‐time tomography cannot solely reveal hidden layers (i.e., low‐velocity zones embedded between layers of

Seismic surveys were performed using a novel application of combined active and passive surface wave methods to evaluate the integrity of levees protecting islands in the Sacramento–San Joaquin Delta, California, USA, from flooding. Delta islands have been undergoing rapid subsidence during the past century due to farming practices that have led to the loss of a surficial peat layer. A large earthquake

The influence of rainfall on the Pakhi landslide has been examined using a pre‐ and post‐monsoon timelapse electrical resistivity imaging technique. The results obtained have been used to characterize the subsurface based on the depth and degree of water seepage and degree of weathering. The combined interpretation of pre‐ and post‐monsoon electrical resistivity tomography is not very common in landslide

Examples of the application of microgravity mehtod for the detection of potentially hazardous (empty) underground cavities caused by the collapse of coal mines are presented. Within these areas some alteration by previous remediation activity had occurred. This was not documented earlier and, therefore, such alteration was often unknown prior to the current investigations. We show a successful application

A new technique is proposed to level airborne geophysical data based on the assumption that the level errors along the flight‐line direction have a distinguishable centre frequency. In the levelling method, airborne geophysical data from the entire survey area are corrected automatically after sorting the data into a group according to the measurement order. Variational mode decomposition is applied

Full‐waveform inversion has proved to be an effective and robust approach for near‐surface site characterization. Past full‐waveform inversion studies have mostly focused on Rayleigh wave, with only a few studies focussing on SH‐ and Love‐waves. Compared with Rayleigh waves, the main advantages of using SH‐ and Love‐waves are that they are more sensitive to mass density of materials and require much

This paper underscores the importance of spatially dense geophysical data sets for making informed decisions in water management strategies. Such decisions may require understanding how site‐specific subsurface architecture – especially hydraulic connectivity – impacts the response of a shallow aquifer to anthropogenic hydrologic disturbances (e.g. over‐pumping of a shallow aquifer). At a 0.2‐km2 alluvial

Renovation of water and central heating pipelines is a very costly and time‐consuming process; therefore, a way to prioritize the limited resources between different parts of the systems is very important. The risk for corrosion damage can be assessed from the resistivity of the ground, because the processes facilitating the metal oxidation also affect the resistivity. However, galvanic resistivity

Electrical resistivity tomography is an ill‐posed and nonlinear inverse problem commonly solved through deterministic gradient‐based methods. These methods guarantee a fast convergence towards the final solution, but the local linearization of the inverse operator impedes accurate uncertainty assessments. On the contrary, numerical Markov chain Monte Carlo algorithms allow for accurate uncertainty

Reverse time migration can accurately image underground earth structures. However, for shallow seismic exploration, the seismic wave velocity is often lower than the velocity in the middle‐deep layers, which causes numerical dispersion for finite‐difference schemes and leads to poor seismic imaging quality. Suppressing numerical dispersion by grid encryption or increasing the finite‐difference order

Worldwide, soil contamination due to industrial activities is a major issue. One method for remediation of contaminated sites is in situ chemical oxidation, where an oxidizing agent is injected into the contaminated soil. Normally, monitoring wells are established in the remediation area for tracking the oxidizing agent. However, wells only provide point information of the injectant spread. This issue

During metro construction, unidentified cavities pose a serious threat to the integrity of the tunnels and public safety. An efficient and accurate cavity‐detection method is needed, given the limited space and time constraints of urban construction. Equivalent offset migration is a high‐accuracy, seismic scattered‐wave imaging method that is effective in wavefield extraction, has the ability to derive

For transient electromagnetic inversion, a gradient‐based algorithm is strongly dependent on the quality of the initial model, while any non‐gradient‐based algorithm often falls too easily into local optima. This paper proposes a joint differential‐evolution–particle‐swarm‐optimization inversion algorithm, which provides a better global optimization. A dual‐population evolution strategy and information

ABSTRACT This study presents results of ground‐penetrating radar surveys conducted for the exploration of unexcavated tombs at the Kharga Oasis. These surveys were carried out on two ancient tombs. The first site, located in Labakha, is already excavated, while the second site, located in Gebel El‐Siwa, is still unexcavated. The goal of this study was to investigate the possibility of the existence

ABSTRACT The inversion of active surface‐wave data is highly affected by the non‐uniqueness of the solution. While a deterministic approach is generally chosen due to certain advantages, there is the risk of getting trapped in a local minima, especially when no a priori information is available about the sub‐surface geometry since the layer thickness is assumed fixed to a priori. The fixed‐layer thickness

ABSTRACT In this paper, we propose an enhanced version of the multi‐gradient measurement technique, called full‐range gradient survey, for 2D electrical resistivity tomography. To demonstrate its effectiveness, we conducted numerical simulations and field experiments to highlight the advantages of the new data‐acquisition technique on the traditional electrode arrays and the original multi‐gradient

The Garhwal–Kumaun region of the Himalaya encompassing the state of Uttarakhand, India, has experienced several earthquakes in the past. Damage due to earthquakes is controlled by local site conditions, primarily resonance frequency and wave amplification from the ground. We present local site parameters with their site geology for 37 sites using ambient noise data. Horizontal to vertical spectral

ABSTRACT Migration is considered to be a key step in the data processing of the seismic advancement predictions of tunnels, and it directly affects the final interpretations. Therefore, with the goal of addressing the limitations of the current acoustic reverse‐time migration processes, as well as deepening the understanding of the interactions between different wave modes in traditional elastic reverse‐time

ABSTRACT Various methods were earlier designed to calculate porosity of a formation, but many of them are reliant on physical soil sampling and/or laboratory measurements. The present work examines a recently proposed method, which we call here as Sample‐free Porosity Calculation from Resistivity Imaging Data (SPyCRID), to calculate porosity of unconsolidated soils. By conjoining Archie's and Waxman–Smits’

ABSTRACT A novel traveltime tomographic approach is applied to anisotropic media, limited to 2D geometry at present. A general anisotropic Eikonal solver based on a discontinuous Galerkin method is combined with an efficient adjoint formulation for multiparameter least‐squares inversion. This new approach is tested considering synthetic crosshole ground‐penetrating radar data. The configuration of

ABSTRACT In this study, we undertake a renewed investigation of up‐bent reflections seen in seismic time sections from the Baltic Sea, Bay of Kiel. These warped reflections stretch over the entire vertical extent of the sections, from Permian to Quaternary strata, and underlie tunnel valleys. Previous studies interpreted these structures as anticlines, explaining them together with adjacent faults

ABSTRACT Downhole nuclear magnetic resonance technology was applied in four boreholes intersecting glaciomarine sediments of the Ottawa Valley, Ontario. The study evaluated the ability of slim‐hole nuclear magnetic resonance tools to measure in situ volumetric water contents (porosities in saturated sediments) for geohazard and hydrogeological applications. The sediments are composed of clay‐ and silt‐sized

ABSTRACT A major problem for the freshwater supply of coastal regions is the intrusion of saltwater into aquifers. Due to extensive extraction of freshwater to suffice increasing drinking water demands and/or in periods of reduced groundwater recharge, the equilibrium state may be disturbed. The result is an upconing or movement of the fresh–saline groundwater interface, which reduces the local drinking

In the past several decades, there has been considerable interest in groundwater-surface water interactions and their ability to regulate and cycle nutrients and pollutants. These interactions are spatially and temporally complex; however, electrical resistivity imaging can be a useful tool for their characterization. Here, an electrical resistivity imaging monitoring array was installed laterally

ABSTRACT Over the past 20 years, there has been growing interest in the use of the subsurface for water storage using shallow ponds, where water is infiltrated to the subsurface and subsequently groundwater is recovered from pumping wells. This scheme is designed as a surface‐managed aquifer recharge. Llobregat artificial recharge ponds are managed aquifer recharge systems located in alluvial aquifers

ABSTRACT To improve risk assessment, control and treatment strategies of contaminated sites, we require accurate methods for monitoring solute transport and infiltration in the unsaturated zone. Highly spatio‐temporal heterogeneous infiltration during snowmelt increases the risk of contaminating the groundwater in areas where de‐icing chemicals are required for winter maintenance of roads and runways

ABSTRACT Electrical resistivity tomography is a technique widely used for the investigation of the structure and fluid dynamics of the shallow subsurface, particularly for hydro‐geophysical purposes, sometimes using cross‐borehole configurations. The results of electrical resistivity tomography inversion and their usefulness in solving hydrogeophysical problems, even though invariably limited by resolution

ABSTRACT In this paper, we discuss the necessity of quantifying and correcting seasonal 3D effects on 2D electrical resistivity tomography (ERT) data measured along the embankments of rivers or artificial canals. A permanent ERT monitoring system has been continuously operating along the levee of an irrigation canal in Mantua province, Italy, since September 2015. To evaluate the importance of 3D effects

ABSTRACT Wind turbines produce mechanical energy that can propagate to the ground and disturb sensitive measurements such as seismic recordings. The aim of the large‐scale experiment Seismic Monitoring And Research of wind Turbine Induced Emissions (SMARTIE1) at a single wind turbine in Pfinztal (SW Germany) is to understand how wind turbines emit seismic signals under different operating conditions

ABSTRACT The use of surface wave testing for near‐surface engineering applications has increased in recent years. Typical surface wave analysis is based on the dispersion of surface waves in one‐dimensional layered models. One‐dimensional models are inappropriate for measurements at sites with appreciable lateral variability, a likely scenario in many engineering applications. Use of such models can

ABSTRACT An unexpected surface subsidence in Mexico City on 19 May 2015 prompted a detailed geophysical investigation of the three‐dimensional structure of a collapsed‐soil mine located in a section of the Chapultepec Park in the vicinity of an artificial lake. As revealed from past geological explorations, the subsoil at the site consists of volcano‐sedimentary materials that were quarried in the

Several studies have explored the potential of electrical resistivity tomography to monitor changes in soil moisture associated with the root water uptake of different crops. Such studies usually use a set of limited below-ground measurements throughout the growth season but are often unable to get a complete picture of the dynamics of the processes. With the development of high-throughput phenotyping

ABSTRACT To derive reliable electrical resistivity subsurface models using error‐weighted inversion schemes, a meaningful and correct error model is required. An over‐estimated error leads to a lack of resolution and reduced target detectability. Furthermore, biased data are easily overlooked and can lead to artefacts and significant miss‐interpretation. We carried out an electrical resistivity tomography

ABSTRACT A new method is presented for the 3‐D forward modelling of the magnetic effects (induced magnetization) of a hexahedral (trilinear) prism using the Gauss–Legendre quadrature method. The 3‐D forward modelling provides an improved application to geological problems. The magnetic effect has been evaluated via the summation of the effects of the point dipole that fills the volume. The 3‐D volume

The Ripley Landslide is a small (0.04 km2), slow-moving landslide in the Thompson River Valley, British Columbia, that is threatening the serviceability of two national railway lines. Slope failures in this area are having negative impacts on railway infrastructure, terrestrial and aquatic ecosystems, public safety, communities, local heritage and the economy. This is driving the need for monitoring

ABSTRACT In this work, we describe an experiment concerning global–local full‐waveform inversion, carried out on a P‐wave seismic reflection profile that was acquired at Luni, an archaeological site in Italy. The global full‐waveform inversion makes use of a two‐grid genetic algorithm scheme and recorded refraction and diving waves, to build an initial velocity model of the subsurface. Two important

ABSTRACT To investigate transient dynamics of soil water redistribution during infiltration, we conducted horizontal borehole and surface ground penetrating radar measurements during a 4‐day infiltration experiment at the rhizontron facility in Selhausen, Germany. Zero‐offset ground penetrating radar profiling in horizontal boreholes was used to obtain soil water content information at specific depths

ABSTRACT We apply seismic full waveform inversion to SH‐ and Love‐wave data for investigating the near‐surface lithology at an archaeological site. We evaluate the resolution of the applied full waveform inversion algorithm through ground truthing in the form of an excavation and sediment core studies. Thereby, we investigate the benefits of full waveform inversion in comparison with other established