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The Guxiang–Tongmai segment of the Jiali fault is situated northeast of the Namche Barwa Syntaxis in northeastern Tibet. It is one of the most active strike‐slip faults near the syntaxis and plays a pivotal role in the examination of seismic activity within the eastern Himalayan Syntaxis. New study in the research region has yielded a 1:200000 gravity dataset covering an area 1500 km2. Using wavelet transform multiscale decomposition, scratch analysis techniques, and 3D gravity inversion methods, gravity anomalies, fault distributions, and density structures were determined across various scales. Through the integration of our new gravity data with other geophysical and geological information, our findings demonstrate substantial variations in the overall crustal density within the region, with the fault distribution closely linked to these density fluctuations. Disparities in stratigraphic density are important causes of variations in the capacity of geological formations to endure regional tectonic stress. Earthquakes are predominantly concentrated within the density transition zone and are primarily situated in regions of elevated density. The hanging wall stress within the Guxiang–Tongmai segment of the Jiali fault exhibits a notable concentration, marked by pronounced anisotropy, and is positioned within the density differential zone, which is prone to earthquakes. [ABSTRACT FROM AUTHOR]

The Zafra de Záncara anticline (also known as the El Hito anticline), located in the Loranca Cenozoic Basin (part of the Tagus Basin, Central Spain), had been studied by several oil companies during the late 1960s and early 1970s. In 2009, within the 'Plan for selection and characterization of suitable structures of CO2 geological storage', this anticline was selected as a potential CO2 storage site. A preliminary three‐dimensional geological model, based on five geological cross sections that were constrained with the interpretation of the available seismic profiles (that are rather old and do not have very good quality), was created. With the aim of improving the geological knowledge of the Zafra de Záncara anticline and helping to investigate the suitability of a nearby anticline, namely La Rambla, as another structural closure that might make it a possible CO2 storage site, a local gravity survey (1 station every km2) was carried out in the area, seven new geological cross sections, based on these existing seismic profiles and field geology, were build, and a new three‐dimensional geological model that included both anticlines, improved through three‐dimensional stochastic gravity inversion, was constructed. The densities needed for the geological formations of the model come from the analysis of rock samples, logging data from El Hito‐1 drillhole and petrophysical information from Instituto Geológico y Minero de España database. The inversion has improved the knowledge about the geometry of the anticlines' traps and seals as well as the geometry of the basement relief and the structural relationship between basement and cover. [ABSTRACT FROM AUTHOR]

The past few years have witnessed significant advances and unparalleled interest in gravity gradiometer instrument technology as well as new deployment scenarios for various applications. Gravity gradiometry is now routinely considered as a viable component for resource exploration activities as well as being deployed for global information gathering. Since the introduction of the torsion balance in the 1890s, it has been recognized that gravity gradient information is valuable – yet difficult and time-consuming to obtain. The recent acceptance and routine use of airborne gravity gradiometry for exploration has inspired many new technology developments. This paper summarizes advances in gravity gradient sensor development and also looks at deployment scenarios and gradiometer systems that have been successfully fielded. With projected improved system performance on the horizon, new challenges will also come to the forefront. Included in these challenges are aspects of instrument and system intrinsic noise, vehicle dynamic noise, terrain noise, geologic noise and other noise sources. Each of these aspects is briefly reviewed herein and recommendations for improvements presented. [ABSTRACT FROM AUTHOR]

This contribution aims to discuss how gravity-driven processes affect the archaeological record with the goal of building a broad conceptual and methodological framework for dealingwith these contexts. A wide compilation of cases regarding gravity-driven processes is analyzed to recognize relevant environmental factors, the way they affect the properties of the record, and long-term archaeological expectations. Only by understanding the specific mechanisms and processes that occur in each context can an accurate methodological approach be chosen on which to base interpretations. A careful taphonomic study of the spatial distribution, frequency, size, diversity, and orientation of materials comprising the archaeological record is the first step to recognizing formation processes. Actualistic studies provide a framework for discussing the timing and intensity at which processes occur. A detailed geomorphological description is required to interpret sedimentological and micromorphological analysis, which in turn helps understanding of the relative subaerial permanence of the record, its temporal resolution, and preservation potential. Interpreting surface and buried materials requires the understanding of pedogenetic processes. Broad in/off-site spatial sampling strategies definitely yield a more realistic picture about the variety of processes in slope settings. [ABSTRACT FROM AUTHOR]

Gravimetric techniques are used for monitoring the distribution and migration of CO2 stored in geological formations. Superconducting gravimeters (SGs), because of their high sensitivity, can enable continuous ground‐based monitoring of offshore CO2 storage. For offshore monitoring purposes, gravity stations should be located near the seashore to maximize the signal of interest. We observed gravity continuously with an SG near the seashore at the Tomakomai carbon dioxide capture and storage demonstration site in Japan to assess variation of the observed gravity and to evaluate the applicability of this technique for monitoring of large‐scale offshore storage. Strong noise caused by strong winds and ocean waves was removed by low‐pass filtering. The noise did not fundamentally affect long‐term gravity changes. The observed gravity was affected strongly by shallow groundwater level changes but the effects were sufficiently corrected by expressing their effects as a summation of linear functions of groundwater level changes. Considering all possible effects on gravity, the standard deviation of the gravity residuals during 85 days of observation was minimized to 7.5–8.2 nm s–2. Based on the model setting of the Tomakomai site, the estimated annual gravity changes caused by industrial‐scale injection (1 MtCO2 year–1) into a hypothetical offshore formation (1 km depth) were –2.8 to –3.3 nm s–2 under different saturation conditions. The estimated changes exceed the observed standard deviation in 2.3–2.9 years. These results suggest that injection‐induced gravity changes can be detected using SG within a few years. Therefore, the present ground‐based gravimetric technique can contribute to long‐term monitoring of offshore storage. © 2019 Society of Chemical Industry and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The Central‐Eastern Mediterranean region is known to be a complex area due to the interaction of four tectonic plates, namely Arabia, Africa, Anatolia and Eurasia, and by the presence of an ancient oceanic crust in the Herodotus and Ionian Basins. The analysis of the available literature highlights that the distribution of the freely available geophysical data (i.e. seismic, gravity and magnetic observations) is quite disparate. In this framework, high‐resolution global gravity field models, such as XGM2019e, mainly based (offshore) on satellite data, can be profitably used as a uniform dataset to study, in a coherent way, large regions. In the current work, we exploit the XGM2019e model, together with a set of a priori information, derived mainly from geophysical data retrieved from the literature, to study the structure of the crust in the Central‐Eastern Mediterranean area. The study is organized in three different phases: in the first one, we enhanced the map of geological crustal provinces by means of an automatic Bayesian classification algorithm applied to the second radial derivatives of the gravitational potential. In the second phase, using as observation a grid of gravity anomalies, we applied a full three‐dimensional inversion procedure (always based on a Bayesian paradigm) to estimate the mass density variations and the geometries of the main geological units in the whole study area. Finally, in the third phase, we performed a refined three‐dimensional local inversion on the Cyprus area to improve the modelling of the shallowest layers. The main results of this study, carried out in the framework of the European Space Agency GIADA project, are freely available, upon request, at https://www.g‐red.eu/geophysics/. [ABSTRACT FROM AUTHOR]

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 for salt and other mines in Colombia, very little data on the internal structure and geology are publicly available. The purpose of our study is to show how gravity data and modelling can be used to infer near‐surface properties above the mine in the absence of other sources of information. Relative gravity measurements were made over an irregular grid of 107 stations and tied to the Instituto Geográfico Augustin Codazi national absolute gravity network. The total and residual Bouguer anomalies as well as the analytic signal were calculated over the area of the salt body. Using grid data, we first determine the main inversion parameters (e.g., depth weighting) and model resolution using a checkerboard model with the addition of random noise. Then, applying 3D inversion modelling to the residual Bouguer anomaly, we find that the positive and negative anomalies correspond to few zones of positive density contrasts and two main zones of negative density contrasts. Some of the positive anomalies are located above the fault trace putting in contact the Arenisca Dura formation with the Conejo formation containing the salt body. The negative anomalies are not well correlated with the underground position of the salt mine, but some influence of the low‐density 'rute' material, consisting of black clays with shaly claystone parts covering the salt body might be important. This study showcases how 3D inverse modelling can provide important information on the near‐surface structure of a salt mine. [ABSTRACT FROM AUTHOR]

Geological interpretation based on gravity gradiometry data constitutes a very challenging problem. Rigorous 3D inversion is the main technique used in quantitative interpretation of the gravity gradiometry data. An alternative approach to the quantitative analysis of the gravity gradiometry data is based on 3D smooth potential field migration. This rapid imaging approach, however, has the shortcomings of providing smooth images since it is based on direct integral transformation of the observed gravity tensor data. Another limitation of migration transformation is related to the fact that, in a general case, the gravity data generated by the migration image do not fit the observed data well. In this paper, we describe a new approach to rapid imaging that allows us to produce the density distribution which adequately describes the observed data and, at the same time, images the structures with anomalous densities having sharp boundaries. This approach is based on the basic theory of potential field migration with a focusing stabilizer in the framework of regularized scheme, which iteratively transfers the observed gravity tensor field into an image of the density distribution in the subsurface formations. The results of gravity migration can also be considered as an a priori model for conventional inversion subsequently. We demonstrate the practical application of migration imaging using both synthetic and real gravity gradiometry data sets acquired for the Nordkapp Basin in the Barents Sea. [ABSTRACT FROM AUTHOR]

An extensive experimental study was performed to investigate the effect of various parameters such as temperature, pressure, and crude oil API gravity on the fluid interactions in the binary systems of brine‐CO2 and two heavy oil‐CO2 systems. The solubility of CO2 in 20 000 ppm brine solution was measured at various experimental conditions. The solubility of CO2 and swelling factor, due to the CO2 dissolution, of two heavy crude oil samples (type‐I: °API = 20.44 and type‐II: °API = 15.49) were experimentally measured at various operating conditions. Results showed that the solubility of CO2 in heavy oil increased when the experimental pressure increased, and when the experimental temperature decreased. At a constant pressure of Pexp = 3.44 MPa, the solubility of the CO2 was measured to be 10.13, 5.72 g CO2/100 g oil in the type‐I crude oil when the temperature increased from T = 21 to 45 °C. Increasing the experimental pressure from Pexp = 1.38 MPa to 3.44 MPa at a constant temperature of T = 21 °C increased the solubility of the CO2 from 2.37 to 7.84 g CO2/100 g oil in the type‐II crude oil. The reduction in the oil API gravity had an adverse effect on the CO2 solubility. At a temperature of T = 21 °C and a pressure of Pexp = 3.44 MPa, the CO2 solubility decreased from ∼10.13 in the type‐I oil to 7.84 g CO2/100 g oil in the type‐II oil. The measured values of the swelling factor showed that the type‐I and type‐II crude oils could exhibit a maximum swelling factor of 1.079 and 1.052 at a temperature of T = 21 °C and a pressure of Pexp = 3.44 MPa. [ABSTRACT FROM AUTHOR]

This numerical study focuses on the inversion of the CO2 plume shape and stored mass amount from both surface and borehole time-lapse gravity simulated measurements in saline aquifers. Solving for the density distribution at depth and hence the shape of the plume is an ill-posed inverse problem which requires regularization. We opt for regularized least-square inversion, using both L-Curve and general cross validation methods to obtain the regularization parameter. Numerical inversion experiments are set up by modeling the spatial distribution of injected gaseous CO2 using a 1D radial transport model, which allows testing for both injected mass amount and injection depth. We find that including surface data alone, the error on the position of the inverted plume is of the order of ∼30% for the shallowest aquifer depths of 800 to 1200 m and for injected CO2 mass larger than 10 Mt. The positioning error increases as depth increases and injection mass decreases. The addition of measurements from a single borehole to surface measurements, though stabilizing the inversion, only reduces the error on the position by a mere 5%. However, while the positioning error is high, the real CO2 mass within the inverted CO2 plume area is close to the total injected CO2 mass, with more than 90% of the injected mass being captured using surface and borehole data with the L-Curve method. This relatively high mass ratio shows that this method can be used to detect the main bulk of the injected CO2 plume. © 2015 Society of Chemical Industry and John Wiley & Sons, Ltd [ABSTRACT FROM AUTHOR]