Academic literature on the topic 'Euler pole estimate'

Eastern Canada is characterized by many intraplate earthquakes mostly concentrated along the Saint Lawrence River and Ottawa River valleys. After the rigid plate rotation of North America, the glacial isostatic adjustment (GIA) is by far the largest source of geophysical signal in eastern Canada. We estimate a set of Euler pole parameters for this area using a velocity field of 19 continuously operating GPS stations out of 112, and show that they are different from the overall rotation of the North American plate. This difference potentially reflects local stresses in this seismic region, and the difference in intraplate velocities between the two flanks of the Saint Lawrence River valley accumulate stress along the river.

The new map of linear magnetic anomalies axis for the mid-Arctic ridge east areas development in the Eurasian basin is made. The domestic geomagnetic investigations for the first time allow to determine paleomagnetic anomaly C25 and estimate the time of transfer rifting to spreading process as chrons С25r-С26n (57.656-59.237 ma). The eastablishing of Lomonosov ridge and Siberian margin splitting zone is made. The Euler pole for the splitting kinematic for first time calculated. The nocoinciding of conjugate isobaths related to process of sliding peripheral continental crust areas along lithosphere thrust plane for the first time is calculate.

Spectral technique and Euler Deconvolution were applied to high-resolution aeromagnetic data of parts of Benue trough to estimate the depth of anomalous magnetic sources within the study area; Data enhancement techniques such as total magnetic intensity map, reduction to pole, regional-residual separation and upward continuation maps were employed to identify different magnetic anomalies, structural trends representing the tectonics of the location were observed trending NE-SW and N-S directions; The result of 3D Euler deconvolution for the structural index (SI) = 0, 1, 2, 3 gave depths to magnetic sources that range from -589;3 m to -2678;8 m, -459;0 m to -2691;9 m, -294;6 m to -2817;5 m, - 430;2 m to -2780;6 m respectively; The depth estimates from 2-D spectral revealed a two-layer model; The shallow magnetic depth ranges between 0;135 km to 0;200 km with a mean depth of 0;158 km and the depth to magnetic basement vary between 2;585 km to 4;878 km with a mean depth of 3;415 km; This result, therefore, indicates that the average basement depth of the study area obtained from the spectral analysis is 3;415km; This investigation, therefore provides appropriate sedimentary thickness for suitable hydrocarbon prospecting within the study area.

Abstract GNSS observations are usually used in periodic deformation monitoring. The Opak fault, which was in the Special Region of Yogyakarta, became a concern after the 2006 earthquake. The horizontal velocity values of each observation station are needed to estimate the slip rate and locking depth values of the Opak fault. The magnitude of the velocity vector is computed by the linear least square method, then translated into the Sunda Block reference frame. The creep of fault assumption is used in analyzing the potential for the earthquake in the Opak fault region. The velocity is done by reducing the Sunda Block using the Euler pole method, and it produces a velocity vector value on the east component is -6.08 to 5.25 mm/year while the north component is -3.38 to 5.74 mm/year. Meanwhile, in the northern segment of the Opak fault, the estimated slip rate is around 3.5 to 10.5 mm/year, with the locking depth obtained of 1.1 to 8 km, while in the southern segment of the Opak fault, the estimated slip rate is 4 to 5.5 mm/year, with a locking depth obtained of 0.6 to 1.2 km. The creep of the fault effect is predominantly in the southern segment of the Opak fault. This case indicates that the potential for earthquake hazards is smaller in the south segment than in the north segment.

A calculation method for obtaining the misorientation distribution function (MDF) for cubic crystals which can be used to estimate the presence or absence of special boundaries in the materials is presented. The calculation was carried out for two samples of Al-Mg-Si alloy subjected to various mechanical and thermal treatments: the first sample is subjected to rolling; the second sample is subjected to recrystallization annealing. MDF is calculated for each sample; the results are presented in the Euler space and in the angle-axis space. The novelty of the method consists in the possibility of gaining data on the grain boundaries from X-ray texture analysis without using electron microscopy. A calculation involving only mathematical operations on matrices was performed on the basis of the orientation distribution function restored from incomplete pole figures. It is shown that no special boundaries are observed in the deformed sample, whereas in the recrystallized alloy, special boundaries are detected at Ʃ = 23, 13, and 17. The shortcoming of the proposed method can be attributed to the lack of accurate data on grain boundaries, since all possible orientation in the polycrystal should be taken into account in MDF calculation.

This study utilized the interpretation of the airborne magnetic and radiometric data to delineate the potential structures that are associated with gold mineralization of the Minna and its environs, Northcentral Nigeria. The total field anomaly data was reduced to pole and upward continued in a bid to well positioned and enhanced the shallow (high pass) magnetic structures. The high pass structural lineaments were extracted and the resulting prominent E-W and NE-SW tectonic trends were revealed which are perhaps related to Eburnean (D1) and Pan-African (D2) deformation events respectively. Subsequently, numerous regions with relatively high degree of faulting and shearing effects were unraveled from the line density analysis of the high pass lineaments. The 3-D Euler deconvolution technique provides a synonymous trend pattern with the HP lineaments as well as estimate the depth extents to the potential structures with values varying between 82.7 and 211.9 m. It was found that the mineralized structures associated with gold over the study area interact with the hydrothermal fluids alongside/adjacent to the structurally deformed (relatively high degree of faulting and shearing effects) regions. The observed regions with coincident, of the hydrothermally altered and structurally deformed are therefore marked as the resourceful, structures for gold mineralization. Hence, the derived evidence from this study has updated the information on the structures that are associated with gold mineralization and also acts a mitigation major against the indiscriminate excavations of the studied region.

We show that potential fields enjoy valuable properties when they are scaled by specific power laws of the altitude. We describe the theory for the gravity field, the magnetic field, and their derivatives of any order and propose a method, called here Depth from Extreme Points (DEXP), to interpret any potential field. The DEXP method allows estimates of source depths, density, and structural index from the extreme points of a 3D field scaled according to specific power laws of the altitude. Depths to sources are obtained from the position of the extreme points of the scaled field, and the excess mass (or dipole moment) is obtained from the scaled field values. Although the scaling laws are theoretically derived for sources such as poles, dipoles, lines of poles, and lines of dipoles, we give also criteria to estimate the correct scaling law directly from the data. The scaling exponent of such laws is shown to be related to the structural index involved in Euler Deconvolution theory. The method is fast and stable because it takes advantage of the regular behavior of potential field data versus the altitude [Formula: see text]. As a result of stability, the DEXP method may be applied to anomalies with rather low SNRs. Also stable are DEXP applications to vertical and horizontal derivatives of a Newtonian potential of various orders in which we use theoretically determined scaling functions for each order of a derivative. This helps to reduce mutual interference effects and to obtain meaningful representations of the distribution of sources versus depth, with no prefiltering. The DEXP method does not require that magnetic anomalies to be reduced to the pole, and meaningful results are obtained by processing its analytical signal. Application to different cases of either synthetic or real data shows its applicability to any type of potential field investigation, including geological, petroleum, mining, archeological, and environmental studies.

The paper presents an improved algorithm based on Bhaskara Rao and Ramesh Babu’s algorithm to invert magnetic anomalies of three-dimensional basement structures. The magnetic basement is approximated by an ensemble of juxtaposed vertical prisms whose bottom surface coincides with Curie surface with the known depth. The computer program operating with the proposed algorithm is built in Matlab environment. Test applications show that the proposed method can perform computations with fast and stable convergence rate where the results also coincide well with the actual model structure. The effectiveness of the method is demonstrated by inverting magnetic anomalies of the southeast part of Vietnam continental shelf. The calculated magnetic basement relief of the study area provides useful additional information for studies in the aim of dealing with the geological structure of the area.References Beiki M., 2010. Analytic signals of gravity gradient tensor and their application to estimate source location, Geophysics, 75(6), i59–i74.Bui C.Q. (chief author), Le T., Tran T. D., Nguyen T. H., Phi T.T., 2007. Map of deep structure of the Earth’s crust, Atlas of the characteristics of natural conditions and environment in Vietnam’s waters and adjacent region. Publisher of Science and Technology, Ha Noi. Do D.T., Nguyen T.T.H., 2011. Atempt the improvement of inversion of magnetic anomalies of two dimensional polygonal cross sections to determine the depth of magnetic basement in some data profile of middle off shelf of Vietnam. Journal of Science and Technology, Vietnam Academy of Science and Technology, 49(2), 125–132.Do D.T., 2013. Study for application of 3D magnetic and gravity method to determine density contribution of basement rock and depth of magnetic basement on Vietnam’s shelf for oil research and prospecting Vietnam National University, Hanoi, Project code QG-11-04. Keating P. and Pilkington M., 2000, Euler deconvolution of the analytic signal, 62nd Annual International Meeting, EAGE, Session P0193.Keating P., Zerbo L., 1996. An improved technique for reduction to the pole at low latitudes, Geophysics, 61, 131–137.Le H.M., Luu V.H., 2003. Preliminary interpretation of the magnetic anomalies of the Eastern Vietnam sea and adiacent regions. J. Sci. of the Earth, 25(2), 173–181. Mai T.T., Pham V.T., Dang V.B., Le D.B., Nguyen B., Le V.D., 2011. Characteristics of Pliocene - Quaternary geology and Geoengineering in the Center and Southeast parts of Continental Shelf of Vietnam. J. Sci. of the Earth, 33(2), 109-118.Mushayandebvu M.F., Lesur V., Reid A.B., Fairhead J.D., 2004. Grid Euler deconvolution with constraints for 2D structures, Geophysics, 69, 489–496.Nguyen N.T., Bui V.N., Nguyen T.T.H., Than D.L., 2014a. Application of power density spectrum of magnetic anomaly to estimate the structure of magnetic layer of the earth crust in the Bac Bo gulf. Journal of Marine Science and Technology, 14(4A), 137–148.Nguyen N.T., Bui V.N., Nguyen T.T.H., 2014b. Determining the depth to the magnetic basementand fault systems in Tu Chinh - Vung May area by magnetic data interpretation. Journal of Marine Science and Technology, 14(4A), 16–25.Nguyen T.T.H., Pham T.L., Do D.T., Le H.M., 2018. Improving algorithm of determining the coordinates of the vertices of the polygon to invert magnetic anomalies of two-dimensional basement structures in space domain, Journal of Marine Science and Technology (preparing to print).Parker R.L., 1973. The rapid calculation of potential anomalies, Geophys. J. Roy. Astron. Soc, 31, 447–455. Pilkington M., Gregotski M.E., Todoeschuck J.P., 1994. Using fractal crustal magnetization models in magnetic interpretation, Geophysical Prospecting, 42, 677–692.Pilkington M., 2006. Joint inversion of gravity and magnetic data for two-layer models, Geophysics, 71, L35–L42.Rao D.B., Babu N.R., 1993. A fortran 77 computer program for three dimensional inversion of magnetic anomalies resulting from multiple prismatic bodies, Computer & Geosciences, 19(8), 781–801.Tanaka A., Okubo Y., Matsubayashi O., 1999. Curie point depth based on spectrum analysis of the magnetic anomaly data in East and Southeast Asia, Tectonic Pphysics, 306, 461–470.Thompson D.T., 1982. EULDTH – A new technique for marking computer-assisted depth estimates from magnetic data, Geophysics, 47, 31–37.Vo T.S., Le H.M., Luu V.H., 2005. Determining the horizontal position and depth of the density discontinuties in Red River Delta by using the vertical derivative and Euler deconvolution for the gravity anomaly data, Vietnam. Journal of Geology, Series A, 287(3–4), 39–52. Werner S., 1955. Interpretation of magnetic anomalies of sheet-like bodies, Sveriges Geologiska Undersokning, Series C, Arsbok, 43, 6.Xu S.Z., 2006. The integral-iteration method for continuation of potential fields, Chinese journal of geophysics (in Chinese), 49(4), 1176–1182.Zhang C., Huang D.N., Zhang K., Pu Y.T., Yu P., 2016. Magnetic interface forward and inversion method based on Padé approximation, Applied Geophysics, 13(4), 712–720.CCOP, 1996. Magnetic anomaly map of East Asia, scale 1:4.000.000, Geological survey of Japan and Committee for co-ordination of joint prospecting for mineral resources in asian offshore areas.

We present the estimated horizontal velocities of different lithotectonic segments of the NW Himalaya using data recorded by the eighteen GPS observatories installed in the Jammu and Kashmir region. The data was acquired from 2016 to 2019 and was processed using high precision GAMIT/GLOBK software. With respect to ITRF08 reference frame, the site motion in the region varies from 35 mm/yr to 45 mm/yr towards north-east. The India fixed site motion was estimated using the Ader's Euler pole of rotation. This yielded site motion varying from 2.4 to 11 mm/yr towards south-west and is consistent with the reported plate motion in the Northwest Himalaya. Further study with additional GPS networks is expected to provide precise estimates of deformation in the locked and creeping zones of the main Himalayan thrust in the Northwest Himalaya.

AbstractGNSS-based velocity fields are a key tool to assess the boundaries around major deforming areas, to explain the main patterns of surface motion and deformation, to analytically review existing kinematics models and finally, to study the underlying tectonic activities. Determination of a velocity field for Africa is of great importance in the determination of the African Reference Frame; this is essential for better understanding the African plate tectonics. Therefore, this study focusses on the determination of the African velocity fields using continuously operated GNSS stations. We processed and analyzed 11 years of data obtained from a total number of 145 GNSS site using GFZ’s EPOS.P8 software. The result shows that Africa moves in the North-East direction. The station coordinates derived with PPP show averaged RMS values of 2.9 mm, 9.9 mm and 8.5 mm for the north, east and up components with respect to the estimated trajectory models. Horizontal velocities at sites located on stable Nubia plate fit a single plate model with residual motion below 1 mm/year of RMS. We confirm significant southeast motion in Morocco and Zambia with residual velocities of 1.4 mm/year and 0.9 mm/year, respectively. We estimate the Euler Poles for Nubia and Somalia with 48.59°N, −78.64°E, 0.264°/Myr and 60.38°N, −83.33°E, 0.272°/Myr, respectively. Vertical velocities range from −2 to +2 mm/year, close to their uncertainties, with no distinct geographic pattern. The study also provides continental-wide position and velocity field solution for Africa, and can also be considered as a contribution to the upcoming AFREF, the African Geodetic Reference Frame.

The Asteroid Impact and Deflection Assessment (AIDA) is an international collaboration between the European Space Agency (ESA) and the National Aeronautics and Space Administration (NASA) aiming to investigate the binary asteroid system‎(65803) Didymos and to demonstrate asteroid deflection technique with kinetic impact. NASA’s Double Asteroid Redirection Test (DART) mission successfully impacted Dimorphos, the moon of the binary system, in September 2022. ESA’s contribution is the Hera mission that will rendezvous with Didymos and observe the impact effects closely. The Close Observation Phase (COP) is the proximity operation of Hera mission with the objective of obtaining high-resolution images of Dimorphos and fully characterizing the impact crater. Autonomous optical navigation system is designed for this phase based on line-of-sight and range measurements from both the primary body and Dimorphos in order to estimate the relative position of the spacecraft. The close distance between the primary and the spacecraft during the COP allows the implementation of feature tracking relative navigation to solve the primary’s relative attitude. Nevertheless, the relative attitude of Dimorphos remains unsolved as it requires closer distance. This paper develops an innovative methodology to estimate the continuous six degree of freedom pose (position and attitude) of Dimorphos during the COP using a Convolutional Neural Networks (CNN)-based Image Processing (IP) algorithm. For the attitude, we implement an appearance-based method that consists of two stages. In the first stage, we use CNNs with the images captured by the spacecraft on-board camera to regress a set of keypoints segmenting Dimorphos from its background. In the second stage, we use Neural Networks (NN) to map these keypoints to the three Euler angles representing the relative rotation matrix of Dimorphos with respect to the spacecraft. The estimated keypoints are also used to estimate the position of the centroid of Dimorphos and its relative distance with respect to the spacecraft, which together provides the relative position vector of the spacecraft. For the distance, the shape of Dimorphos is approximated to an ellipse of size and shape depending on its relative attitude with respect to the spacecraft. The regressed keypoints are used to evaluate the apparent semi-minor and semi-major axes of Dimorphos, which are used to estimate the range from the spacecraft using the pinhole camera model. The High-Resolution Network (HRNet) is used as CNN architecture as it represents the state-of-the-art technology in keypoint detection with its capability of maintaining high resolution representations of the input images by connecting multiple subnetworks in parallel. For attitude navigation, the appearance-based method is selected for three main reasons. Firstly, it has the main advantage of a reduced dependency on the distance that is the main driver for a feature tracking relative navigation technique. Secondly, other methods such as model-based ones require sufficiently regular shapes of the targets, which is not the case of near-earth objects such as asteroids. Thirdly, the appearance-based method does not depend on prior knowledge of spinning axis and rate of the target, which appears to be chaotic for Dimorphos after the impact with DART. The training, validation and testing datasets consist of synthetic images generated with the software Planet and Asteroid Natural scene Generation Utility (PANGU) at different epochs of the COP trajectory provided by ESA. Additional images generated from different trajectory segments around the binary system are used to augment the training database. Therefore, our develop algorithm is expected to solve the overall pose estimation and improve the efficiency and the robustness of the autonomous navigation of the proximity operations of Hera mission.

Offshore structures are founded on submerged foundations. The excavation of submerged foundations in the sea bed is a difficult task to accomplish when it comes to the decommissioning of these offshore structures. The extraction resistance is a lot higher than the pressure acting on the structure due to hydrostatic pressure, earth pressure and its self-weight. Once the extraction begins, a negative pore water pressure is created until inflowing pore water compensates this negative pore water pressure. This depression is hindering the extraction of the submerged foundation. Additionally, the resistance is dependent on the embedment depth of the structure, the soil properties as well as the extraction velocity, which influences the dimension of the negative pore water pressure. The numerical investigation of this dynamic problem is a limitation for continuum based approaches like the Finite Element Method (FEM) due to the occurring large deformations. These results from the soil bed failing under the movement of the structure and hence starting to flow. Additionally, in order to estimate the created depression, the investigation of the water-soil-interaction is crucial, as the change of the pore water pressure plays a significant role. Therefore, it is necessary to analyze the behavior of the soil particles and the pore water pressure. In order to do this, a coupled Euler-Lagrange approach, namely the combination of Computational Fluid Dynamics (CFD) and the Discrete Element Method (DEM), is used. In these simulations on one hand, the liquid phase, e.g. the water, is considered as a continuum, while on the other hand, for the solid phase, e.g. the soil, a particle representation is chosen. Hence, it is possible to compute the particle-particle — as well as the fluid-particle-interactions. The calculations are carried out with the open source software package CFDEMcoupling®, which combines the discrete element code LIGGGHTS® with CFD solvers based on OpenFOAM®. This paper introduces the coupled CFD-DEM approach to simulate the extraction of a submerged plate in the soil bed. In this work, the soil grains are idealized by spherical particles of different diameters. In order to consider effects of dilatancy and contractancy in the soil bed, different relative densities are investigated. Additionally, a variation of the extraction velocity of the plate is carried out to examine the dependence on the creation of negative pore water pressure. For each case, the extraction resistance is calculated. The flow velocity and the pressure distribution in the vicinity of the structure are analyzed.