3D Stratigraphic Modeling of Central Aachen
NASA Astrophysics Data System (ADS)
Dong, M.; Neukum, C.; Azzam, R.; Hu, H.
2010-05-01
Since 1980s, advanced computer hardware and software technologies, as well as multidisciplinary research have provided possibilities to develop advanced three dimensional (3D) simulation software for geosciences application. Some countries, such as USA1) and Canada2) 3), have built up regional 3D geological models based on archival geological data. Such models have played huge roles in engineering geology2), hydrogeology2) 3), geothermal industry1) and so on. In cooperating with the Municipality of Aachen, the Department of Engineering Geology of RWTH Aachen University have built up a computer-based 3D stratigraphic model of 50 meter' depth for the center of Aachen, which is a 5 km by 7 km geologically complex area. The uncorrelated data from multi-resources, discontinuous nature and unconformable connection of the units are main challenges for geological modeling in this area. The reliability of 3D geological models largely depends on the quality and quantity of data. Existing 1D and 2D geological data were collected, including 1) approximately 6970 borehole data of different depth compiled in Microsoft Access database and MapInfo database; 2) a Digital Elevation Model (DEM); 3) geological cross sections; and 4) stratigraphic maps in 1m, 2m and 5m depth. Since acquired data are of variable origins, they were managed step by step. The main processes are described below: 1) Typing errors of borehole data were identified and the corrected data were exported to Variowin2.2 to distinguish duplicate points; 2) The surface elevation of borehole data was compared to the DEM, and differences larger than 3m were eliminated. Moreover, where elevation data missed, it was read from the DEM; 3) Considerable data were collected from municipal constructions, such as residential buildings, factories, and roads. Therefore, many boreholes are spatially clustered, and only one or two representative points were picked out in such areas; After above procedures, 5839 boreholes with -x
Stratigraphic and structural interpretation with 3-D coherence
Bahorich, M.S.; Lopez, J.; Haskell, N.L.
1995-12-31
3-D seismic coherence is useful for identifying faults, stratigraphic features and the relationship between them (Bahorich, and Farmer, 1994). This paper documents the use of this technology in three basins; the Gulf of Mexico, the North Sea, and the Ardmore Basin of Oklahoma.
Stratigraphic and structural interpretation with 3-D seismic coherence
Bahorich, M.; Lopez, J.; Haskell, N.
1996-12-31
3-D seismic discontinuity is useful for identifying faults, stratigraphic features and the relationship between them. This paper covers the application of coherence technology to three basins; the Gulf of Mexico, the North Sea, aid the Ardmore Basin of Oklahoma. In the Gulf of Mexico, 3-D coherence data may be used to simultaneously view faults and stratigraphic features and therefore see the relationship between them. Coherence data reveal channels that avoid a structural high generated by a salt dome, Channels that change direction as they cross faults, radial faults adjacent to a salt dome, and complex and en-echelon faults. Since the coherence process is applied to non- interpreted seismic data, these features are available for viewing without the time or bias of interpretation. Coherence time slices from the Ardmore Basin of Oklahoma were compared with a horizon-dip map and a discrepancy in the fault patterns was noted. Further analysis revealed that subtle errors in the autopicking had created a false bend in a fault trace seen on the horizon-dip map. After correction, the horizon-dip map and coherence time slice indicated similar fault patterns. Since the coherence method is run on the raw seismic data, it provides a view of the faults that is not biased by the interpreter or horizon autopicker. In the North Sea, faults may exhibit meandering patterns that are easy to interpret on traditional time-slices where they cut perpendicular to stratigraphic bedding but are difficult to recognize where they cut parallel to bedding. The coherence technique images faults in any orientation equally well.
Stratigraphic and structural interpretation with 3-D seismic coherence
Bahorich, M.; Lopez, J.; Haskell, N.; Nissen, S.; Poole, A.
1996-06-01
3-D seismic discontinuity is useful for identifying faults, stratigraphic features and the relationship between them. This paper covers the application of coherence technology to three basins; the Gulf of Mexico, the North Sea, and the Ardmore Basin of Oklahoma. In the Gulf of Mexico, 3-D coherence data may be used to simultaneously view faults and stratigraphic features and therefore see the relationship between them. Coherence data reveal channels that avoid a structural high generated by a salt dome, channels that change direction as they cross faults, radial faults adjacent to a salt dome, and complex and en-echelon faults. Since the coherence process is applied to non-interpreted seismic data, these features are available for viewing without the time or bias of interpretation. Coherence time slices from the Ardmore Basin of Oklahoma were compared with a horizon-dip map and a discrepancy in the fault patterns was noted. Further analysis revealed that subtle errors in the autopicking had created a false bend in a fault trace seen on the horizon-dip map. After correction, the horizon-dip map and coherence time slice indicated similar fault patterns. Since the coherence method is run on the raw seismic data, it provides a view of the faults that is not biased by the interpreter or horizon autopicker. In the North Sea, faults may exhibit meandering patterns that are easy to interpret on traditional time-slices where they cut perpendicular to stratigraphic bedding but are difficult to recognize where they cut parallel to bedding. The coherence technique images faults in any orientation equally well.
3D Gravity Inversion using Tikhonov Regularization
NASA Astrophysics Data System (ADS)
Toushmalani, Reza; Saibi, Hakim
2015-08-01
Subsalt exploration for oil and gas is attractive in regions where 3D seismic depth-migration to recover the geometry of a salt base is difficult. Additional information to reduce the ambiguity in seismic images would be beneficial. Gravity data often serve these purposes in the petroleum industry. In this paper, the authors present an algorithm for a gravity inversion based on Tikhonov regularization and an automatically regularized solution process. They examined the 3D Euler deconvolution to extract the best anomaly source depth as a priori information to invert the gravity data and provided a synthetic example. Finally, they applied the gravity inversion to recently obtained gravity data from the Bandar Charak (Hormozgan, Iran) to identify its subsurface density structure. Their model showed the 3D shape of salt dome in this region.
Novel Scalable 3-D MT Inverse Solver
NASA Astrophysics Data System (ADS)
Kuvshinov, A. V.; Kruglyakov, M.; Geraskin, A.
2016-12-01
We present a new, robust and fast, three-dimensional (3-D) magnetotelluric (MT) inverse solver. As a forward modelling engine a highly-scalable solver extrEMe [1] is used. The (regularized) inversion is based on an iterative gradient-type optimization (quasi-Newton method) and exploits adjoint sources approach for fast calculation of the gradient of the misfit. The inverse solver is able to deal with highly detailed and contrasting models, allows for working (separately or jointly) with any type of MT (single-site and/or inter-site) responses, and supports massive parallelization. Different parallelization strategies implemented in the code allow for optimal usage of available computational resources for a given problem set up. To parameterize an inverse domain a mask approach is implemented, which means that one can merge any subset of forward modelling cells in order to account for (usually) irregular distribution of observation sites. We report results of 3-D numerical experiments aimed at analysing the robustness, performance and scalability of the code. In particular, our computational experiments carried out at different platforms ranging from modern laptops to high-performance clusters demonstrate practically linear scalability of the code up to thousands of nodes. 1. Kruglyakov, M., A. Geraskin, A. Kuvshinov, 2016. Novel accurate and scalable 3-D MT forward solver based on a contracting integral equation method, Computers and Geosciences, in press.
3D Electromagnetic inversion using conjugate gradients
Newman, G.A.; Alumbaugh, D.L.
1997-06-01
In large scale 3D EM inverse problems it may not be possible to directly invert a full least-squares system matrix involving model sensitivity elements. Thus iterative methods must be employed. For the inverse problem, we favor either a linear or non-linear (NL) CG scheme, depending on the application. In a NL CG scheme, the gradient of the objective function is required at each relaxation step along with a univariate line search needed to determine the optimum model update. Solution examples based on both approaches will be presented.
3-D Numerical Stratigraphic Forward Modeling of Rifts
NASA Astrophysics Data System (ADS)
Lovely, P. J.; Harris, A.; Baumgardner, S. E.; Engelder, T.; Sun, T.; Lyons, R. P.; Granjeon, D.
2016-12-01
Continental rifts are of great interest and relevance to scientists and the general public because they contain numerous depositional environments at relatively compressed spatiotemporal scales, continuous climate records, and hydrocarbon resources. The interaction of climate, sediment routing, and tectonism controls the distribution and continuity of the depositional environments, but these relationships are nonlinear and complex. Conceptual stratigraphic models provide useful insight into facies distribution but are typically qualitative and may not capture the full range of geologically plausible scenarios generated by these interactions. Here, we use a numerical forward stratigraphic model to demonstrate that a deterministic, nonlinear diffusion-based sediment transport model can approximate key tectonostratigraphic processes interpreted from continental rift systems. The sediment transport model acts upon a simple elastic tectonic model that approximates appropriate distributions of subsidence and uplift associated with a schematic fault architecture typical of early stage continental rifting. Comparison of model results to observations of outcrops and the subsurface demonstrates the model's ability to reproduce key tectonostratigraphic features. We also show that such a model may be used to analyze the sensitivity of sand distributions to base-level, sediment, and water flux changes. We present an example analysis with a suite of metrics such as sand thickness, net-to-gross, and mass extraction methods that quantitatively describe the deposits that result from various inputs. This simple sensitivity analysis can be conducted by academic and industry groups to better characterize facies distribution or quantify uncertainties associated with continental rifts.
3-D radial gravity gradient inversion
NASA Astrophysics Data System (ADS)
Oliveira, Vanderlei C.; Barbosa, Valéria C. F.
2013-11-01
We have presented a joint inversion of all gravity-gradient tensor components to estimate the shape of an isolated 3-D geological body located in subsurface. The method assumes the knowledge about the depth to the top and density contrast of the source. The geological body is approximated by an interpretation model formed by an ensemble of vertically juxtaposed 3-D right prisms, each one with known thickness and density contrast. All prisms forming the interpretation model have a polygonal horizontal cross-section that approximates a depth slice of the body. Each polygon defining a horizontal cross-section has the same fixed number of vertices, which are equally spaced from 0° to 360° and have their horizontal locations described in polar coordinates referred to an arbitrary origin inside the polygon. Although the number of vertices forming each polygon is known, the horizontal coordinates of these vertices are unknown. To retrieve a set of juxtaposed depth slices of the body, and consequently, its shape, our method estimates the radii of all vertices and the horizontal Cartesian coordinates of all arbitrary origins defining the geometry of all polygons describing the horizontal cross-sections of the prisms forming the interpretation model. To obtain a stable estimate that fits the observed data, we impose constraints on the shape of the estimated body. These constraints are imposed through the well-known zeroth- and first-order Tikhonov regularizations allowing, for example, the estimate of vertical or dipping bodies. If the data do not have enough in-depth resolution, the proposed inverse method can obtain a set of stable estimates fitting the observed data with different maximum depths. To analyse the data resolution and deal with this possible ambiguity, we plot the ℓ2-norm of the residuals (s) against the estimated volume (vp) produced by a set of estimated sources having different maximum depths. If this s × vp curve (s as a function of vp) shows a well
Kerr, J. ); Jones, G.L. )
1996-01-01
Recent advances in hardware and software have given the interpreter and engineer new ways to view 3D seismic data and well bore information. Recent papers have also highlighted the use of various statistics and seismic attributes. By combining new 3D rendering technologies with recent trends in seismic analysis, the interpreter can improve the structural and stratigraphic resolution of hydrocarbon reservoirs. This paper gives several examples using 3D visualization to better define both the structural and stratigraphic aspects of several different structural types from around the world. Statistics, 3D visualization techniques and rapid animation are used to show complex faulting and detailed channel systems. These systems would be difficult to map using either 2D or 3D data with conventional interpretation techniques.
Kerr, J.; Jones, G.L.
1996-12-31
Recent advances in hardware and software have given the interpreter and engineer new ways to view 3D seismic data and well bore information. Recent papers have also highlighted the use of various statistics and seismic attributes. By combining new 3D rendering technologies with recent trends in seismic analysis, the interpreter can improve the structural and stratigraphic resolution of hydrocarbon reservoirs. This paper gives several examples using 3D visualization to better define both the structural and stratigraphic aspects of several different structural types from around the world. Statistics, 3D visualization techniques and rapid animation are used to show complex faulting and detailed channel systems. These systems would be difficult to map using either 2D or 3D data with conventional interpretation techniques.
Fajardo, A.A. ); Cross, T.A. )
1996-01-01
A high-resolution sequence stratigraphic study using 2300 feet of core calibrated with geophysical logs from 14 wells and 1800 measurements of porosity and permeability established the 4-D stratigraphy and 3-D reservoir zonation of the Mirador. Virtually all reservoir-quality facies are through cross-stratified sandstones which occur in channel facies successions in the lower Mirador, but in bay-head delta and estuarine channel facies successions in the upper Mirador. Petrophysical properties and the geometry, continuity and volume of reservoir-quality sandstones change regularly as function of their stratigraphic position. These vertical facies successions reflect increasing accommodation-to-sediment supply (A/S) ratio through each intermediate-term cycle. The upper long-term cycle comprises four intermediate-term, landward-stepping, symmetrical base-level cycles. These cycles consist of estuarine channel, bay-head to bay-fill facies successions. The transition from channel to bay-head to bay-fill facies successions represents an increase in A/S ratio, and the reverse transition indicates a decrease in A/S ratio. Sixteen reservoir zones were defined within the Cusiana field. Reservoirs within the upper and lower long-term cycles are separated by a continuous middle Mirador mudstone which creates two large reservoir divisions. At the second level of zonation, the reservoir compartments and fluid-flow retardants coincide with the intermediate-term stratigraphic cycles. A third level of reservoir compartmentalization follows the distribution of facies successions within the intermediate-term cycles. A strong stratigraphic control on reservoir properties occurs at the three scales of stratigraphic cyclicity. In all cases as A/S ratio increases, porosity and permeability decrease.
Fajardo, A.A.; Cross, T.A.
1996-12-31
A high-resolution sequence stratigraphic study using 2300 feet of core calibrated with geophysical logs from 14 wells and 1800 measurements of porosity and permeability established the 4-D stratigraphy and 3-D reservoir zonation of the Mirador. Virtually all reservoir-quality facies are through cross-stratified sandstones which occur in channel facies successions in the lower Mirador, but in bay-head delta and estuarine channel facies successions in the upper Mirador. Petrophysical properties and the geometry, continuity and volume of reservoir-quality sandstones change regularly as function of their stratigraphic position. These vertical facies successions reflect increasing accommodation-to-sediment supply (A/S) ratio through each intermediate-term cycle. The upper long-term cycle comprises four intermediate-term, landward-stepping, symmetrical base-level cycles. These cycles consist of estuarine channel, bay-head to bay-fill facies successions. The transition from channel to bay-head to bay-fill facies successions represents an increase in A/S ratio, and the reverse transition indicates a decrease in A/S ratio. Sixteen reservoir zones were defined within the Cusiana field. Reservoirs within the upper and lower long-term cycles are separated by a continuous middle Mirador mudstone which creates two large reservoir divisions. At the second level of zonation, the reservoir compartments and fluid-flow retardants coincide with the intermediate-term stratigraphic cycles. A third level of reservoir compartmentalization follows the distribution of facies successions within the intermediate-term cycles. A strong stratigraphic control on reservoir properties occurs at the three scales of stratigraphic cyclicity. In all cases as A/S ratio increases, porosity and permeability decrease.
Joint inversions of two VTEM surveys using quasi-3D TDEM and 3D magnetic inversion algorithms
NASA Astrophysics Data System (ADS)
Kaminski, Vlad; Di Massa, Domenico; Viezzoli, Andrea
2016-05-01
In the current paper, we present results of a joint quasi-three-dimensional (quasi-3D) inversion of two versatile time domain electromagnetic (VTEM) datasets, as well as a joint 3D inversion of associated aeromagnetic datasets, from two surveys flown six years apart from one another (2007 and 2013) over a volcanogenic massive sulphide gold (VMS-Au) prospect in northern Ontario, Canada. The time domain electromagnetic (TDEM) data were inverted jointly using the spatially constrained inversion (SCI) approach. In order to increase the coherency in the model space, a calibration parameter was added. This was followed by a joint inversion of the total magnetic intensity (TMI) data extracted from the two surveys. The results of the inversions have been studied and matched with the known geology, adding some new valuable information to the ongoing mineral exploration initiative.
Full 3-D inversion of electromagnetic data on PC
NASA Astrophysics Data System (ADS)
Sasaki, Yutaka
2001-01-01
Three-dimensional (3-D) electromagnetic (EM) inversion might be believed to require high-performance computers. However, with the rapid progress of recent computer technology, running 3-D inversions on personal computers (PC) is becoming a rational choice. This paper describes an attempt to carry out full 3-D inversions of synthetic frequency-domain EM data on a PC. In the inversion, a staggered-grid finite difference scheme is used to solve for the secondary electric field. The system of equations is solved using the incomplete Cholesky biconjugate gradient (ICBCG) method. By applying the static divergence correction proposed by Smith [Geophysics 61 (1996) 1319-1324], the rates of convergence are dramatically improved, and the forward calculation per source location on a medium-size grid takes only a few minutes on a PC. The sensitivities of the EM responses to subsurface resistivity changes are calculated from forward solutions using the reciprocity relation. An inverse problem is formulated so that a model is found that has a smooth structure and at the same time is close to an initial model, and is solved with an iterative least-squares method. A synthetic example for an airborne EM survey shows that the lateral extents of 3-D bodies are well resolved, and the vertical coil coaxial system gives a better lateral resolution than the horizontal coil coplanar system. An example for a ground EM survey shows that expanding the survey coverage or aperture is needed to improve the resolution at depth.
3D semiconducting nanostructures via inverse lipid cubic phases.
Burton, M R; Lei, C; Staniec, P A; Terrill, N J; Squires, A M; White, N M; Nandhakumar, Iris S
2017-07-25
Well-ordered and highly interconnected 3D semiconducting nanostructures of bismuth sulphide were prepared from inverse cubic lipid mesophases. This route offers significant advantages in terms of mild conditions, ease of use and electrode architecture over other routes to nanomaterials synthesis for device applications. The resulting 3D bicontinous nanowire network films exhibited a single diamond topology of symmetry Fd3m (Q227) which was verified by Small angle X-ray scattering (SAXS) and Transmission electron microscopy (TEM) and holds great promise for potential applications in optoelectronics, photovoltaics and thermoelectrics.
3D Magnetic inversion and remanence: solving the problem
NASA Astrophysics Data System (ADS)
Thomson, V.; Morris, W.
2003-04-01
3D inversion of surface magnetic data is a common processing technique when used in mineral exploration. The major drawback of most 3D inversion algorithms is that they assume that the surface magnetic anomaly is produced by induced magnetization and that there are no remanent magnetization or demagnetization effects present. This has a significant impact when modeling magnetic data that has remanent magnetization. The magnetic anomaly produced by a dipping subsurface body will be identical for a consistent relationship between the dip of the body and the dip of the magnetic vector, regardless of the actual dip of the magnetic body. For example, in the case where a subsurface body is dipping, such as a dipping dike, the dip estimated by the inversion routine will be correct only if induced magnetization is present. This has serious implications for mineral exploration. A solution to the remanence problem is to model the surface magnetic anomaly using a constrained 2D approach rather than 3D. Using a priori information on dip and strike length of a source body, it is possible to approximate the remanence direction and intensity. The 2D solutions can then be rendered into a 3D imaging package to create a model in 3D. A case study was performed on a mafic-ultramafic layered igneous intrusion located in Big Trout Lake, northwestern Ontario, Canada. Large layered igneous intrusions are known to have significant remanence. Like many other layered igneous intrusions such as the Bushveld Complex in South Africa, the Big Trout Lake Complex is highly prospective for Platinum Group Elements (PGEs). Intruded during Archean time, the Big Trout Lake Complex has been subsequently folded and faulted to near vertical. As a consequence of limited surface exposures, knowledge of layering within the pluton and the extent of deformation of the pluton is very limited. Newly acquired high-resolution aeromagnetic data shows a strongly mineralized horizon within the intrusion that
Image Appraisal for 2D and 3D Electromagnetic Inversion
Alumbaugh, D.L.; Newman, G.A.
1999-01-28
Linearized methods are presented for appraising image resolution and parameter accuracy in images generated with two and three dimensional non-linear electromagnetic inversion schemes. When direct matrix inversion is employed, the model resolution and posterior model covariance matrices can be directly calculated. A method to examine how the horizontal and vertical resolution varies spatially within the electromagnetic property image is developed by examining the columns of the model resolution matrix. Plotting the square root of the diagonal of the model covariance matrix yields an estimate of how errors in the inversion process such as data noise and incorrect a priori assumptions about the imaged model map into parameter error. This type of image is shown to be useful in analyzing spatial variations in the image sensitivity to the data. A method is analyzed for statistically estimating the model covariance matrix when the conjugate gradient method is employed rather than a direct inversion technique (for example in 3D inversion). A method for calculating individual columns of the model resolution matrix using the conjugate gradient method is also developed. Examples of the image analysis techniques are provided on 2D and 3D synthetic cross well EM data sets, as well as a field data set collected at the Lost Hills Oil Field in Central California.
EMSchur3D: Airborne EM inversion using decoupled potentials
NASA Astrophysics Data System (ADS)
Irons, T. P.
2015-12-01
Airborne electromagnetics (AEM) investigations have established themselves as an invaluable tool for near-surface investigation. They are an economical and efficient means to rapidly obtain a geophysical characterization of electrical properties of the subsurface, which can often be correlated with lithology as well as water content and quality. While many AEM surveys are inherently aimed at obtaining a 3D image of the earth, the most mature means of data interpretation involves stitched 1D inversions. In many AEM surveys the geology is generally layered and changes slowly enough along the survey such that the earth beneath the instrument at any moment is effectively 1D-justifying this approach. However, AEM surveys are being conducted in increasingly challenging locales where these assumptions break down. AEM surveys in areas with large topographic relief, complicated geology, and/or surveys that are concentrated on characterizing compact features do not permit a 1D approximation. The 3D inverse problem is computationally challenging due to large memory requirements as well as the singular nature of Maxwell's equations in the air. We propose a deterministic 3D inversion methodology utilizing a vector- and scalar-potential frequency-domain formulation of Maxwell's equations, which is not degenerate in the air. The potentials are decoupled through Schur decomposition resulting in smaller systems in the forward-problem formulation and no redundant matrix storage. The Schur decomposition also permits the reuse of direct solvers within the forward problem. Time-domain calculations are made tractable by avoiding costly solver refactoring at every frequency and conductivity model. The computational mesh is necessarily finer than the resolving power of the survey and reduced order models are relied upon in order to avoid nearly redundant sensitivity calculations. The proposed inversion approach is able to reproduce 3D features and avoids biases and inaccuracies of 1D
The novel high-performance 3-D MT inverse solver
NASA Astrophysics Data System (ADS)
Kruglyakov, Mikhail; Geraskin, Alexey; Kuvshinov, Alexey
2016-04-01
We present novel, robust, scalable, and fast 3-D magnetotelluric (MT) inverse solver. The solver is written in multi-language paradigm to make it as efficient, readable and maintainable as possible. Separation of concerns and single responsibility concepts go through implementation of the solver. As a forward modelling engine a modern scalable solver extrEMe, based on contracting integral equation approach, is used. Iterative gradient-type (quasi-Newton) optimization scheme is invoked to search for (regularized) inverse problem solution, and adjoint source approach is used to calculate efficiently the gradient of the misfit. The inverse solver is able to deal with highly detailed and contrasting models, allows for working (separately or jointly) with any type of MT responses, and supports massive parallelization. Moreover, different parallelization strategies implemented in the code allow optimal usage of available computational resources for a given problem statement. To parameterize an inverse domain the so-called mask parameterization is implemented, which means that one can merge any subset of forward modelling cells in order to account for (usually) irregular distribution of observation sites. We report results of 3-D numerical experiments aimed at analysing the robustness, performance and scalability of the code. In particular, our computational experiments carried out at different platforms ranging from modern laptops to HPC Piz Daint (6th supercomputer in the world) demonstrate practically linear scalability of the code up to thousands of nodes.
Petroleum Systems of South Kara Basin: 3D stratigraphic simulation and basin modeling results
NASA Astrophysics Data System (ADS)
Malysheva, S.; Vasilyev, V.; Verzhbitsky, V.; Ananyev, V.; Murzin, R.; Komissarov, D.; Kosenkova, N.; Roslov, Yu.
2012-04-01
Petroleum systems of South Kara Basin are still poorly studied and hydrocarbon resource estimates vary depending on geological models and understanding of the basin evolution. The main purpose of the regional studies of South Kara Basin was to produce a consistent model, which would be able to explain the existence of the fields discovered in the area as well as to determine the most favorable hydrocarbon accumulation zones in the study area for further exploration. In the study 3D stratigraphic simulation and basin modeling of South Kara Basin was carried out. The stratigraphic simulation results, along with geological, geophysical and geochemical data for the inland areas of Yamal and Gydan peninsulas and South Kara islands enabled to predict the lithological composition and distribution of source rocks, reservoirs and seals in the Kara Sea offshore area. Based on the basin modeling results hydrocarbon accumulations may occur in the reservoir facies of the wide stratigraphic range from Jurrasic to Cretaceous. The main source for the hydrocarbons, accumulated in the South Kara Basin Neocomian and Cenomanian reservoirs are the J3-K1 (the northward extension of Bazhenov Formation and its analogs of West Siberia), as well as J1 and probably J2 shales with predominantly marine type of kerogen (type II). Thermal and burial history restorations show that Lower Cretaceous (Aptian-Albian) sediments enriched with terrigenous organic matter (kerogen of type III) and containing coaly layers could not produce the hydrocarbon volumes to fill the giant Rusanovskoye and Leningradskoye gas-condensate fields as the K1 source rocks are not mature enough. The modeling results, in particular, suggest that the geologic conditions in the South Kara Basin are favorable for further discoveries of giant fields. Although gas accumulations are predominating in the basin, oil-and-gascondensate fields (not a pure oil fields though) with sufficient part of liquid hydrocarbons might be present
3D and 4D GPR for Stratigraphic and Hydrologic Characterization of Field Sites
NASA Astrophysics Data System (ADS)
Grasmueck, M.; Viggiano, D. A.
2008-05-01
In a time of almost unlimited mobility, information, and connectivity it is surprising how our knowledge of natural systems becomes fragmented as soon as we enter the ground. Excavation, drilling, and 2D geophysics are unable to capture the spatio-temporal variability inside soil and rock volumes at the 1-10m scale. The problem is the lack of efficient and high-resolution imaging for the near surface domain. We have developed a high- resolution 3D Ground Penetrating Radar (GPR) system suitable for data acquisition at field sites. To achieve sharp and repeatable subsurface imaging we have integrated GPR with a rotary laser/IR strobe system. With 40 xyz coordinate updates per second, continuously moving GPR antennae can be tracked centimeter precise. A real-time LED guidance system shows the GPR antenna operator how to follow pre-computed survey tracks. Without having to stake out hundreds of survey tracks anymore one person now can scan an area of up to 600m2 per hour with a dual GPR antenna at 1m/s with 0.1m line spacing. The coordinate and GPR data are fused in real-time providing a first look of the subsurface in horizontal map view for quality control and in-field site assessment during data acquisition. The precision of the laser positioning system enables centimeter accurate repeat surveys to image and quantify water content changes in the vadose zone. To verify quantitative results of such 4D GPR we performed a controlled pond infiltration injecting 3200L of water from a 4x4m temporary pond with a thin soil layer and 5m of unsaturated porous limestone below. A total of sixteen repeated 3D GPR surveys were acquired just before the infiltration and in the following 2 weeks. All data were recorded with 250MHz antennae on a 5x10cm grid covering an area of 18x20m. Data processing included 3D migration and extraction of time shifts between pairs of time- lapse 3D GPR surveys. From the time shifts water content changes were computed using the Topp equation. The
3D-spectral CDIs: a fast alternative to 3D inversion?
NASA Astrophysics Data System (ADS)
Macnae, James
2015-09-01
Virtually all airborne electromagnetic (AEM) data is interpreted using stitched 1D conductivity sections, derived from constrained inversion or fast but fairly accurate approximations. A small subset of this AEM data recently has been inverted using either block 3D models or thin plates, which processes have limitations in terms of cost and accuracy, and the results are in general strongly biased by the choice of starting models. Recent developments in spectral modelling have allowed fast 3D approximations of the EM response of both vortex induction and current gathering for simple geological target geometries. Fitting these spectral responses to AEM data should be sufficient to accurately locate current systems within the ground, and the behaviour of these local current systems can in theory approximately define a conductivity structure in 3D. This paper describes the results of initial testing of the algorithm in fitting vortex induction in a small target at the Forrestania test range, Western Australia, using results from a versatile time-domain electromagnetic (VTEM)-Max survey.
A gravimetric 3D global inversion for cavity detection
Camacho, A.G.; Vieira, R.; Montesinos, F.G. . Faculty de CC. Matematicas); Cuellar, V. )
1994-02-01
A gravimetric survey, covering a site 200 m square, was carried out in order to locate karstic cavities. After eliminating the regional trend using a polynomial fit, the residual is modeled by least-squares prediction. Correlated signals for several wavelengths are detected. The inversion of these anomalies is performed by a global 3D adjustment using spherical bodies as models. The adjustment is repeated in order to obtain a stable configuration. The results show the probable presence of a system of cavities and galleries. Data collected from boreholes and the subsequent appearance of sink-holes are consistent with the results.
NASA Astrophysics Data System (ADS)
Goggin, L. R.
2014-12-01
Our understanding of subsurface stratigraphic relationships is guided by stratigraphic concepts that were developed using many varieties and scales of data including paleontological samples, cuttings and core, outcrop analogs, well logs, and seismic. Subsurface stratigraphic correlations are strongly influenced by the type, density, and distribution of the data available. The exploration geologist typically interprets 2D and 3D seismic reflections to define prospects and plays. In structurally simple areas, he or she often assumes that seismic reflectors mark depositional boundaries that are essentially time-synchronous events represented by a single wavelet character. In reality, seismic reflectors usually display spatial wavelet variability, seldom resolve individual beds and are the product of the amplitude expression of a range of lithologic changes that encompasses a range of geologic time and depositional processes. Our assumption that seismic reflections are time-synchronous can lead to errors in stratigraphic correlation that only become evident when our prediction of well or field performance is unrealized. To mitigate the potential for this correlation error, we must modify how we interpret seismic data. In this presentation we will focus on the concept of defining or approximating time-correlative surfaces in seismic data, leverage concepts of the Wheeler transform to place these seismic reflectors into the relative time domain and then examine the diachronous nature of these time-mapped surfaces in 3D. We will then explore how the 3D mapping of time-correlative surfaces fits sequence stratigraphic concepts and discuss whether this new approach requires us to change our interpretation paradigms.
3D electromagnetic inversion for environmental site characterization
Alumbaugh, D.L.; Newman, G.A.
1997-04-01
A 3-D non-linear electromagnetic inversion scheme has been developed to produce images of subsurface conductivity structure from electromagnetic geophysical data. The solution is obtained by successive linearized model updates where full forward modeling is employed at each iteration to compute model sensitivities and predicted data. Regularization is applied to the problem to provide stability. Because the inverse part of the problem requires the solution of 10`s to 100`s of thousands of unknowns, and because each inverse iteration requires many forward models to be computed, the code has been implemented on massively parallel computer platforms. The use of the inversion code to image environmental sites is demonstrated on a data set collected with the Apex Parametrics {open_quote}MaxMin I-8S{close_quote} over a section of stacked barrels and metal filled boxes at the Idaho National Laboratory`s {open_quote}Cold Test Pit{close_quote}. The MaxMin is a loop-loop frequency domain system which operates from 440 Hz up to 56 kHz using various coil separations; for this survey coil separations of 15, 30 and 60 feet were employed. The out-of phase data are shown to be of very good quality while the in-phase are rather noisy due to slight mispositioning errors, which cause improper cancellation of the primary free space field in the receiver. Weighting the data appropriately by the estimated noise and applying the inversion scheme is demonstrated to better define the structure of the pit. In addition, comparisons are given for single coil separations and multiple separations to show the benefits of using multiple offset data.
Computational and methodological developments towards 3D full waveform inversion
NASA Astrophysics Data System (ADS)
Etienne, V.; Virieux, J.; Hu, G.; Jia, Y.; Operto, S.
2010-12-01
Full waveform inversion (FWI) is one of the most promising techniques for seismic imaging. It relies on a formalism taking into account every piece of information contained in the seismic data as opposed to more classical techniques such as travel time tomography. As a result, FWI is a high resolution imaging process able to reach a spatial accuracy equal to half a wavelength. FWI is based on a local optimization scheme and therefore the main limitation concerns the starting model which has to be closed enough to the real one in order to converge to the global minimum. Another counterpart of FWI is the required computational resources when considering models and frequencies of interest. The task becomes even more tremendous when one tends to perform the inversion using the elastic equation instead of using the acoustic approximation. This is the reason why until recently most studies were limited to 2D cases. In the last few years, due to the increase of the available computational power, FWI has focused a lot of interests and continuous efforts towards inversion of 3D models, leading to remarkable applications up to the continental scale. We investigate the computational burden induced by FWI in 3D elastic media and propose some strategic features leading to the reduction of the numerical cost while providing a great flexibility in the inversion parametrization. First, in order to release the memory requirements, we developed our FWI algorithm in the frequency domain and take benefit of the wave-number redundancy in the seismic data to process a quite reduced number of frequencies. To do so, we extract frequency solutions from time marching techniques which are efficient for 3D structures. Moreover, this frequency approach permits a multi-resolution strategy by proceeding from low to high frequencies: the final model at one frequency is used as the starting model for the next frequency. This procedure overcomes partially the non-linear behavior of the inversion
Inverse Tomo-Lithography for Making Microscopic 3D Parts
NASA Technical Reports Server (NTRS)
White, Victor; Wiberg, Dean
2003-01-01
According to a proposal, basic x-ray lithography would be extended to incorporate a technique, called inverse tomography, that would enable the fabrication of microscopic three-dimensional (3D) objects. The proposed inverse tomo-lithographic process would make it possible to produce complex shaped, submillimeter-sized parts that would be difficult or impossible to make in any other way. Examples of such shapes or parts include tapered helices, paraboloids with axes of different lengths, and even Archimedean screws that could serve as rotors in microturbines. The proposed inverse tomo-lithographic process would be based partly on a prior microfabrication process known by the German acronym LIGA (lithographie, galvanoformung, abformung, which means lithography, electroforming, molding). In LIGA, one generates a precise, high-aspect ratio pattern by exposing a thick, x-ray-sensitive resist material to an x-ray beam through a mask that contains the pattern. One can electrodeposit metal into the developed resist pattern to form a precise metal part, then dissolve the resist to free the metal. Aspect ratios of 100:1 and patterns into resist thicknesses of several millimeters are possible.
Solution accelerators for large scale 3D electromagnetic inverse problems
Newman, Gregory A.; Boggs, Paul T.
2004-04-05
We provide a framework for preconditioning nonlinear 3D electromagnetic inverse scattering problems using nonlinear conjugate gradient (NLCG) and limited memory (LM) quasi-Newton methods. Key to our approach is the use of an approximate adjoint method that allows for an economical approximation of the Hessian that is updated at each inversion iteration. Using this approximate Hessian as a preconditoner, we show that the preconditioned NLCG iteration converges significantly faster than the non-preconditioned iteration, as well as converging to a data misfit level below that observed for the non-preconditioned method. Similar conclusions are also observed for the LM iteration; preconditioned with the approximate Hessian, the LM iteration converges faster than the non-preconditioned version. At this time, however, we see little difference between the convergence performance of the preconditioned LM scheme and the preconditioned NLCG scheme. A possible reason for this outcome is the behavior of the line search within the LM iteration. It was anticipated that, near convergence, a step size of one would be approached, but what was observed, instead, were step lengths that were nowhere near one. We provide some insights into the reasons for this behavior and suggest further research that may improve the performance of the LM methods.
NASA Astrophysics Data System (ADS)
Ullmann, A.; Scheunert, M.; Afanasjew, M.; Börner, R.-U.; Siemon, B.; Spitzer, K.
2016-07-01
As a standard procedure, multi-frequency helicopter-borne electromagnetic (HEM) data are inverted to conductivity-depth models using 1-D inversion methods, which may, however, fail in areas of strong lateral conductivity contrasts (so-called induction anomalies). Such areas require more realistic multi-dimensional modelling. Since the full 3-D inversion of an entire HEM data set is still extremely time consuming, our idea is to combine fast 1-D and accurate but numerically expensive 3-D inversion of HEM data in such a way that the full 3-D inversion is only carried out for those parts of a HEM survey which are affected by induction anomalies. For all other parts, a 1-D inversion method is sufficient. We present a newly developed algorithm for identification, selection, and extraction of induction anomalies in HEM data sets and show how the 3-D inversion model of the anomalous area is re-integrated into the quasi-1-D background. Our proposed method is demonstrated to work properly on a synthetic and a field HEM data set from the Cuxhaven tunnel valley in Germany. We show that our 1-D/3-D approach yields better results compared to 1-D inversions in areas where 3-D effects occur.
NASA Astrophysics Data System (ADS)
Keeling, Ryan Marc
The Arbuckle Group in northeastern Oklahoma consists of multiple carbonate formations, along with several relatively thin sandstone units. The group is a part of the "Great American Carbonate Bank" of the mid-continent and can be found regionally as far east as the Arkoma Basin in Arkansas, and as far west as the Anadarko Basin in Oklahoma. The Arbuckle is part of the craton-wide Sauk sequence, which is both underlain and overlain by regional unconformities. Arbuckle is not deposited directly on top of a source rock. In order for reservoirs within the Arbuckle to become charged with hydrocarbons, they must be juxtaposed against source rocks or along migration pathways. Inspired by the petroleum potential of proximal Arbuckle reservoirs and the lack of local stratigraphic understanding, this study aims to subdivide Arbuckle stratigraphy and identify porosity networks using 3D seismic within the study area of western Osage County, Oklahoma. These methods and findings can then be applied to petroleum exploration in Cambro-Ordovician carbonates in other localities. My research question is: Can the Arbuckle in SW Osage County be stratigraphically subdivided based on 3D seismic characteristics? This paper outlines the depositional environment of the Arbuckle, synthesizes previous studies and examines the Arbuckle as a petroleum system in Northeastern Oklahoma. The investigation includes an interpretation of intra-Arbuckle unconformities, areas of secondary porosity (specifically, sequence boundaries), and hydrocarbon potential of the Arbuckle Group using 3D seismic data interpretation with a cursory analysis of cored intervals.
3D modelling of Trompsburg Complex (in South Africa) using 3D focusing inversion of gravity data
NASA Astrophysics Data System (ADS)
Rezaie, Mohammad; Moradzadeh, Ali; Kalate, Ali Nejati; Aghajani, Hamid; Kahoo, Amin Roshandel; Moazam, Sahar
2017-06-01
The Trompsburg complex is a huge layered mafic igneous rock that is located near the town of Trompsburg in the Free State Province, South Africa that does not outcrop on the surface. Here, we construct 3D model of Trompsburg intrusion using 3D focusing inversion of gravity data. The inversion of gravity data is one of the most important topics in the quantitative interpretation of practical geophysical data. Focusing inversion can produce compact solution and recover the sharp boundaries between intrusive body and host rocks. In focusing inversion of Trompsburg gravity data we set focusing parameter equals 0.02. According to the geological information, lower density bound set to -0.1 g/cm3 and upper density bound set to 0.5 g/cm3. The results of 3D inversion in this study indicate that the Trompsburg Complex is a deep bowl-shaped intrusion which is extended to 33(km) below the surface. It is like an oval in horizontal plane sections with major axis of nearly 50 km in west- east direction and north- south minor axis about 30 km. The obtained results confirms that this complex could be related to intraplate magmatism.
NASA Astrophysics Data System (ADS)
Wright, A.; Kluesner, J. W.; Brothers, D. S.; Johnson, S. Y.
2015-12-01
Multiple submarine landslides have been previously documented on the north flank of the Santa Barbara Channel, and such failures are considered capable of generating local tsunamis. 2D seismic-reflection datasets provide a general view of regional framework geology, including faulting and folding associated with north-south compression. However, better understanding of the relationships between faults, folds, stratigraphic architecture, and submarine landslides can be obtained with 3D seismic datasets. In this study we use an industry 3D seismic-reflection volume that encompasses the slope and shelfbreak surrounding the Gaviota submarine landslide (3.8 km2) to investigate structural and stratigraphic controls on slope failure in this region. The depth-migrated seismic volume shows a network of stacked thrust faults, backthrusts, and splays that results in both broad and local zones of compression and folding along the slope and shelf. One localized zone of enhanced folding associated with small-offset thrust faults is located directly beneath the Gaviota landslide headwall, while another zone is located directly below an imaged seafloor fissure. In addition, 3D seismic attribute analysis provides insight into the shallow sedimentary section of the failed and non-failed sedimentary packages. Calculation of RMS amplitude and dominant frequency within a windowed region below the seafloor horizon delineates an apparent zone of gas-charged strata that onlaps onto older folded sediments. The up-dip limit of these gas-charged sediments aligns with the location of a seafloor fissure that extends westward from the Gaviota landslide headwall. We propose that the combination of deformation and fluid charging acted to pre-condition and trigger the failure of the Gaviota landslide, and as a result, the presence of these conditions along the fissure adjacent to the Gaviota landslide suggests this area should be considered landslide prone.
3D stochastic joint inversion of gravity and magnetic data
NASA Astrophysics Data System (ADS)
Shamsipour, Pejman; Marcotte, Denis; Chouteau, Michel
2012-04-01
A novel stochastic joint inversion method based on cokriging is applied to estimate density and magnetic susceptibility distributions from gravity and total magnetic field data. The method fully integrates the physical relations between density-gravity, on one hand, and magnetic susceptibility-total magnetic field, on the other hand. As a consequence, when the data are considered noise-free, the responses from the inverted density and susceptibility data exactly reproduce the observed data. The required density and magnetic susceptibility auto- and cross covariance are assumed to follow a linear model of coregionalization (LCM). The parameters of the LCM are estimated from v-v plot fitting of the gravity and total magnetic experimental covariances. The model is tested on two synthetic cases and one real data set, the Perseverance mine (Quebec, Canada). Joint inversions are compared to separate inversions. The joint inversions better recover the known models in the synthetic cases. With the real data set, better definition and location of the mineralized lenses are achieved by joint inversion.
3D stochastic inversion and joint inversion of potential fields for multi scale parameters
NASA Astrophysics Data System (ADS)
Shamsipour, Pejman
In this thesis we present the development of new techniques for the interpretation of potential field (gravity and magnetic data), which are the most widespread economic geophysical methods used for oil and mineral exploration. These new techniques help to address the long-standing issue with the interpretation of potential fields, namely the intrinsic non-uniqueness inversion of these types of data. The thesis takes the form of three papers (four including Appendix), which have been published, or soon to be published, in respected international journals. The purpose of the thesis is to introduce new methods based on 3D stochastical approaches for: 1) Inversion of potential field data (magnetic), 2) Multiscale Inversion using surface and borehole data and 3) Joint inversion of geophysical potential field data. We first present a stochastic inversion method based on a geostatistical approach to recover 3D susceptibility models from magnetic data. The aim of applying geostatistics is to provide quantitative descriptions of natural variables distributed in space or in time and space. We evaluate the uncertainty on the parameter model by using geostatistical unconditional simulations. The realizations are post-conditioned by cokriging to observation data. In order to avoid the natural tendency of the estimated structure to lay near the surface, depth weighting is included in the cokriging system. Then, we introduce algorithm for multiscale inversion, the presented algorithm has the capability of inverting data on multiple supports. The method involves four main steps: i. upscaling of borehole parameters (It could be density or susceptibility) to block parameters, ii. selection of block to use as constraints based on a threshold on kriging variance, iii. inversion of observation data with selected block densities as constraints, and iv. downscaling of inverted parameters to small prisms. Two modes of application are presented: estimation and simulation. Finally, a novel
An inverse method to retrieve 3D radar reflectivity composites
NASA Astrophysics Data System (ADS)
Roca-Sancho, Jordi; Berenguer, Marc; Sempere-Torres, Daniel
2014-11-01
Dense radar networks offer the possibility of getting better Quantitative Precipitation Estimates (QPE) than those obtained with individual radars, as they allow increasing the coverage and improving quality of rainfall estimates in overlapping areas. Well-known sources of error such as attenuation by intense rainfall or errors associated with range can be mitigated through radar composites. Many compositing techniques are devoted to operational uses and do not exploit all the information that the network is providing. In this work an inverse method to obtain high-resolution radar reflectivity composites is presented. The method uses a model of radar sampling of the atmosphere that accounts for path attenuation and radar measurement geometry. Two significantly different rainfall situations are used to show detailed results of the proposed inverse method in comparison to other existing methodologies. A quantitative evaluation is carried out in a 12 h-event using two independent sources of information: a radar not involved in the composition process and a raingauge network. The proposed inverse method shows better performance in retrieving high reflectivity values and reproducing variability at convective scales than existing methods.
A real-time moment-tensor inversion system (GRiD-MT-3D) using 3-D Green's functions
NASA Astrophysics Data System (ADS)
Nagao, A.; Furumura, T.; Tsuruoka, H.
2016-12-01
We developed a real-time moment-tensor inversion system using 3-D Green's functions (GRiD-MT-3D) by improving the current system (GRiD-MT; Tsuruoka et al., 2009), which uses 1-D Green's functions for longer periods than 20 s. Our moment-tensor inversion is applied to the real-time monitoring of earthquakes occurring beneath Kanto basin area. The basin, which is constituted of thick sediment layers, lies on the complex subduction of the Philippine-Sea Plate and the Pacific Plate that can significantly affect the seismic wave propagation. We compute 3-D Green's functions using finite-difference-method (FDM) simulations considering a 3-D velocity model, which is based on the Japan Integrated Velocity Structure Model (Koketsu et al., 2012), that includes crust, mantle, and subducting plates. The 3-D FDM simulations are computed over a volume of 468 km by 432 km by 120 km in the EW, NS, and depth directions, respectively, that is discretized into 0.25 km grids. Considering that the minimum S wave velocity of the sedimentary layer is 0.5 km/s, simulations can compute seismograms up to 0.5 Hz. We calculate Green's functions between 24,700 sources, which are distributed every 0.1° in the horizontal direction and every 9 km in depth direction, and 13 F-net stations. To compute this large number of Green's functions, we used the EIC parallel computer of ERI. The reciprocity theory, which switches the source and station positions, is used to reduce total computation costs. It took 156 hours to compute all the Green's functions. Results show that at long-periods (T>15 s), only small differences are observed between the 3-D and 1-D Green's functions as indicated by high correlation coefficients of 0.9 between the waveforms. However, at shorter periods (T<10 s), the differences become larger and the correlation coefficients drop to 0.5. The effect of the 3-D heterogeneous structure especially affects the Green's functions for the ray paths that across complex geological
Direct inversion of digital 3D Fraunhofer holography maps.
Podorov, Sergei G; Förster, Eckhart
2016-01-20
Differential Fourier holography (DFH) gives an exact mathematical solution of the inverse problem of diffraction in the Fraunhofer regime. After the first publication [Opt. Express15, 9954 (2007)], DFH was successfully applied in many experiments to obtain amplitude and phase information about two-dimensional images. In this paper, we demonstrate numerically the possibility to apply DFH also for investigation of unknown three-dimensional objects. The first simulation is made for a double-spiral structure plus a line as a reference object.
3D parallel inversion of time-domain airborne EM data
NASA Astrophysics Data System (ADS)
Liu, Yun-He; Yin, Chang-Chun; Ren, Xiu-Yan; Qiu, Chang-Kai
2016-12-01
To improve the inversion accuracy of time-domain airborne electromagnetic data, we propose a parallel 3D inversion algorithm for airborne EM data based on the direct Gauss-Newton optimization. Forward modeling is performed in the frequency domain based on the scattered secondary electrical field. Then, the inverse Fourier transform and convolution of the transmitting waveform are used to calculate the EM responses and the sensitivity matrix in the time domain for arbitrary transmitting waves. To optimize the computational time and memory requirements, we use the EM "footprint" concept to reduce the model size and obtain the sparse sensitivity matrix. To improve the 3D inversion, we use the OpenMP library and parallel computing. We test the proposed 3D parallel inversion code using two synthetic datasets and a field dataset. The time-domain airborne EM inversion results suggest that the proposed algorithm is effective, efficient, and practical.
NASA Astrophysics Data System (ADS)
Yan, Na; Mountney, Nigel P.; Colombera, Luca; Dorrell, Robert M.
2017-08-01
Although fundamental types of fluvial meander-bend transformations - expansion, translation, rotation, and combinations thereof - are widely recognised, the relationship between the migratory behaviour of a meander bend, and its resultant accumulated sedimentary architecture and lithofacies distribution remains relatively poorly understood. Three-dimensional data from both currently active fluvial systems and from ancient preserved successions known from outcrop and subsurface settings are limited. To tackle this problem, a 3D numerical forward stratigraphic model - the Point-Bar Sedimentary Architecture Numerical Deduction (PB-SAND) - has been devised as a tool for the reconstruction and prediction of the complex spatio-temporal migratory evolution of fluvial meanders, their generated bar forms and the associated lithofacies distributions that accumulate as heterogeneous fluvial successions. PB-SAND uses a dominantly geometric modelling approach supplemented by process-based and stochastic model components, and is constrained by quantified sedimentological data derived from modern point bars or ancient successions that represent suitable analogues. The model predicts the internal architecture and geometry of fluvial point-bar elements in three dimensions. The model is applied to predict the sedimentary lithofacies architecture of ancient preserved point-bar and counter-point-bar deposits of the middle Jurassic Scalby Formation (North Yorkshire, UK) to demonstrate the predictive capabilities of PB-SAND in modelling 3D architectures of different types of meander-bend transformations. PB-SAND serves as a practical tool with which to predict heterogeneity in subsurface hydrocarbon reservoirs and water aquifers.
NASA Astrophysics Data System (ADS)
Portal, Angélie; Fargier, Yannick; Lénat, Jean-François; Labazuy, Philippe
2016-04-01
The electrical resistivity tomography (ERT) method, initially developed for environmental and engineering exploration, is now commonly used for geological structures imaging. Such structures can present complex characteristics that conventional 2D inversion processes cannot perfectly integrate. Here we present a new 3D inversion algorithm named EResI, firstly developed for levee investigation, and presently applied to the study of a complex lava dome (the Puy de Dôme volcano, France). EResI algorithm is based on a conventional regularized Gauss-Newton inversion scheme and a 3D non-structured discretization of the model (double grid method based on tetrahedrons). This discretization allows to accurately model the topography of investigated structure (without a mesh deformation procedure) and also permits a precise location of the electrodes. Moreover, we demonstrate that a complete 3D unstructured discretization limits the number of inversion cells and is better adapted to the resolution capacity of tomography than a structured discretization. This study shows that a 3D inversion with a non-structured parametrization has some advantages compared to classical 2D inversions. The first advantage comes from the fact that a 2D inversion leads to artefacts due to 3D effects (3D topography, 3D internal resistivity). The second advantage comes from the fact that the capacity to experimentally align electrodes along an axis (for 2D surveys) depends on the constrains on the field (topography...). In this case, a 2D assumption induced by 2.5D inversion software prevents its capacity to model electrodes outside this axis leading to artefacts in the inversion result. The last limitation comes from the use of mesh deformation techniques used to accurately model the topography in 2D softwares. This technique used for structured discretization (Res2dinv) is prohibed for strong topography (>60 %) and leads to a small computational errors. A wide geophysical survey was carried out
NASA Astrophysics Data System (ADS)
Wright, A.; Brothers, D. S.; Kluesner, J.; Johnson, S. Y.
2016-12-01
Multiple submarine landslides have been documented on the north flank of the Santa Barbara Basin and such failures are considered capable of generating local tsunami hazards to the Santa Barbara region. Past 2D seismic reflection data has provided a general view of the regional framework geology resulting from north-south compression, but fails to identify along-strike variations of faults and folds. This study uses industry 3D seismic reflection data encompassing the slope surrounding the 3.8 km2-Gaviota submarine landslide to investigate structural and stratigraphic controls of slope failure in this region. The 3D depth-migrated volume shows a complex network of faults that result in both broad and local zones of compression, folding, and uplift along the slope. One localized zone of enhanced anticlinal folding and uplift associated with small-scale thrust faults is located directly beneath the Gaviota slide, while another is beneath a seafloor fissure west of the slide inferred to represent incipient failure. New high-resolution 2D transects constrain the character of shallow deformation above the locally uplifted blocks. 3D isopach maps indicate the seafloor fissures trend along a key threshold of thickness between the seafloor and a shallow horizon; the fissures are also coincide with an apparent zone of shallow, gas-charged strata that onlap the steeply dipping flanks of local anticlinal deformation. Because the seafloor gradient near the Gaviota slide is significantly lower than the internal friction angle for fine-grained marine sediments, we propose that a combination of active deformation, sediment compaction, and gas charging acted to precondition the slope of the Gaviota landslide for failure by reducing the shear strength. Similar factors occur beneath intact sections of the slope adjacent to the slide, which should be considered prone to future landsliding.
Rodriguez, Brian D.; Sweetkind, Donald S.
2015-01-01
The 3-D inversion was generally able to reproduce the gross resistivity structure of the “known” model, but the simulated conductive volcanic composite unit horizons were often too shallow when compared to the “known” model. Additionally, the chosen computation parameters such as station spacing appear to have resulted in computational artifacts that are difficult to interpret but could potentially be removed with further refinements of the 3-D resistivity inversion modeling technique.
Levander, Alan R.
2004-12-01
Under ER63662, 3-D Seismic Experimentation and Advanced Processing/Inversion Development for Investigations of the Shallow Subsurface, we have completed a number of subprojects associated with the Hill Air Force Base (HAFB) high resolution 3-D reflection/tomography dataset.
NASA Astrophysics Data System (ADS)
Fadel, I.; van der Meijde, M.; Kerle, N.
2013-12-01
Non-uniqueness of satellite gravity interpretation has been usually reduced by using a priori information from various sources, e.g. seismic tomography models. The reduction in non-uniqueness has been based on velocity-density conversion formulas or user interpretation for 3D subsurface structures (objects) in seismic tomography models. However, these processes introduce additional uncertainty through the conversion relations due to the dependency on the other physical parameters such as temperature and pressure, or through the bias in the interpretation due to user choices and experience. In this research, a new methodology is introduced to extract the 3D subsurface structures from 3D geophysical data using a state-of-art 3D Object Oriented Image Analysis (OOA) technique. 3D OOA is tested using a set of synthetic models that simulate the real situation in the study area of this research. Then, 3D OOA is used to extract 3D subsurface objects from a real 3D seismic tomography model. The extracted 3D objects are used to reconstruct a forward model and its response is compared with the measured satellite gravity. Finally, the result of the forward modelling, based on the extracted 3D objects, is used to constrain the inversion process of satellite gravity data. Through this work, a new object-based approach is introduced to interpret and extract the 3D subsurface objects from 3D geophysical data. This can be used to constrain modelling and inversion of potential field data using the extracted 3D subsurface structures from other methods. In summary, a new approach is introduced to constrain inversion of satellite gravity measurements and enhance interpretation capabilities.
NASA Astrophysics Data System (ADS)
Rezaie, Mohammad; Moradzadeh, Ali; Kalate, Ali Nejati; Aghajani, Hamid
2017-01-01
Inversion of gravity data is one of the important steps in the interpretation of practical data. One of the most interesting geological frameworks for gravity data inversion is the detection of sharp boundaries between orebody and host rocks. The focusing inversion is able to reconstruct a sharp image of the geological target. This technique can be efficiently applied for the quantitative interpretation of gravity data. In this study, a new reweighted regularized method for the 3D focusing inversion technique based on Lanczos bidiagonalization method is developed. The inversion results of synthetic data show that the new method is faster than common reweighted regularized conjugate gradient method to produce an acceptable solution for focusing inverse problem. The new developed inversion scheme is also applied for inversion of the gravity data collected over the San Nicolas Cu-Zn orebody in Zacatecas State, Mexico. The inversion results indicate a remarkable correlation with the true structure of the orebody that is achieved from drilling data.
3-D cross-gradient joint inversion of seismic refraction and DC resistivity data
NASA Astrophysics Data System (ADS)
Shi, Zhanjie; Hobbs, Richard W.; Moorkamp, Max; Tian, Gang; Jiang, Lu
2017-06-01
We present a 3-D cross-gradient joint inversion algorithm for seismic refraction and DC resistivity data. The structural similarity between seismic slowness and resistivity models is enforced by a cross-gradient term in the objective function that also includes misfit and regularization terms. A limited memory quasi-Newton approach is used to perform the optimization of the objective function. To validate the proposed methodology and its implementation, tests were performed on a typical archaeological geophysical synthetic model. The results show that the inversion model and physical parameters estimated by our joint inversion method are more consistent with the true model than those from single inversion algorithm. Moreover, our approach appears to be more robust in conditions of noise. Finally, the 3-D cross-gradient joint inversion algorithm was applied to the field data from Lin_an ancient city site in Hangzhou of China. The 3-D cross-gradient joint inversion models are consistent with the archaeological excavation results of the ancient city wall remains. However, by single inversion, seismic slowness model does not show the anomaly of city wall remains and resistivity model does not fit well with the archaeological excavation results. Through these comparisons, we conclude that the proposed algorithm can be used to jointly invert 3-D seismic refraction and DC resistivity data to reduce the uncertainty brought by single inversion scheme.
NASA Astrophysics Data System (ADS)
Laurent, Dimitri; Picot, Marie; Marsset, Tania; Droz, Laurence; Rabineau, Marina; Granjeon, Didier; Molliex, Stéphane
2017-04-01
The geometry and internal functioning of turbidite systems are relatively well-constrained today. However, the respective role of autogenic (topographic compensation, dynamics of turbidity currents…) and allogenic factors (tectonics, sea-level, climate) governing their architectural evolution is still under debate. The geometry of the Quaternary Congo Fan is characterized by successive sedimentary prograding/retrograding cycles bounded by upfan avulsions, reflecting a periodic control of sedimentation (Picot et al., 2016). Multi-proxy studies revealed a strong interplay between autogenic control and climate forcing as evidenced by changes in fluvial sediment supplies consistent with arid and humid periods in the Congo River Basin. In the light of these results, the aim of this study is to investigate the relative impact of internal and external forcing factors controlling, both in time and space, the formation and evolution of depocenters of the Congo Deep-Sea Fan since 210 ka. This work represents the first attempt to model in 3D the stratigraphic architecture of the Congo turbidite system using DionisosFlow (IFP-EN), a diffusion process-based software. It allows the simulation of sediment transport and the 3D geometry reproduction of sedimentary units based on physical processes such as sea level changes, tectonics, sediment supply and transport. According to the modeling results, the role of topographic compensation in the deep-sea fan geometry is secondary compared to climate changes in the drainage basin. It appears that a periodic variation of sediment discharge and water flow is necessary to simulate the timing and volume of prograding/retrograding sedimentary cycles and more particularly the upfan avulsion events. The best-fit simulations show that the overriding factor for such changes corresponds to the expansion of the vegetation cover in the catchment basin associated to the Milankovitch cycle of precession which controlled the West African Monsoon
3D Propagation and Geoacoustic Inversion Studies in the Mid-Atlantic Bight
2016-06-07
3D Propagation and Geoacoustic Inversion Studies in the Mid-Atlantic Bight Kevin B. Smith Code PH/Sk, Department of Physics Naval Postgraduate...properties and measured transmission loss. Results from this analysis will be considered in the context of geoacoustic inversions . OBJECTIVES To...bathymetric features and ocean fronts near the shelf break of the mid-Atlantic Bight, and use of various data for geoacoutic inversion studies. The results
Rodriguez, Brian D.
2017-03-31
This report summarizes the results of three-dimensional (3-D) resistivity inversion simulations that were performed to account for local 3-D distortion of the electric field in the presence of 3-D regional structure, without any a priori information on the actual 3-D distribution of the known subsurface geology. The methodology used a 3-D geologic model to create a 3-D resistivity forward (“known”) model that depicted the subsurface resistivity structure expected for the input geologic configuration. The calculated magnetotelluric response of the modeled resistivity structure was assumed to represent observed magnetotelluric data and was subsequently used as input into a 3-D resistivity inverse model that used an iterative 3-D algorithm to estimate 3-D distortions without any a priori geologic information. A publicly available inversion code, WSINV3DMT, was used for all of the simulated inversions, initially using the default parameters, and subsequently using adjusted inversion parameters. A semiautomatic approach of accounting for the static shift using various selections of the highest frequencies and initial models was also tested. The resulting 3-D resistivity inversion simulation was compared to the “known” model and the results evaluated. The inversion approach that produced the lowest misfit to the various local 3-D distortions was an inversion that employed an initial model volume resistivity that was nearest to the maximum resistivities in the near-surface layer.
A fast and low-loss 3-D magnetotelluric inversion method with parallel structure
NASA Astrophysics Data System (ADS)
Zhang, K.; Zhang, L.
2013-12-01
The 2D assumption is valid in some cases of interpretation, the approximation does not work in most cases, especially in areas with complex geo-electrical structure. A number of 3D magentotelluric inversion methods has been proposed, including RRI, CG, QA, NLCG. Each of those methods has its own advantages and disadvantages. However, as the 3D dataset and mesh grid require greater computer memory and calculation time than 2D methods, the efficiency of the inversion scheme become a key concern of 3D inversions. We chose NLCG as the optimization method for inversion. A parameter matrix related with the current resisitivity model and data error is proposed to approximate the Hessian matrix. So four forward calculation can be avoided each iteration. In addition, OPENMP parallel API is utilized to establish an effecient parallel inversion structure based on frequency to reduce computation time. And both synthetic and field data are used to test the efficiency of the inversion and the preconditioning method. The model consists of four square prisms residing in a halfspace. The total computation time of invertion is 706s (use one PC). Fiugre 1 shows the inversion result. The abnormal bodies can be distinguished clearly. Field data from the NIHE dataset in China is used to verify the reliability and efficiency of the 3D inversion method. The total computation time is about 25 minutes after 60 iterations on one PC. Totally, four electrical layers can be corresponded to the four stratum in 3D AMT inversion model, and the faults can be seen clearly. In addition, we can get more information about fault and alteration interface from constrained inversion result. Finally, the inversion method is very fast and low-loss, so it can be used in modern PC (need only one PC) with few hardware constraints. (a): initial model; (b): inversion depth slices (1-4km); (c): fitting error (a): AMT 3D slice; (b): CSAMT 2D model; (c): TEM 1D model; (d): SIP 2D model; (e) AMT 3D constrained
NASA Astrophysics Data System (ADS)
Simutė, S.; Fichtner, A.
2015-12-01
We present a feasibility study for seismic source inversions using a 3-D velocity model for the Japanese Islands. The approach involves numerically calculating 3-D Green's tensors, which is made efficient by exploiting Green's reciprocity. The rationale for 3-D seismic source inversion has several aspects. For structurally complex regions, such as the Japan area, it is necessary to account for 3-D Earth heterogeneities to prevent unknown structure polluting source solutions. In addition, earthquake source characterisation can serve as a means to delineate existing faults. Source parameters obtained for more realistic Earth models can then facilitate improvements in seismic tomography and early warning systems, which are particularly important for seismically active areas, such as Japan. We have created a database of numerically computed 3-D Green's reciprocals for a 40°× 40°× 600 km size area around the Japanese Archipelago for >150 broadband stations. For this we used a regional 3-D velocity model, recently obtained from full waveform inversion. The model includes attenuation and radial anisotropy and explains seismic waveform data for periods between 10 - 80 s generally well. The aim is to perform source inversions using the database of 3-D Green's tensors. As preliminary steps, we present initial concepts to address issues that are at the basis of our approach. We first investigate to which extent Green's reciprocity works in a discrete domain. Considering substantial amounts of computed Green's tensors we address storage requirements and file formatting. We discuss the importance of the initial source model, as an intelligent choice can substantially reduce the search volume. Possibilities to perform a Bayesian inversion and ways to move to finite source inversion are also explored.
Spontaneous mirror-symmetry breaking induces inverse energy cascade in 3D active fluids
Słomka, Jonasz; Dunkel, Jörn
2017-01-01
Classical turbulence theory assumes that energy transport in a 3D turbulent flow proceeds through a Richardson cascade whereby larger vortices successively decay into smaller ones. By contrast, an additional inverse cascade characterized by vortex growth exists in 2D fluids and gases, with profound implications for meteorological flows and fluid mixing. The possibility of a helicity-driven inverse cascade in 3D fluids had been rejected in the 1970s based on equilibrium-thermodynamic arguments. Recently, however, it was proposed that certain symmetry-breaking processes could potentially trigger a 3D inverse cascade, but no physical system exhibiting this phenomenon has been identified to date. Here, we present analytical and numerical evidence for the existence of an inverse energy cascade in an experimentally validated 3D active fluid model, describing microbial suspension flows that spontaneously break mirror symmetry. We show analytically that self-organized scale selection, a generic feature of many biological and engineered nonequilibrium fluids, can generate parity-violating Beltrami flows. Our simulations further demonstrate how active scale selection controls mirror-symmetry breaking and the emergence of a 3D inverse cascade. PMID:28193853
Lithologic identification & mapping test based on 3D inversion of magnetic and gravity
NASA Astrophysics Data System (ADS)
Yan, Jiayong; Lv, Qingtian; Qi, Guang; Zhao, Jinhua; Zhang, Yongqian
2016-04-01
Though lithologic identification & mapping to achieve ore concentration district transparent within 5km depth is the main way to realize deep fine structures study, to explore deep mineral resources and to reveal metallogenic regularity of large-scale ore district . Owing to the wide covered area, high sampling density and mature three-dimensional inversion algorithm of gravity and magnetic data, so gravity and magnetic inversion become the most likely way to achieve three-dimensional lithologic mapping at the present stage. In this paper, we take Lu-zong(Lujiang county to Zongyang county in Anhui province ,east China) ore district as a case, we proposed lithologic mapping flow based 3D inversion of gravity magnetic and then carry out the lithologic mapping test. Lithologic identification & mapping flow is as follows: 1. Analysis relations between lithology and density and magnetic susceptibility by cross plot. 2.Extracting appropriate residual anomalies from high-precision Bourger gravity and aeromagnetic. 3.Use same mesh, do 3D magnetic and gravity inversion respectively under prior information constrained, and then invert susceptibility and density 3D model. 4. According setp1, construct logical topology operations between density 3D model and susceptibility. 5.Use the logical operations, identify lithogies cell by cell in 3D mesh, and then get 3D lithological model. According this flow, we obtained three-dimensional distribution of five main type lithologies in the Lu-Zong ore district within 5km depth. The result of lithologic mapping not only showed that the shallow characteristics and surface geological mapping are basically Coincide,more importantly ,it reveals the deeper lithologic changes.The lithlogical model make up the insufficient of surface geological mapping. The lithologic mapping test results in Lu-Zong ore concentration district showed that lithological mapping using 3D inversion of gravity and magnetic is a effective method to reveal the
3D Airborne Electromagnetic Inversion: A case study from the Musgrave Region, South Australia
NASA Astrophysics Data System (ADS)
Cox, L. H.; Wilson, G. A.; Zhdanov, M. S.; Sunwall, D. A.
2012-12-01
Geophysicists know and accept that geology is inherently 3D, and is resultant from complex, overlapping processes related to genesis, metamorphism, deformation, alteration, weathering, and/or hydrogeology. Yet, the geophysics community has long relied on qualitative analysis, conductivity depth imaging (CDIs), 1D inversion, and/or plate modeling. There are many reasons for this deficiency, not the least of which has been the lack of capacity for historic 3D AEM inversion algorithms to invert entire surveys so as to practically affect exploration decisions. Our recent introduction of a moving sensitivity domain (footprint) methodology has been a paradigm shift in AEM interpretation. The basis of this method is that one needs only to calculate the responses and sensitivities for that part of the 3D earth model that is within the AEM system's sensitivity domain (footprint), and then superimpose all sensitivity domains into a single, sparse sensitivity matrix for the entire 3D earth model which is then updated in a regularized inversion scheme. This has made it practical to rigorously invert entire surveys with thousands of line kilometers of AEM data to mega-cell 3D models in hours using multi-processor workstations. Since 2010, over eighty individual projects have been completed for Aerodat, AEROTEM, DIGHEM, GEOTEM, HELITEM, HoisTEM, MEGATEM, RepTEM, RESOLVE, SkyTEM, SPECTREM, TEMPEST, and VTEM data from Australia, Brazil, Canada, Finland, Ghana, Peru, Tanzania, the US, and Zambia. Examples of 3D AEM inversion have been published for a variety of applications, including mineral exploration, oil sands exploration, salinity, permafrost, and bathymetry mapping. In this paper, we present a comparison of 3D inversions for SkyTEM, SPECTREM, TEMPET and VTEM data acquired over the same area in the Musgrave region of South Australia for exploration under cover.
3-D joint inversion of the magnetotelluric phase tensor and vertical magnetic transfer functions
NASA Astrophysics Data System (ADS)
Tietze, Kristina; Ritter, Oliver; Egbert, Gary D.
2015-11-01
With advancing computational resources, 3-D inversion techniques have become feasible in recent years and are now a more widely used tool for magnetotelluric (MT) data interpretation. Galvanic distortion caused by small-scale near-surface inhomogeneities remains an obstacle for 3-D MT inversion which so far has experienced little attention. If not considered properly, the effect on 3-D inversion can be immense and result in erroneous subsurface models and interpretations. To tackle the problem we implemented inversion of the distortion-free phase tensor into the ModEM inversion package. The dimensionless phase tensor components describe only variations of the conductivity structure. When inverting these data, particular care has to be taken of the conductivity structure in the a priori model, which provides the reference frame when transferring the information from phase tensors into absolute conductivity values. Our results obtained with synthetic data show that phase tensor inversion can recover the regional conductivity structure in presence of galvanic distortion if the a priori model provides a reasonable assumption for the regional resistivity average. Joint inversion of phase tensor data and vertical magnetic transfer functions improves recovery of the absolute resistivity structure and is less dependent on the prior model. We also used phase tensor inversion for a data set of more than 250 MT sites from the central San Andreas fault, California, where a number of sites showed significant galvanic distortion. We find the regional structure of the phase tensor inversion results compatible with previously obtained models from impedance inversion. In the vicinity of distorted sites, phase tensor inversion models exhibit more homogeneous/smoother conductivity structures.
2010-09-01
lithosphere elude us. We have been able to surmise that geologic variations here are substantial, and we know that they frustrate attempts to use robust...concepts are summarized conceptually in Figure 2, which shows the regions of the lithosphere most sensitive to the different data that we employ. To...construct an approximate 3D model of the lithosphere , we use a hybrid 1D-3D inversion. In many tomography analyses, dispersion variations are
Laplace-domain waveform modeling and inversion for the 3D acoustic-elastic coupled media
NASA Astrophysics Data System (ADS)
Shin, Jungkyun; Shin, Changsoo; Calandra, Henri
2016-06-01
Laplace-domain waveform inversion reconstructs long-wavelength subsurface models by using the zero-frequency component of damped seismic signals. Despite the computational advantages of Laplace-domain waveform inversion over conventional frequency-domain waveform inversion, an acoustic assumption and an iterative matrix solver have been used to invert 3D marine datasets to mitigate the intensive computing cost. In this study, we develop a Laplace-domain waveform modeling and inversion algorithm for 3D acoustic-elastic coupled media by using a parallel sparse direct solver library (MUltifrontal Massively Parallel Solver, MUMPS). We precisely simulate a real marine environment by coupling the 3D acoustic and elastic wave equations with the proper boundary condition at the fluid-solid interface. In addition, we can extract the elastic properties of the Earth below the sea bottom from the recorded acoustic pressure datasets. As a matrix solver, the parallel sparse direct solver is used to factorize the non-symmetric impedance matrix in a distributed memory architecture and rapidly solve the wave field for a number of shots by using the lower and upper matrix factors. Using both synthetic datasets and real datasets obtained by a 3D wide azimuth survey, the long-wavelength component of the P-wave and S-wave velocity models is reconstructed and the proposed modeling and inversion algorithm are verified. A cluster of 80 CPU cores is used for this study.
Development of direct-inverse 3-D methods for applied aerodynamic design and analysis
NASA Technical Reports Server (NTRS)
Carlson, Leland A.
1988-01-01
Several inverse methods have been compared and initial results indicate that differences in results are primarily due to coordinate systems and fuselage representations and not to design procedures. Further, results from a direct-inverse method that includes 3-D wing boundary layer effects, wake curvature, and wake displacement are presented. These results show that boundary layer displacements must be included in the design process for accurate results.
A MATLAB based 3D modeling and inversion code for MT data
NASA Astrophysics Data System (ADS)
Singh, Arun; Dehiya, Rahul; Gupta, Pravin K.; Israil, M.
2017-07-01
The development of a MATLAB based computer code, AP3DMT, for modeling and inversion of 3D Magnetotelluric (MT) data is presented. The code comprises two independent components: grid generator code and modeling/inversion code. The grid generator code performs model discretization and acts as an interface by generating various I/O files. The inversion code performs core computations in modular form - forward modeling, data functionals, sensitivity computations and regularization. These modules can be readily extended to other similar inverse problems like Controlled-Source EM (CSEM). The modular structure of the code provides a framework useful for implementation of new applications and inversion algorithms. The use of MATLAB and its libraries makes it more compact and user friendly. The code has been validated on several published models. To demonstrate its versatility and capabilities the results of inversion for two complex models are presented.
Seismic moment tensor inversion using a 3-D structural model: applications for the Australian region
NASA Astrophysics Data System (ADS)
Hingee, Myall; Tkalčić, Hrvoje; Fichtner, Andreas; Sambridge, Malcolm
2011-02-01
There is significant seismic activity in the region around Australia, largely due to the plate boundaries to the north and to the east of the mainland. This activity results in serious seismic and tsunami hazard in the coastal areas of Australia. Hence seismicity is and will be monitored in real time by Geoscience Australia (GA), which uses a network of permanent broadband seismometers. Seismic moment tensor (MT) solutions are currently determined using 1-D, radially symmetric models of Earth and this requires augmentation by recording stations located outside of Australia. A 3-D model of the Australian continent developed recently using full waveform tomography now offers the opportunity to significantly improve the determination of MT solutions of earthquakes from tectonically active regions. A complete-waveform, time-domain MT inversion method has been developed using a point-source approximation. A series of synthetic tests using first a 1-D and then a 3-D structural model has been performed. The feasibility of deploying 3-D versus 1-D Earth structure for the inversion of seismic data has been studied and the advantages of using the 3-D structural model were illustrated with examples. The 3-D model is superior to the 1-D model, as a number of sensitivity tests show. The ultimate goal of this work is an automated MT inversion system in Australia relying on GA and other international stations, although more work remains to be done before the full implementation of such a scheme in real time.
NASA Astrophysics Data System (ADS)
Lee, Eun Young; Novotny, Johannes; Wagreich, Michael
2015-04-01
In recent years, 3D visualization of sedimentary basins has become increasingly popular. Stratigraphic and structural mapping is highly important to understand the internal setting of sedimentary basins. And subsequent subsidence analysis provides significant insights for basin evolution. This study focused on developing a simple and user-friendly program which allows geologists to analyze and model sedimentary basin data. The developed program is aimed at stratigraphic and subsidence modelling of sedimentary basins from wells or stratigraphic profile data. This program is mainly based on two numerical methods; surface interpolation and subsidence analysis. For surface visualization four different interpolation techniques (Linear, Natural, Cubic Spline, and Thin-Plate Spline) are provided in this program. The subsidence analysis consists of decompaction and backstripping techniques. The numerical methods are computed in MATLAB® which is a multi-paradigm numerical computing environment used extensively in academic, research, and industrial fields. This program consists of five main processing steps; 1) setup (study area and stratigraphic units), 2) loading of well data, 3) stratigraphic modelling (depth distribution and isopach plots), 4) subsidence parameter input, and 5) subsidence modelling (subsided depth and subsidence rate plots). The graphical user interface intuitively guides users through all process stages and provides tools to analyse and export the results. Interpolation and subsidence results are cached to minimize redundant computations and improve the interactivity of the program. All 2D and 3D visualizations are created by using MATLAB plotting functions, which enables users to fine-tune the visualization results using the full range of available plot options in MATLAB. All functions of this program are illustrated with a case study of Miocene sediments in the Vienna Basin. The basin is an ideal place to test this program, because sufficient data is
Shentu, Nanying; Qiu, Guohua; Li, Qing; Tong, Renyuan; Shentu, Nankai; Wang, Yanjie
2015-04-13
Underground displacement monitoring is a key means to monitor and evaluate geological disasters and geotechnical projects. There exist few practical instruments able to monitor subsurface horizontal and vertical displacements simultaneously due to monitoring invisibility and complexity. A novel underground displacement 3D measuring sensor had been proposed in our previous studies, and great efforts have been taken in the basic theoretical research of underground displacement sensing and measuring characteristics by virtue of modeling, simulation and experiments. This paper presents an innovative underground displacement joint inversion method by mixing a specific forward modeling approach with an approximate optimization inversion procedure. It can realize a joint inversion of underground horizontal displacement and vertical displacement for the proposed 3D sensor. Comparative studies have been conducted between the measured and inversed parameters of underground horizontal and vertical displacements under a variety of experimental and inverse conditions. The results showed that when experimentally measured horizontal displacements and vertical displacements are both varied within 0~30 mm, horizontal displacement and vertical displacement inversion discrepancies are generally less than 3 mm and 1 mm, respectively, under three kinds of simulated underground displacement monitoring circumstances. This implies that our proposed underground displacement joint inversion method is robust and efficient to predict the measuring values of underground horizontal and vertical displacements for the proposed sensor.
Research on Joint Parameter Inversion for an Integrated Underground Displacement 3D Measuring Sensor
Shentu, Nanying; Qiu, Guohua; Li, Qing; Tong, Renyuan; Shentu, Nankai; Wang, Yanjie
2015-01-01
Underground displacement monitoring is a key means to monitor and evaluate geological disasters and geotechnical projects. There exist few practical instruments able to monitor subsurface horizontal and vertical displacements simultaneously due to monitoring invisibility and complexity. A novel underground displacement 3D measuring sensor had been proposed in our previous studies, and great efforts have been taken in the basic theoretical research of underground displacement sensing and measuring characteristics by virtue of modeling, simulation and experiments. This paper presents an innovative underground displacement joint inversion method by mixing a specific forward modeling approach with an approximate optimization inversion procedure. It can realize a joint inversion of underground horizontal displacement and vertical displacement for the proposed 3D sensor. Comparative studies have been conducted between the measured and inversed parameters of underground horizontal and vertical displacements under a variety of experimental and inverse conditions. The results showed that when experimentally measured horizontal displacements and vertical displacements are both varied within 0 ~ 30 mm, horizontal displacement and vertical displacement inversion discrepancies are generally less than 3 mm and 1 mm, respectively, under three kinds of simulated underground displacement monitoring circumstances. This implies that our proposed underground displacement joint inversion method is robust and efficient to predict the measuring values of underground horizontal and vertical displacements for the proposed sensor. PMID:25871714
NASA Astrophysics Data System (ADS)
Wang, Tai-Han; Huang, Da-Nian; Ma, Guo-Qing; Meng, Zhao-Hai; Li, Ye
2017-06-01
With the continuous development of full tensor gradiometer (FTG) measurement techniques, three-dimensional (3D) inversion of FTG data is becoming increasingly used in oil and gas exploration. In the fast processing and interpretation of large-scale high-precision data, the use of the graphics processing unit process unit (GPU) and preconditioning methods are very important in the data inversion. In this paper, an improved preconditioned conjugate gradient algorithm is proposed by combining the symmetric successive over-relaxation (SSOR) technique and the incomplete Choleksy decomposition conjugate gradient algorithm (ICCG). Since preparing the preconditioner requires extra time, a parallel implement based on GPU is proposed. The improved method is then applied in the inversion of noisecontaminated synthetic data to prove its adaptability in the inversion of 3D FTG data. Results show that the parallel SSOR-ICCG algorithm based on NVIDIA Tesla C2050 GPU achieves a speedup of approximately 25 times that of a serial program using a 2.0 GHz Central Processing Unit (CPU). Real airborne gravity-gradiometry data from Vinton salt dome (southwest Louisiana, USA) are also considered. Good results are obtained, which verifies the efficiency and feasibility of the proposed parallel method in fast inversion of 3D FTG data.
3-D Inverse Teleseismic Scattered Wave Imaging using the Kirchhoff Approximation
NASA Astrophysics Data System (ADS)
Liu, K.; Levander, A.
2012-04-01
We have developed a 3-D teleseismic imaging technique for scattered elastic wavefields using the Kirchhoff approximation. Kirchhoff migration/inversion have been well developed in exploration seismology within the inverse scattering framework (e.g. Miller et al., 1987; Beylkin and Burridge, 1990) to image subsurface structure that generates secondary wavefields caused by localized heterogeneities. Application of this method in global seismology has been largely limited to 2-D images made with 1-D reference models due to high computational cost and the lack of adequately dense receiver arrays (Bostock, 2002, Poppeliers and Pavlis, 2003; Frederiksen and Revenaugh, 2004; Cao et al., 2010). The deployment of the USArray Transportable and Flexible arrays in the United States and dense array recordings in other countries motivate developing teleseismic scattered wavefield imaging with the Kirchhoff approximation for 3-D velocity models for both scalar and vector wavefields to improve upper mantle imaging. Following Bostock's development of the 2-D problem (2002), we derive the 3-D P-to-S scattering inversion formula by phrasing the inverse problem in terms of the generalized Radon transform (GRT) and singular functions of discontinuity surfaces. In the forward scattering modeling, we extend the method to utilize a 3-D migration velocity model by calculating 3-D finite-difference traveltimes, backprojected from the receivers using an eikonal solver. To demonstrate the relative accuracy of the inversion, we examine several synthetic cases with a variety of discontinuity surfaces (sinuous, dipping, dome- and crater-shaped discontinuity interfaces, point scatterers, etc.). The Kirchhoff GRT imaging can successfully recover the shapes of these structures very well. We compare our Kirchhoff approximation imaging with the Born-approximate results, as well as the common-conversion point (CCP) stacked receiver function imaging for the various synthetic cases, and show a field
3D CSEM inversion based on goal-oriented adaptive finite element method
NASA Astrophysics Data System (ADS)
Zhang, Y.; Key, K.
2016-12-01
We present a parallel 3D frequency domain controlled-source electromagnetic inversion code name MARE3DEM. Non-linear inversion of observed data is performed with the Occam variant of regularized Gauss-Newton optimization. The forward operator is based on the goal-oriented finite element method that efficiently calculates the responses and sensitivity kernels in parallel using a data decomposition scheme where independent modeling tasks contain different frequencies and subsets of the transmitters and receivers. To accommodate complex 3D conductivity variation with high flexibility and precision, we adopt the dual-grid approach where the forward mesh conforms to the inversion parameter grid and is adaptively refined until the forward solution converges to the desired accuracy. This dual-grid approach is memory efficient, since the inverse parameter grid remains independent from fine meshing generated around the transmitter and receivers by the adaptive finite element method. Besides, the unstructured inverse mesh efficiently handles multiple scale structures and allows for fine-scale model parameters within the region of interest. Our mesh generation engine keeps track of the refinement hierarchy so that the map of conductivity and sensitivity kernel between the forward and inverse mesh is retained. We employ the adjoint-reciprocity method to calculate the sensitivity kernels which establish a linear relationship between changes in the conductivity model and changes in the modeled responses. Our code uses a direcy solver for the linear systems, so the adjoint problem is efficiently computed by re-using the factorization from the primary problem. Further computational efficiency and scalability is obtained in the regularized Gauss-Newton portion of the inversion using parallel dense matrix-matrix multiplication and matrix factorization routines implemented with the ScaLAPACK library. We show the scalability, reliability and the potential of the algorithm to deal with
3D inversion of aeromagnetic Data on Las Tablas District, Panama
NASA Astrophysics Data System (ADS)
Batista-Rodríguez, José A.; Caballero, Alberto; Pérez-Flores, Marco A.; Almaguer-Carmenates, Yuri
2017-03-01
We present a 3D model of Las Tablas District, Panama, obtained from the 3D inversion of aeromagnetic data, and constrained with information from surface geology, water wells and topography. The 3D model suggests the location, boundary, shape and depths of the sedimentary basin where the Mensabé and Salados rivers hydrogeological sub-basin is located. The model shows the connections between tectonics and the sedimentary basin, suggesting the probable areas for aquifers, the relations between them, their zone of recharge and discharge, and the probable zone of pollution. The inferred faults in the model may be the main recharge and discharge conduits for the groundwater and anthropogenic pollution. The geological and geometric characteristics shown in the 3D model are fundamental data for further hydrogeological and geophysical studies such as the location for future drinking water wells.
3-D wavelet compression and progressive inverse wavelet synthesis rendering of concentric mosaic.
Luo, Lin; Wu, Yunnan; Li, Jin; Zhang, Ya-Qin
2002-01-01
Using an array of photo shots, the concentric mosaic offers a quick way to capture and model a realistic three-dimensional (3-D) environment. We compress the concentric mosaic image array with a 3-D wavelet transform and coding scheme. Our compression algorithm and bitstream syntax are designed to ensure that a local view rendering of the environment requires only a partial bitstream, thereby eliminating the need to decompress the entire compressed bitstream before rendering. By exploiting the ladder-like structure of the wavelet lifting scheme, the progressive inverse wavelet synthesis (PIWS) algorithm is proposed to maximally reduce the computational cost of selective data accesses on such wavelet compressed datasets. Experimental results show that the 3-D wavelet coder achieves high-compression performance. With the PIWS algorithm, a 3-D environment can be rendered in real time from a compressed dataset.
3D LBFGS inversion of controlled source extremely low frequency electromagnetic data
NASA Astrophysics Data System (ADS)
Cao, Meng; Tan, Han-Dong; Wang, Kun-Peng
2016-12-01
The controlled source extremely low frequency (CSELF) electromagnetic method is characterized by extremely long and powerful sources and a huge measurement range. Its electromagnetic field can therefore be affected by the ionosphere and displacement current. Research on 3D forward modeling and inversion of CSELF electromagnetic data is currently in its infancy. This paper makes exploratory attempts to firstly calculate the 1D extremely low frequency electromagnetic field under ionosphere-air-earth coupling circumstances, and secondly analyze the propagation characteristics of the background electromagnetic field. The 3D staggered-grid finite difference scheme for solving for the secondary electric field is adopted and incorporated with the 1D modeling algorithm to complete 3D forward modeling. Considering that surveys can be carried out in the near field and transition zone for lower frequencies, the 3D Limited-memory Broyden-Fletcher-Goldfarb-Shanno (LBFGS) inversion of CSELF electromagnetic data is presented (in which the sources, or primary fields, are included), with the aim of directly inverting the impedance data, regardless of where it is acquired. Derivation of the objective functional gradient is the core component in the inversion. Synthetic tests indicate that the well-chosen approximation to the Hessian can significantly speed up the inversion. The model responses corresponding to the coexistence of conductive and resistive blocks show that the off-diagonal components of tensor impedance are much more sensitive to the resistivity variation than the diagonal components. In comparison with conventional scalar inversion, tensor inversion is superior in the recoveries of electric anomalies and background resistivity.
NASA Astrophysics Data System (ADS)
Rosas-Carbajal, M.; Linde, N.; Peacock, J.; Zyserman, F. I.; Kalscheuer, T.; Thiel, S.
2015-12-01
Surface-based monitoring of mass transfer caused by injections and extractions in deep boreholes is crucial to maximize oil, gas and geothermal production. Inductive electromagnetic methods, such as magnetotellurics, are appealing for these applications due to their large penetration depths and sensitivity to changes in fluid conductivity and fracture connectivity. In this work, we propose a 3-D Markov chain Monte Carlo inversion of time-lapse magnetotelluric data to image mass transfer following a saline fluid injection. The inversion estimates the posterior probability density function of the resulting plume, and thereby quantifies model uncertainty. To decrease computation times, we base the parametrization on a reduced Legendre moment decomposition of the plume. A synthetic test shows that our methodology is effective when the electrical resistivity structure prior to the injection is well known. The centre of mass and spread of the plume are well retrieved. We then apply our inversion strategy to an injection experiment in an enhanced geothermal system at Paralana, South Australia, and compare it to a 3-D deterministic time-lapse inversion. The latter retrieves resistivity changes that are more shallow than the actual injection interval, whereas the probabilistic inversion retrieves plumes that are located at the correct depths and oriented in a preferential north-south direction. To explain the time-lapse data, the inversion requires unrealistically large resistivity changes with respect to the base model. We suggest that this is partly explained by unaccounted subsurface heterogeneities in the base model from which time-lapse changes are inferred.
3-D inversion of gravity data in spherical coordinates with application to the GRAIL data
NASA Astrophysics Data System (ADS)
Liang, Qing; Chen, Chao; Li, Yaoguo
2014-06-01
Three-dimensional (3-D) inversion of gravity data has been widely used to reconstruct the density distributions of ore bodies, basins, crust, lithosphere, and upper mantle. For global model of 3-D density structures of planetary interior, such as the Earth, the Moon, or Mars, it is necessary to use an inversion algorithm that operates in the spherical coordinates. We develop a 3-D inversion algorithm formulated with specially designed model objective function and radial weighting function in the spherical coordinates. We present regional and global synthetic examples to illustrate the capability of the algorithm. The inverted results show density distribution features consistent with the true models. We also apply the algorithm to a set of lunar Bouguer gravity anomaly derived from the Gravity Recovery and Interior Laboratory (GRAIL) gravity field and obtain a lunar 3-D density distribution. High-density anomalies are clearly identified underlying lunar basins, a wide region of the lateral density heterogeneities that exist beneath the South Pole-Aitken basin are found, and low-density anomalies are distributed beneath the Feldspathic Highlands Terrane on the lunar far-side. The consistency of these results with those obtained independently from other existing methods verifies the newly developed algorithm.
Anisotropic 3D inversion of towed streamer EM data from the Troll West oil province (Invited)
NASA Astrophysics Data System (ADS)
Mattsson, J.; Midgley, J.; Zhdanov, M. S.; ENDO, M.
2013-12-01
Obviating the need for ocean bottom receivers, the towed streamer EM system enables CSEM data to be acquired simultaneously with seismic over very large areas in frontier and mature basins for higher production rates and more cost effective than conventional marine CSEM. The towed streamer EM data are currently processed and delivered as a spectrum of frequency-domain responses. We apply a 3D anisotropic inversion methodology for towed streamer EM data that includes a moving sensitivity domain. Our implementation is based on the 3D contraction integral equation method for computing the EM responses and Fréchet derivatives, and uses the re-weighted regularized conjugate gradient method for minimizing the objective functional with focusing regularization. We present an actual case study for the 3D anisotropic inversion of towed streamer EM data from the Troll West oil province in the North Sea, and demonstrate our ability to image the Troll West Oil and Gas Provinces. We conclude that 3D anisotropic inversion of the data from the current generation of towed streamer EM system can adequately recover both the vertical and horizontal resistivities in anisotropic hydrocarbon-bearing formations.
3D gravity inversion and uncertainty assessment of basement relief via Particle Swarm Optimization
NASA Astrophysics Data System (ADS)
Pallero, J. L. G.; Fernández-Martínez, J. L.; Bonvalot, S.; Fudym, O.
2017-04-01
Nonlinear gravity inversion in sedimentary basins is a classical problem in applied geophysics. Although a 2D approximation is widely used, 3D models have been also proposed to better take into account the basin geometry. A common nonlinear approach to this 3D problem consists in modeling the basin as a set of right rectangular prisms with prescribed density contrast, whose depths are the unknowns. Then, the problem is iteratively solved via local optimization techniques from an initial model computed using some simplifications or being estimated using prior geophysical models. Nevertheless, this kind of approach is highly dependent on the prior information that is used, and lacks from a correct solution appraisal (nonlinear uncertainty analysis). In this paper, we use the family of global Particle Swarm Optimization (PSO) optimizers for the 3D gravity inversion and model appraisal of the solution that is adopted for basement relief estimation in sedimentary basins. Synthetic and real cases are illustrated, showing that robust results are obtained. Therefore, PSO seems to be a very good alternative for 3D gravity inversion and uncertainty assessment of basement relief when used in a sampling while optimizing approach. That way important geological questions can be answered probabilistically in order to perform risk assessment in the decisions that are made.
Fast 3D inversion of airborne gravity-gradiometry data using Lanczos bidiagonalization method
NASA Astrophysics Data System (ADS)
Meng, Zhaohai; Li, Fengting; Zhang, Dailei; Xu, Xuechun; Huang, Danian
2016-09-01
We developed a new fast inversion method for to process and interpret airborne gravity gradiometry data, which was based on Lanczos bidiagonalization algorithm. Here, we describe the application of this new 3D gravity gradiometry inversion method to recover a subsurface density distribution model from the airborne measured gravity gradiometry anomalies. For this purpose, the survey area is divided into a large number of rectangular cells with each cell possessing a constant unknown density. It is well known that the solution of large linear gravity gradiometry is an ill-posed problem since using the smoothest inversion method is considerably time consuming. We demonstrate that the Lanczos bidiagonalization method can be an appropriate algorithm to solve a Tikhonov solver time cost function for resolving the large equations within a short time. Lanczos bidiagonalization is designed to make the very large gravity gradiometry forward modeling matrices to become low-rank, which will considerably reduce the running time of the inversion method. We also use a weighted generalized cross validation method to choose the appropriate Tikhonov parameter to improve inversion results. The inversion incorporates a model norm that allows us to attain the smoothing and depth of the solution; in addition, the model norm counteracts the natural decay of the kernels, which concentrate at shallow depths. The method is applied on noise-contaminated synthetic gravity gradiometry data to demonstrate its suitability for large 3D gravity gradiometry data inversion. The airborne gravity gradiometry data from the Vinton Salt Dome, USE, were considered as a case study. The validity of the new method on real data is discussed with reference to the Vinton Dome inversion result. The intermediate density values in the constructed model coincide well with previous results and geological information. This demonstrates the validity of the gravity gradiometry inversion method.
Fast 3D inversion of gravity data using solution space priorconditioned lanczos bidiagonalization
NASA Astrophysics Data System (ADS)
Rezaie, Mohammad; Moradzadeh, Ali; Kalateh, Ali Nejati
2017-01-01
Inversion of gravity data is one of the most important steps in the quantitative interpretation of practical data. Inversion is a mathematical technique that automatically constructs a subsurface geophysical model from measured data, incorporating some priori information. Inversion of gravity data is time consuming because of increase in data and model parameters. Some efforts have been made to deal with this problem, one of them is using fast algorithms for solving system of equations in inverse problem. Lanczos bidiagonalization method is a fast algorithm that works based on Krylov subspace iterations and projection method, but cannot always provide a good basis for a projection method. So in this study, we combined the Krylov method with a regularization method applied to the low-dimensional projected problem. To achieve the goal, the orthonormal basis vectors of the discrete cosine transform (DCT) were used to build the low-dimensional subspace. The forward operator matrix replaced with a matrix of lower dimension, thus, the required memory and running time of the inverse modeling is decreased by using the proposed algorithm. It is shown that this algorithm can be appropriate to solve a Tikhonov cost function for inversion of gravity data. The proposed method has been applied on a noise-corrupted synthetic data and field gravity data (Mobrun gravity data) to demonstrate its reliability for three dimensional (3D) gravity inversion. The obtained results of 3D inversion both synthetic and field gravity data (Mobrun gravity data) indicate the proposed inversion algorithm could produce density models consistent with true structures.
NASA Astrophysics Data System (ADS)
Beka, Thomas I.; Smirnov, Maxim; Birkelund, Yngve; Senger, Kim; Bergh, Steffen G.
2016-08-01
Broadband (0.001-1000 s) magnetotelluric (MT) data along a crooked profile collected to investigate the geothermal potential on Spitsbergen could not be fully explained by two-dimensional (2D) models; hence we interpret the data with three-dimensional (3D) inversion herein. To better accommodate 3D features and nearby off profile resistivity structures, the full MT impedance tensor data together with the tipper were inverted. As a model control, a detailed bathymetry is systematically incorporated in the inversion. Our results from testing different inversion settings emphasised that appropriately choosing and tuning the starting model, data error floor and the model regularization together are crucial to obtain optimum benefit from MT field data. Through the 3D inversion, we reproduced out of quadrant impedance components and obtained an overall satisfactory data fit (RMS = 1.05). The final 3D resistivity model displays a complex geology of the near surface region (< 1.5 km), which suggests fractures, localized and regional fault systems and igneous intrusions in the Mesozoic platform cover deposits. The Billefjorden fault zone is revealed as a consistent and deep rooted (> 2 km) conductive anomaly, confirming the regional nature of the fault. The fault zone is positioned between two uplifted basement blocks (> 1000 Ωm) of presumably pre-Devonian (Caledonian) metamorphic rocks, and the fault may have been responsible for deformation in the overlying Paleozoic-Mesozoic unit. Upper crustal conductive anomalies (< 10 Ωm) below the Paleozoic-Mesozoic succession in the western part of the 3D model are interpreted as part of a Devonian basin fill. These conductors are laterally and vertically bounded by resistive rocks, suggesting a conducive environment for deep geothermal heat storage. Having this scenario in an area of a known high heat-flow, deep faults and a thinned lithosphere makes the hypothesis on finding a technologically exploitable geothermal resource
Large scale 3-D modeling by integration of resistivity models and borehole data through inversion
NASA Astrophysics Data System (ADS)
Foged, N.; Marker, P. A.; Christansen, A. V.; Bauer-Gottwein, P.; Jørgensen, F.; Høyer, A.-S.; Auken, E.
2014-02-01
We present an automatic method for parameterization of a 3-D model of the subsurface, integrating lithological information from boreholes with resistivity models through an inverse optimization, with the objective of further detailing for geological models or as direct input to groundwater models. The parameter of interest is the clay fraction, expressed as the relative length of clay-units in a depth interval. The clay fraction is obtained from lithological logs and the clay fraction from the resistivity is obtained by establishing a simple petrophysical relationship, a translator function, between resistivity and the clay fraction. Through inversion we use the lithological data and the resistivity data to determine the optimum spatially distributed translator function. Applying the translator function we get a 3-D clay fraction model, which holds information from the resistivity dataset and the borehole dataset in one variable. Finally, we use k means clustering to generate a 3-D model of the subsurface structures. We apply the concept to the Norsminde survey in Denmark integrating approximately 700 boreholes and more than 100 000 resistivity models from an airborne survey in the parameterization of the 3-D model covering 156 km2. The final five-cluster 3-D model differentiates between clay materials and different high resistive materials from information held in resistivity model and borehole observations respectively.
Large-scale 3-D modeling by integration of resistivity models and borehole data through inversion
NASA Astrophysics Data System (ADS)
Foged, N.; Marker, P. A.; Christansen, A. V.; Bauer-Gottwein, P.; Jørgensen, F.; Høyer, A.-S.; Auken, E.
2014-11-01
We present an automatic method for parameterization of a 3-D model of the subsurface, integrating lithological information from boreholes with resistivity models through an inverse optimization, with the objective of further detailing of geological models, or as direct input into groundwater models. The parameter of interest is the clay fraction, expressed as the relative length of clay units in a depth interval. The clay fraction is obtained from lithological logs and the clay fraction from the resistivity is obtained by establishing a simple petrophysical relationship, a translator function, between resistivity and the clay fraction. Through inversion we use the lithological data and the resistivity data to determine the optimum spatially distributed translator function. Applying the translator function we get a 3-D clay fraction model, which holds information from the resistivity data set and the borehole data set in one variable. Finally, we use k-means clustering to generate a 3-D model of the subsurface structures. We apply the procedure to the Norsminde survey in Denmark, integrating approximately 700 boreholes and more than 100 000 resistivity models from an airborne survey in the parameterization of the 3-D model covering 156 km2. The final five-cluster 3-D model differentiates between clay materials and different high-resistivity materials from information held in the resistivity model and borehole observations, respectively.
NASA Astrophysics Data System (ADS)
Klibanov, Michael V.; Romanov, Vladimir G.
2016-01-01
The 3D inverse scattering problem of the reconstruction of the unknown dielectric permittivity in the generalized Helmholtz equation is considered. Applications are in imaging of nanostructures and biological cells. The main difference with the conventional inverse scattering problems is that only the modulus of the scattering wave field is measured. The phase is not measured. The initializing wave field is the incident plane wave. On the other hand, in the previous recent works of the authors about the ‘phaseless topic’ the case of the point source was considered (Klibanov and Romanov 2015 J. Inverse Ill-Posed Problem 23 415-28 J. Inverse Ill-Posed Problem 23 187-93). Two reconstruction procedures are developed.
Application of 3D variation-density interface inversion of gravity anomalies in South China Sea
NASA Astrophysics Data System (ADS)
Li, Shuling; Meng, Xiaohong
2017-04-01
The South China Sea (SCS) is a marginal basin with extremely complicated crustal structure and whose evolutional history is associated with continental rifting and seafloor spreading. The gravity data are among the most important data sets for studying deep crustal structures and the tectonic evolution. Density interface inversion by gravity anomalies can effectively estimate the depth of Moho interface. However, the Moho interface inversion in SCS are facing challenges due to the density contract of crust-mantle vary in three dimensions, which are associated with the complicated crustal structure (co-existing oceanic crust, continental crust and transitional crust). The regular inversion methods always assume the density contract on both sides of the interface would be constant, which is quite unrealistic since actual strata densities vary both vertically and laterally. To meet the challenges of 3D variation of density in SCS, we present an improved 3D variation-density interface inversion of gravity anomalies based on Parker-Oldenburg method. We first construct two variation density models with exponential density-depth relationships, which expressed the variation of stratum density depending on the depth in oceanic and continental crust respectively. Meanwhile, to minimize multiple solutions for potential field inversion, we collect deep seismic sounding data and employ the gravity inversion by joint using seismic data to be constraint for depth of Moho. Finally, we have estimated the depth of Moho interface which infers the tectonic significance in SCS. The inversion results agree well with seismic data in SCS show this approach is more effective and precise to quantitative estimate the depth of interface. Keywords: South China Sea; Gravity anomalies; Density interface inversion;
Inverse compositional estimation of 3D pose and lighting in dynamic scenes.
Xu, Yilei; Roy-Chowdhury, Amit
2008-07-01
In this paper, we show how to estimate, accurately and efficiently, the 3D motion of a rigid object and time-varying lighting in a dynamic scene. This is achieved in an inverse compositional tracking framework with a novel warping function that involves a 2D --> 3D --> 2D transformation. This also allows us to extend traditional two frame inverse compositional tracking to a sequence of frames, leading to even higher computational savings. We prove the theoretical convergence of this method and show that it leads to significant reduction in computational burden. Experimental analysis on multiple video sequences shows impressive speed-up over existing methods while retaining a high level of accuracy.
3D Motion Planning Algorithms for Steerable Needles Using Inverse Kinematics
Duindam, Vincent; Xu, Jijie; Alterovitz, Ron; Sastry, Shankar; Goldberg, Ken
2010-01-01
Steerable needles can be used in medical applications to reach targets behind sensitive or impenetrable areas. The kinematics of a steerable needle are nonholonomic and, in 2D, equivalent to a Dubins car with constant radius of curvature. In 3D, the needle can be interpreted as an airplane with constant speed and pitch rate, zero yaw, and controllable roll angle. We present a constant-time motion planning algorithm for steerable needles based on explicit geometric inverse kinematics similar to the classic Paden-Kahan subproblems. Reachability and path competitivity are analyzed using analytic comparisons with shortest path solutions for the Dubins car (for 2D) and numerical simulations (for 3D). We also present an algorithm for local path adaptation using null-space results from redundant manipulator theory. Finally, we discuss several ways to use and extend the inverse kinematics solution to generate needle paths that avoid obstacles. PMID:21359051
NASA Astrophysics Data System (ADS)
Bell, R. E.; Morgan, J. V.; Warner, M.
2013-12-01
Our understanding of subduction margin seismogenesis has been revolutionised in the last couple of decades with the discovery that the size of the seismogenic zone may not be controlled simply by temperature and a broad spectrum of seismic behaviour exists from stick-slip to stable sliding. Laboratory and numerical experiments suggest that physical properties, particularly fluid pressure may play an important role in controlling the seismic behaviour of subduction margins. Although drilling can provide information on physical properties along subduction thrust faults at point locations at relatively shallow depths, correlations between physical properties and seismic velocity using rock physics relationships are required to resolve physical properties along the margin and down-dip. Therefore, high resolution seismic velocity models are key to recovering physical property information at subduction plate boundaries away from drill sites. 3D Full waveform inversion (FWI) is a technique pioneered by the oil industry to obtain high-resolution high-fidelity models of physical properties in the sub-surface. 3D FWI involves the inversion of low-frequency (>2 to <7 Hz), early arriving (principally transmitted) seismic data, to recover the macro (intermediate to long-wavelength) velocity structure. Although 2D FWI has been used to improve velocity models of subduction plate boundaries before, 3D FWI has not yet been attempted. 3D inversions have superior convergence and accuracy, as they sample the subsurface with multi-azimuth multiply-crossing wavefields. In this contribution we perform a suite of synthetic tests to investigate if 3D FWI could be used to better resolve physical property information along subduction margin plate boundaries using conventionally collected 3D seismic data. We base our analysis on the Muroto Basin area of the Nankai margin and investigate if the acquisition parameters and geometry of the subduction margin render 3D seismic data collected across
3-D Sound Propagation and Acoustic Inversions in Shallow Water Oceans
2011-09-01
method is used to study canonical environmental models of shelfbreak front systems and nonlinear internal wave ducts. The WHOI 3D Parabolic-Equation...localization methods with normal mode theory have been established for localizing low frequency, broadband signals in a shallow water environment. Gauss ...approach for low-frequency broadband sound source localization in a shallow-water ocean is established. Gauss -Markov inverse theory is used in both
Uniqueness of a 3-D coefficient inverse scattering problem without the phase information
NASA Astrophysics Data System (ADS)
Klibanov, Michael V.; Romanov, Vladimir G.
2017-09-01
We use a new method to prove the uniqueness theorem for a coefficient inverse scattering problem without the phase information for the 3-D Helmholtz equation. We consider the case when only the modulus of the scattered wave field is measured and the phase is not measured. The spatially distributed refractive index is the subject of interest in this problem. Applications of this problem are in imaging of nanostructures and biological cells.
Sensitivity study of 3-D modeling for multi-D inversion of surface NMR
NASA Astrophysics Data System (ADS)
Warsa, Grandis, Hendra
2012-06-01
Geophysical field method of surface nuclear magnetic resonance (SNMR) allows a direct determination of hydrogeological parameters of the subsurface. The amplitude of the SNMR signal is directly linked to the amount of mobile water. The relaxation behaviour of the signal correlates with pore sizes and hydraulic conductivities of an aquifer. For improving capability and reliability of SNMR method we have presented a forward modeling scheme of 3-D water content and decay time structures that can be used for multi-D interpretation. Currently SNMR is carried out mainly with a 1-D working scheme using coinciding loops. For each sounding point using a coincident circular loop antenna, the amplitudes and decay times of the SNMR signal are the product of a three dimensional distribution of the water content and decay time in the subsurface and their sensitivity to the receiver. The antenna is moved at the surface and the SNMR relaxation signal are plotted as a function of the pulse moment and sounding point. The errors might be very large by neglecting the 2-D or even 3-D geometry of the structures which have to be considered in the analysis and inversion in the future. The results show that the 3-D modeling is reliable and flexible to be integrated into the 2-D/3-D inversion scheme for inverting surface NMR data to recover a multi-D distribution of water content and decay time of an aquifer.
Comparison of Compressed Sensing Algorithms for Inversion of 3-D Electrical Resistivity Tomography.
NASA Astrophysics Data System (ADS)
Peddinti, S. R.; Ranjan, S.; Kbvn, D. P.
2016-12-01
Image reconstruction algorithms derived from electrical resistivity tomography (ERT) are highly non-linear, sparse, and ill-posed. The inverse problem is much severe, when dealing with 3-D datasets that result in large sized matrices. Conventional gradient based techniques using L2 norm minimization with some sort of regularization can impose smoothness constraint on the solution. Compressed sensing (CS) is relatively new technique that takes the advantage of inherent sparsity in parameter space in one or the other form. If favorable conditions are met, CS was proven to be an efficient image reconstruction technique that uses limited observations without losing edge sharpness. This paper deals with the development of an open source 3-D resistivity inversion tool using CS framework. The forward model was adopted from RESINVM3D (Pidlisecky et al., 2007) with CS as the inverse code. Discrete cosine transformation (DCT) function was used to induce model sparsity in orthogonal form. Two CS based algorithms viz., interior point method and two-step IST were evaluated on a synthetic layered model with surface electrode observations. The algorithms were tested (in terms of quality and convergence) under varying degrees of parameter heterogeneity, model refinement, and reduced observation data space. In comparison to conventional gradient algorithms, CS was proven to effectively reconstruct the sub-surface image with less computational cost. This was observed by a general increase in NRMSE from 0.5 in 10 iterations using gradient algorithm to 0.8 in 5 iterations using CS algorithms.
Application of 3D variation-density interface inversion of gravity anomalies in South China Sea
NASA Astrophysics Data System (ADS)
LI, S.; Meng, X.; HU, Y.; Zhang, S.
2016-12-01
The South China Sea (SCS) is a marginal basin with extremely complicated crustal structure and whose evolutional history is associated with continental rifting and seafloor spreading. The gravity data are among the most important data sets for studying deep crustal structures and the tectonic evolution. Density interface inversion by gravity anomalies can effectively estimate the depth of Moho interface. However, the Moho interface inversion in SCS are facing challenges due to the density contract of crust-mantle vary in three dimensions, which are associated with the complicated crustal structure (co-existing oceanic crust, continental crust and transitional crust). The regular inversion methods always assume the density contract on both sides of the interface would be constant, which is quite unrealistic since actual strata densities vary both vertically and laterally. To meet the challenges of 3D variation of density in SCS, we present an improved 3D variation-density interface inversion of gravity anomalies based on Parker-Oldenburg method. We first construct two variation density models with exponential density-depth relationships, which expressed the variation of stratum density depending on the depth in oceanic and continental crust respectively. Meanwhile, to minimize multiple solutions for potential field inversion, we collect deep seismic sounding data and employ the gravity inversion by joint using seismic data to be constraint for depth of Moho. Finally, we have estimated the depth of Moho interface which infers the tectonic significance in SCS. The inversion results agree well with seismic data in SCS show this approach is more effective and precise to quantitative estimate the depth of interface.
NASA Astrophysics Data System (ADS)
Liu, B.; Li, S. C.; Nie, L. C.; Wang, J.; L, X.; Zhang, Q. S.
2012-12-01
Traditional inversion method is the most commonly used procedure for three-dimensional (3D) resistivity inversion, which usually takes the linearization of the problem and accomplish it by iterations. However, its accuracy is often dependent on the initial model, which can make the inversion trapped in local optima, even cause a bad result. Non-linear method is a feasible way to eliminate the dependence on the initial model. However, for large problems such as 3D resistivity inversion with inversion parameters exceeding a thousand, main challenges of non-linear method are premature and quite low search efficiency. To deal with these problems, we present an improved Genetic Algorithm (GA) method. In the improved GA method, smooth constraint and inequality constraint are both applied on the object function, by which the degree of non-uniqueness and ill-conditioning is decreased. Some measures are adopted from others by reference to maintain the diversity and stability of GA, e.g. real-coded method, and the adaptive adjustment of crossover and mutation probabilities. Then a generation method of approximately uniform initial population is proposed in this paper, with which uniformly distributed initial generation can be produced and the dependence on initial model can be eliminated. Further, a mutation direction control method is presented based on the joint algorithm, in which the linearization method is embedded in GA. The update vector produced by linearization method is used as mutation increment to maintain a better search direction compared with the traditional GA with non-controlled mutation operation. By this method, the mutation direction is optimized and the search efficiency is improved greatly. The performance of improved GA is evaluated by comparing with traditional inversion results in synthetic example or with drilling columnar sections in practical example. The synthetic and practical examples illustrate that with the improved GA method we can eliminate
Kılıç, Emre Eibert, Thomas F.
2015-05-01
An approach combining boundary integral and finite element methods is introduced for the solution of three-dimensional inverse electromagnetic medium scattering problems. Based on the equivalence principle, unknown equivalent electric and magnetic surface current densities on a closed surface are utilized to decompose the inverse medium problem into two parts: a linear radiation problem and a nonlinear cavity problem. The first problem is formulated by a boundary integral equation, the computational burden of which is reduced by employing the multilevel fast multipole method (MLFMM). Reconstructed Cauchy data on the surface allows the utilization of the Lorentz reciprocity and the Poynting's theorems. Exploiting these theorems, the noise level and an initial guess are estimated for the cavity problem. Moreover, it is possible to determine whether the material is lossy or not. In the second problem, the estimated surface currents form inhomogeneous boundary conditions of the cavity problem. The cavity problem is formulated by the finite element technique and solved iteratively by the Gauss–Newton method to reconstruct the properties of the object. Regularization for both the first and the second problems is achieved by a Krylov subspace method. The proposed method is tested against both synthetic and experimental data and promising reconstruction results are obtained.
NASA Astrophysics Data System (ADS)
Cubuk-Sabuncu, Yesim; Taymaz, Tuncay; Fichtner, Andreas
2016-04-01
We present a 3D radially anisotropic velocity model of the crust and uppermost mantle structure beneath the Sea of Marmara and surroundings based on the full waveform inversion method. The intense seismic activity and crustal deformation are observed in the Northwest Turkey due to transition tectonics between the strike-slip North Anatolian Fault (NAF) and the extensional Aegean region. We have selected and simulated complete waveforms of 62 earthquakes (Mw > 4.0) occurred during 2007-2015, and recorded at (Δ < 10°) distances. Three component earthquake data is obtained from broadband seismic stations of Kandilli Observatory and Earthquake Research Center (KOERI, Turkey), Hellenic Unified Seismic Network (HUSN, Greece) and Earthquake Research Center of Turkey (AFAD-DAD). The spectral-element solver of the wave equation, SES3D algorithm, is used to simulate seismic wave propagation in 3D spherical coordinates (Fichtner, 2009). The Large Scale Seismic Inversion Framework (LASIF) workflow tool is also used to perform full seismic waveform inversion (Krischer et al., 2015). The initial 3D Earth model is implemented from the multi-scale seismic tomography study of Fichtner et al. (2013). Discrepancies between the observed and simulated synthetic waveforms are determined using the time-frequency misfits which allows a separation between phase and amplitude information (Fichtner et al., 2008). The conjugate gradient optimization method is used to iteratively update the initial Earth model when minimizing the misfit. The inversion is terminated after 19 iterations since no further advances are observed in updated models. Our analysis revealed shear wave velocity variations of the shallow and deeper crustal structure beneath western Turkey down to depths of ~35-40 km. Low shear wave velocity anomalies are observed in the upper and mid crustal depths beneath major fault zones located in the study region. Low velocity zones also tend to mark the outline of young volcanic
The multi-scale 3D-1D compatibility scoring for inverse protein folding problem
Oniuka, Kentaro; Asai, Kiyoshi
1994-12-31
The applicability of the Multi-Scale Structure Description (MSSD) scheme to the inverse-folding problems was investigated. An MSSD represents a 3D protein structure with multiple symbolic sequences, where fine structures are represented with the sequence at low levels, the middle scale structural motifs at middle levels, and global topology at high levels. Each symbol in the symbolic sequence denotes a type of local structure of the level scale. The structure fragments are classified at each scale level respectively according to the shape and the environment around the fragments: how the structure is exposed to the solvent or buried in the molecule. I modeled the propensity of an amino-acid sequence to the structure fragment type (i.e., primary constraint) at each scale level. The local propensity is, therefore, modeled at small scale (low) levels, while the global propensity modeled at large scale (high) levels. Thus, superposing all the primary constraints, a 3D protein structure yields an amino-acid sequence profile. Evaluating the fit of an amino acid sequence to the profile derived from the known 3D protein structure, we can identify which 3D structure the given amino-acid sequence would fold into. I checked whether a sequence identifies its own structure over two hundred protein sequences. In many cases, an amino acid sequence identified its own 3D protein structure.
3D inversion of land-based CSEM data from the Ketzin CO2 storage formation
NASA Astrophysics Data System (ADS)
Grayver, Alexander; Streich, Rita; Ritter, Oliver
2013-04-01
We present 3D inversion of land controlled-source electromagnetic (CSEM) data collected across the CO2 storage test site at Ketzin, Germany. The CSEM data were generated by injecting currents into the earth at eight locations using a newly developed transmitter equipped with three grounded electrodes. Electric and magnetic field responses were recorded by 39 receivers along a line approximately perpendicular to the main geological trend. The survey aimed at imaging large-scale resistivity structure beyond the near-well region monitored by higher-resolution electrical techniques. Infrastructure present in the survey area, such as pipelines with impressed-current cathodic protection systems, power lines, and wind power plants cause strong noise in the data. The noise is effectively suppressed by adopting statistically robust processing techniques known from passive magnetotellurics. A newly developed Gauss-Newton type parallel distributed inversion scheme, which is based on a direct forward solver and explicitly calculates the full sensitivity matrix, is applied to recover subsurface conductivity images. As 3D inversion is demanding on computer time and memory, we run inversions on parallel distributed machines. We achieve good scalability by distributing computations and memory uniformly among the processes involved. We carry out cumulative sensitivity and resolution analyses for the sparse CSEM acquisition geometry. These studies indicate reasonable spatial coverage along the main survey line. Synthetic studies calculated for the real survey layout and representative conductivity models indicate that the magnetic field components are practically insensitive to resistive structures, whereas the electric field components resolve resistors and conductors similarly well. Because the magnetic field contributes little subsurface information, we concentrate on inverting the electric field, which is also more computer-efficient than inverting all components. We test
Simultaneous elastic parameter inversion in 2-D/3-D TTI medium combined later arrival times
NASA Astrophysics Data System (ADS)
Bai, Chao-ying; Wang, Tao; Yang, Shang-bei; Li, Xing-wang; Huang, Guo-jiao
2016-04-01
Traditional traveltime inversion for anisotropic medium is, in general, based on a "weak" assumption in the anisotropic property, which simplifies both the forward part (ray tracing is performed once only) and the inversion part (a linear inversion solver is possible). But for some real applications, a general (both "weak" and "strong") anisotropic medium should be considered. In such cases, one has to develop a ray tracing algorithm to handle with the general (including "strong") anisotropic medium and also to design a non-linear inversion solver for later tomography. Meanwhile, it is constructive to investigate how much the tomographic resolution can be improved by introducing the later arrivals. For this motivation, we incorporated our newly developed ray tracing algorithm (multistage irregular shortest-path method) for general anisotropic media with a non-linear inversion solver (a damped minimum norm, constrained least squares problem with a conjugate gradient approach) to formulate a non-linear inversion solver for anisotropic medium. This anisotropic traveltime inversion procedure is able to combine the later (reflected) arrival times. Both 2-D/3-D synthetic inversion experiments and comparison tests show that (1) the proposed anisotropic traveltime inversion scheme is able to recover the high contrast anomalies and (2) it is possible to improve the tomographic resolution by introducing the later (reflected) arrivals, but not as expected in the isotropic medium, because the different velocity (qP, qSV and qSH) sensitivities (or derivatives) respective to the different elastic parameters are not the same but are also dependent on the inclination angle.
Integrated gravity and gravity gradient 3D inversion using the non-linear conjugate gradient
NASA Astrophysics Data System (ADS)
Qin, Pengbo; Huang, Danian; Yuan, Yuan; Geng, Meixia; Liu, Jie
2016-03-01
Gravity data, which are critical in mineral, oil, and gas exploration, are obtained from the vertical component of the gravity field, while gravity gradient data are measured from changes in the gravity field in three directions. However, few studies have sought to improve exploration techniques by integrating gravity and gravity gradient data using inversion methods. In this study, we developed a new method to integrate gravity and gravity gradient data in a 3D density inversion using the non-linear conjugate gradient (NLCG) method and the minimum gradient support (MGS) functional to regularize the 3D inverse problem and to obtain a clear and accurate image of the anomalous body. The NLCG algorithm, which is suitable for solving large-scale nonlinear optimization problems and requires no memory storage, was compared to the Broyden-Fletcher-Goldfarb-Shanno (BFGS) quasi-Newton algorithm and the results indicated that the convergence rate of NLCG is slower, but that the storage requirement and computation time is lower. To counteract the decay in kernel function, we introduced a depth weighting function for anomalous bodies at the same depth, with information about anomalous body depth obtained from well log and seismic exploration data. For anomalous bodies at different depths, we introduced a spatial gradient weighting function to incorporate additional information obtained in the inversion. We concluded that the spatial gradient weighting function enhanced the spatial resolution of the recovered model. Furthermore, our results showed that including multiple components for inversion increased the resolution of the recovered model. We validated our model by applying our inversion method to survey data from Vinton salt dome, Louisiana, USA. The results showed good agreement with known geologic information; thus confirming the accuracy of this approach.
3D Inversion of complex resistivity data: Case study on Mineral Exploration Site.
NASA Astrophysics Data System (ADS)
Son, Jeong-Sul; Kim, Jung-ho; Park, Sam-gyu; Park, My-Kyung
2016-04-01
Complex resistivity (CR) method is a frequency domain induced polarization (IP) method. It is also known as Spectral IP (SIP) method, if wider frequencies are used in data acquisition and interpretation. Although it takes more times than conventional time domain IP method, its data quality is more stable because its data acquisition which measures amplitude and phase is done when the source current is being injected. Our research group has been studying the modeling and inversion algorithms of complex resistivity (CR) method since several years ago and recently applied developed algorithms to various real field application. Due to tough terrain in our country, Profile survey and 2D interpretation were generally used. But to get more precise interpretation, three dimensional modeling and inversion algorithm is required. We developed three dimensional inversion algorithm for this purpose. In the inversion, we adopt the method of adaptive lagraingian multiplier which is automatically set based on the size of error misfit and model regularization norm. It was applied on the real data acquired for mineral exploration sites. CR data was acquired with the Zeta system, manufactured by Zonge Co. In the inversion, only the lower frequency data is used considering its quality and developed 3D inversion algorithm was applied to the acquired data set. Its results were compared to those of time domain IP data conducted at the same site. Resistivity image sections of CR and conventional resistivity method were almost identical. Phase anomalies were well matched with chargeability anomalies and the mining history of the test site. Each anomalies were well discriminated in 3D interpretation than those of 2D. From those experiments, we know that CR method was very effective for the mineral exploration.
Rosas-Carbajal, Marina; Linde, Nicolas; Peacock, Jared R.; Zyserman, F. I.; Kalscheuer, Thomas; Thiel, Stephan
2015-01-01
Surface-based monitoring of mass transfer caused by injections and extractions in deep boreholes is crucial to maximize oil, gas and geothermal production. Inductive electromagnetic methods, such as magnetotellurics, are appealing for these applications due to their large penetration depths and sensitivity to changes in fluid conductivity and fracture connectivity. In this work, we propose a 3-D Markov chain Monte Carlo inversion of time-lapse magnetotelluric data to image mass transfer following a saline fluid injection. The inversion estimates the posterior probability density function of the resulting plume, and thereby quantifies model uncertainty. To decrease computation times, we base the parametrization on a reduced Legendre moment decomposition of the plume. A synthetic test shows that our methodology is effective when the electrical resistivity structure prior to the injection is well known. The centre of mass and spread of the plume are well retrieved.We then apply our inversion strategy to an injection experiment in an enhanced geothermal system at Paralana, South Australia, and compare it to a 3-D deterministic time-lapse inversion. The latter retrieves resistivity changes that are more shallow than the actual injection interval, whereas the probabilistic inversion retrieves plumes that are located at the correct depths and oriented in a preferential north-south direction. To explain the time-lapse data, the inversion requires unrealistically large resistivity changes with respect to the base model. We suggest that this is partly explained by unaccounted subsurface heterogeneities in the base model from which time-lapse changes are inferred.
Earthquake source tensor inversion with the gCAP method and 3D Green's functions
NASA Astrophysics Data System (ADS)
Zheng, J.; Ben-Zion, Y.; Zhu, L.; Ross, Z.
2013-12-01
We develop and apply a method to invert earthquake seismograms for source properties using a general tensor representation and 3D Green's functions. The method employs (i) a general representation of earthquake potency/moment tensors with double couple (DC), compensated linear vector dipole (CLVD), and isotropic (ISO) components, and (ii) a corresponding generalized CAP (gCap) scheme where the continuous wave trains are broken into Pnl and surface waves (Zhu & Ben-Zion, 2013). For comparison, we also use the waveform inversion method of Zheng & Chen (2012) and Ammon et al. (1998). Sets of 3D Green's functions are calculated on a grid of 1 km3 using the 3-D community velocity model CVM-4 (Kohler et al. 2003). A bootstrap technique is adopted to establish robustness of the inversion results using the gCap method (Ross & Ben-Zion, 2013). Synthetic tests with 1-D and 3-D waveform calculations show that the source tensor inversion procedure is reasonably reliable and robust. As initial application, the method is used to investigate source properties of the March 11, 2013, Mw=4.7 earthquake on the San Jacinto fault using recordings of ~45 stations up to ~0.2Hz. Both the best fitting and most probable solutions include ISO component of ~1% and CLVD component of ~0%. The obtained ISO component, while small, is found to be a non-negligible positive value that can have significant implications for the physics of the failure process. Work on using higher frequency data for this and other earthquakes is in progress.
A nonlinear inversion method for 3D electromagnetic imaging using adjoint fields
NASA Astrophysics Data System (ADS)
Dorn, O.; Bertete-Aguirre, H.; Berryman, J. G.; Papanicolaou, G. C.
1999-12-01
Electromagnetic imaging is modelled as an inverse problem for the 3D system of Maxwell's equations of which the isotropic conductivity distribution in the domain of interest has to be reconstructed. The main application we have in mind is the monitoring of conducting contaminant plumes out of surface and borehole electromagnetic imaging data. The essential feature of the method developed here is the use of adjoint fields for the reconstruction task, combined with a splitting of the data into smaller groups which define subproblems of the inversion problem. The method works iteratively, and can be considered as a nonlinear generalization of the algebraic reconstruction technique in x-ray tomography. Starting out from some initial guess for the conductivity distribution, an update for this guess is computed by solving one forward and one adjoint problem of the 3D Maxwell system at a time. Numerical experiments are performed for a layered background medium in which one or two localized (3D) inclusions are immersed. These have to be monitored out of surface to borehole and cross-borehole electromagnetic data. We show that the algorithm is able to recover a single inclusion in the earth which has high contrast to the background, and to distinguish between two separated inclusions in the earth given certain borehole geometries.
Joint earthquake source inversions using seismo-geodesy and 3-D earth models
NASA Astrophysics Data System (ADS)
Weston, J.; Ferreira, A. M. G.; Funning, G. J.
2014-08-01
A joint earthquake source inversion technique is presented that uses InSAR and long-period teleseismic data, and, for the first time, takes 3-D Earth structure into account when modelling seismic surface and body waves. Ten average source parameters (Moment, latitude, longitude, depth, strike, dip, rake, length, width and slip) are estimated; hence, the technique is potentially useful for rapid source inversions of moderate magnitude earthquakes using multiple data sets. Unwrapped interferograms and long-period seismic data are jointly inverted for the location, fault geometry and seismic moment, using a hybrid downhill Powell-Monte Carlo algorithm. While the InSAR data are modelled assuming a rectangular dislocation in a homogeneous half-space, seismic data are modelled using the spectral element method for a 3-D earth model. The effect of noise and lateral heterogeneity on the inversions is investigated by carrying out realistic synthetic tests for various earthquakes with different faulting mechanisms and magnitude (Mw 6.0-6.6). Synthetic tests highlight the improvement in the constraint of fault geometry (strike, dip and rake) and moment when InSAR and seismic data are combined. Tests comparing the effect of using a 1-D or 3-D earth model show that long-period surface waves are more sensitive than long-period body waves to the change in earth model. Incorrect source parameters, particularly incorrect fault dip angles, can compensate for systematic errors in the assumed Earth structure, leading to an acceptable data fit despite large discrepancies in source parameters. Three real earthquakes are also investigated: Eureka Valley, California (1993 May 17, Mw 6.0), Aiquile, Bolivia (1998 February 22, Mw 6.6) and Zarand, Iran (2005 May 22, Mw 6.5). These events are located in different tectonic environments and show large discrepancies between InSAR and seismically determined source models. Despite the 40-50 km discrepancies in location between previous geodetic and
Advanced Multivariate Inversion Techniques for High Resolution 3D Geophysical Modeling (Invited)
NASA Astrophysics Data System (ADS)
Maceira, M.; Zhang, H.; Rowe, C. A.
2009-12-01
We focus on the development and application of advanced multivariate inversion techniques to generate a realistic, comprehensive, and high-resolution 3D model of the seismic structure of the crust and upper mantle that satisfies several independent geophysical datasets. Building on previous efforts of joint invesion using surface wave dispersion measurements, gravity data, and receiver functions, we have added a fourth dataset, seismic body wave P and S travel times, to the simultaneous joint inversion method. We present a 3D seismic velocity model of the crust and upper mantle of northwest China resulting from the simultaneous, joint inversion of these four data types. Surface wave dispersion measurements are primarily sensitive to seismic shear-wave velocities, but at shallow depths it is difficult to obtain high-resolution velocities and to constrain the structure due to the depth-averaging of the more easily-modeled, longer-period surface waves. Gravity inversions have the greatest resolving power at shallow depths, and they provide constraints on rock density variations. Moreover, while surface wave dispersion measurements are primarily sensitive to vertical shear-wave velocity averages, body wave receiver functions are sensitive to shear-wave velocity contrasts and vertical travel-times. Addition of the fourth dataset, consisting of seismic travel-time data, helps to constrain the shear wave velocities both vertically and horizontally in the model cells crossed by the ray paths. Incorporation of both P and S body wave travel times allows us to invert for both P and S velocity structure, capitalizing on empirical relationships between both wave types’ seismic velocities with rock densities, thus eliminating the need for ad hoc assumptions regarding the Poisson ratios. Our new tomography algorithm is a modification of the Maceira and Ammon joint inversion code, in combination with the Zhang and Thurber TomoDD (double-difference tomography) program.
Finite-Element-Based Discretization and Regularization Strategies for 3D Inverse Electrocardiography
Wang, Dafang; Kirby, Robert M.; Johnson, Chris R.
2011-01-01
We consider the inverse electrocardiographic problem of computing epicardial potentials from a body-surface potential map. We study how to improve numerical approximation of the inverse problem when the finite element method is used. Being ill-posed, the inverse problem requires different discretization strategies from its corresponding forward problem. We propose refinement guidelines that specifically address the ill-posedness of the problem. The resulting guidelines necessitate the use of hybrid finite elements composed of tetrahedra and prism elements. Also in order to maintain consistent numerical quality when the inverse problem is discretized into different scales, we propose a new family of regularizers using the variational principle underlying finite element methods. These variational-formed regularizers serve as an alternative to the traditional Tikhonov regularizers, but preserves the L2 norm and thereby achieves consistent regularization in multi-scale simulations. The variational formulation also enables a simple construction of the discrete gradient operator over irregular meshes, which is difficult to define in traditional discretization schemes. We validated our hybrid element technique and the variational regularizers by simulations on a realistic 3D torso/heart model with empirical heart data. Results show that discretization based on our proposed strategies mitigates the ill-conditioning and improves the inverse solution, and that the variational formulation may benefit a broader range of potential-based bioelectric problems. PMID:21382763
3D inversion of time-lapse CSEM data for reservoir monitoring
NASA Astrophysics Data System (ADS)
Black, N.; Wilson, G. A.; Zhdanov, M. S.
2010-12-01
Effective reservoir monitoring requires time-lapse reservoir information throughout the interwell volume. The ability to understand and control reservoir behavior over the course of production allows for optimization of reservoir performance and production strategies. Good monitoring information makes it possible to improve the timing and location of new drilling (for both production and injection wells), to recognize flow paths, and to map oil that has been bypassed. Recent studies have inferred the feasibility of time-lapse marine controlled-source electromagnetic (CSEM) methods for the monitoring of offshore oil and gas fields. However, quantitative interpretations to ascertain what reservoir information may be recovered have not been performed. The time-lapse CSEM inverse problem can be highly constrained since the geometry of the reservoir is established prior from high resolution seismic surveys, rock and fluid properties are measured from well logs, and multiple history matched production scenarios are contained in dynamic reservoir models. We present a 3D inversion study of synthetic time-lapse CSEM data modeled from dynamic reservoir simulations. We demonstrate that even with few constraints on the model, the hydrocarbon-water front can be recovered from 3D inversion.
Finite Element Based Anisotropic 3D Inversion of Marine CSEM Data
NASA Astrophysics Data System (ADS)
Chung, Y.; Byun, J.
2015-12-01
In order to interpret three-dimensional (3D) marine controlled-source electromagnetic (MCSEM) data, it is critical to accurately determine electrical anisotropy because ignoring anisotropy can produce misleading artifacts. In this study, we present an inversion method for 3D subsurface imaging in media with an inhomogeneous and anisotropic conductivity distribution. Direct solvers are incorporated both in the forward and inverse problems, For the forward problem, the vector Helmholtz equation for the secondary electric field is discretized on a hexahedral mesh using edge finite elements, then a direct sparse-matrix solver is chosen to effectively reuse its factorization both in the survey simulation and Jacobian computation. The inversion method is formulated as a functional optimization with an objective functional containing terms measuring data misfit and model structure by means of smoothness and anisotropy. These measures are efficiently incorporated through the use of an iteratively reweighted least-squares scheme. The objective functional is minimized by a Gauss-Newton approach using a direct dense-matrix solver. We demonstrate the accuracy and applicability of the algorithm by testing it on synthetic data sets.
A hybrid method for inversion of 3D DC resistivity logging measurements.
Gajda-Zagórska, Ewa; Schaefer, Robert; Smołka, Maciej; Paszyński, Maciej; Pardo, David
This paper focuses on the application of hp hierarchic genetic strategy (hp-HGS) for solution of a challenging problem, the inversion of 3D direct current (DC) resistivity logging measurements. The problem under consideration has been formulated as the global optimization one, for which the objective function (misfit between computed and reference data) exhibits multiple minima. In this paper, we consider the extension of the hp-HGS strategy, namely we couple the hp-HGS algorithm with a gradient based optimization method for a local search. Forward simulations are performed with a self-adaptive hp finite element method, hp-FEM. The computational cost of misfit evaluation by hp-FEM depends strongly on the assumed accuracy. This accuracy is adapted to the tree of populations generated by the hp-HGS algorithm, which makes the global phase significantly cheaper. Moreover, tree structure of demes as well as branch reduction and conditional sprouting mechanism reduces the number of expensive local searches up to the number of minima to be recognized. The common (direct and inverse) accuracy control, crucial for the hp-HGS efficiency, has been motivated by precise mathematical considerations. Numerical results demonstrate the suitability of the proposed method for the inversion of 3D DC resistivity logging measurements.
High-resolution imaging of crustal melts using 3D full-waveform seismic inversion
NASA Astrophysics Data System (ADS)
Warner, M.; Morgan, J. V.
2013-12-01
A newly practical seismic imaging technique, 3D full-waveform inversion (FWI), now has the ability to image zones of melt and melt pathways throughout the crust with a better resolution than any other geophysical method. 3D FWI has recently changed practice within the petroleum industry where it is used to obtain high-resolution high-fidelity models of physical properties in the sub-surface that are both interpreted directly and used to improve the migration of deeper reflections. This technology has been spectacularly successful in improving the imaging of reservoirs beneath shallow heterogeneities produced by, for example, gas clouds, buried fluvial channels, carbonate reefs and salt bodies. During FWI, the sub-surface model is recovered principally by using the low-frequency transmitted, refracted portion of the wavefield which is most sensitive to the macro-velocity structure. In the petroleum industry, these inversions are now routinely performed using long-offset surface-streamer and ocean-bottom data to maximum source-receiver offsets of about 15 km, leading to a maximum penetration depth of around 5 km. Using longer offsets, it is possible to extend this technology to image deeper crustal targets. Localised zones of partial melt produce large changes in p-wave and s-wave properties that are restricted in their spatial extent, and that therefore form ideal targets for 3D FWI. We have performed a suite of tests to explore the use of 3D FWI in imaging melt distribution beneath the active volcano of Montserrat. We built a model of the subsurface using a 3D travel-time tomographic model obtained from the SEA CALIPSO experiment. We added two magma chambers in accordance with a model obtained using surface-elevation changes and geochemical data. We used a wide-angle, wide-azimuth acquisition geometry to generate a fully-elastic synthetic seismic dataset, added noise, and inverted the windowed transmitted arrivals only. We used an elastic code for the forward
Solving Dirac equations on a 3D lattice with inverse Hamiltonian and spectral methods
NASA Astrophysics Data System (ADS)
Ren, Z. X.; Zhang, S. Q.; Meng, J.
2017-02-01
A new method to solve the Dirac equation on a 3D lattice is proposed, in which the variational collapse problem is avoided by the inverse Hamiltonian method and the fermion doubling problem is avoided by performing spatial derivatives in momentum space with the help of the discrete Fourier transform, i.e., the spectral method. This method is demonstrated in solving the Dirac equation for a given spherical potential in a 3D lattice space. In comparison with the results obtained by the shooting method, the differences in single-particle energy are smaller than 10-4 MeV, and the densities are almost identical, which demonstrates the high accuracy of the present method. The results obtained by applying this method without any modification to solve the Dirac equations for an axial-deformed, nonaxial-deformed, and octupole-deformed potential are provided and discussed.
Keegan, Jennifer; Gatehouse, Peter D; Haldar, Shouvik; Wage, Ricardo; Babu-Narayan, Sonya V; Firmin, David N
2015-02-01
High resolution three-dimensional (3D) late gadolinium enhancement (LGE) imaging is performed with single R-wave gating to minimize lengthy acquisition durations. In patients with atrial fibrillation (AF), heart rate variability results in variable magnetization recovery between sequence repeats, and image quality is often poor. In this study, we implemented and tested a dynamic inversion time (dynamic-TI) scheme designed to reduce sequence sensitivity to heart rate variations. An inversion-prepared 3D segmented gradient echo sequence was modified so that the TI varied automatically from beat-to-beat (dynamic-TI) based on the time since the last sequence repeat. 3D LGE acquisitions were performed in 17 patients prior to radio frequency ablation of persistent AF both with and without dynamic-TI. Qualitative image quality scores, blood signal-to-ghosting ratios (SGRs). and blood-myocardium contrast-to-ghosting ratios (CGRs) were compared. Image quality scores were higher with dynamic-TI than without dynamic-TI (2.2 ± 0.9 vs. 1.8 ± 1.1, P = 0.008), as were blood-myocardium CGRs (13.8 ± 7.6 vs. 8.3 ± 6.1, P = 0.003) and blood SGRs (19.6 ± 8.5 vs. 13.1 ± 8.0, P = 0.003). The dynamic-TI algorithm improves image quality of 3D LGE imaging in this difficult patient population by reducing the sequence sensitivity to RR interval variations © 2014 Wiley Periodicals, Inc.
Towards Automated Seismic Moment Tensor Inversion in Australia Using 3D Structural Model
NASA Astrophysics Data System (ADS)
Hingee, M.; Tkalcic, H.; Fichtner, A.; Sambridge, M.; Kennett, B. L.; Gorbatov, A.
2009-12-01
There is significant seismic activity in the region around Australia, largely due to the plate boundaries to the north and to the east of the mainland. This seismicity poses serious seismic and tsunamigenic hazard in a wider region, and risk to coastal areas of Australia, and is monitored by Geoscience Australia (GA) using a network of permanent broadband seismometers within Australia. Earthquake and tsunami warning systems were established by the Australian Government and have been using the waveforms from the GA seismological network. The permanent instruments are augmented by non-GA seismic stations based both within and outside of Australia. In particular, seismic moment tensor (MT) solutions for events around Australia as well as local distances are useful for both warning systems and geophysical studies in general. These monitoring systems, however, currently use only one dimensional, spherically-symmetric models of the Earth for source parameter determination. Recently, a novel 3D model of Australia and the surrounding area has been developed from spectral element simulations [1], taking into account not only velocity heterogeneities, but also radial anisotropy and seismic attenuation. This development, inter alia, introduces the potential of providing significant improvements in MT solution accuracy. Allowing reliable MT solutions with reduced dependence on non-GA stations is a secondary advantage. We studied the feasibility of using 1D versus 3D structural models. The accuracy of the 3D model has been investigated, confirming that these models are in most cases superior to the 1D models. A full MT inversion method using a point source approximation was developed as the first step, keeping in mind that for more complex source time functions, a finite source inversion will be needed. Synthetic experiments have been performed with random noise added to the signal to test the code in the both 1D and 3D setting, using a precomputed library of structural Greens
NASA Astrophysics Data System (ADS)
Yang, Dikun; Oldenburg, Douglas W.; Haber, Eldad
2014-03-01
Airborne electromagnetic (AEM) methods are highly efficient tools for assessing the Earth's conductivity structures in a large area at low cost. However, the configuration of AEM measurements, which typically have widely distributed transmitter-receiver pairs, makes the rigorous modelling and interpretation extremely time-consuming in 3-D. Excessive overcomputing can occur when working on a large mesh covering the entire survey area and inverting all soundings in the data set. We propose two improvements. The first is to use a locally optimized mesh for each AEM sounding for the forward modelling and calculation of sensitivity. This dedicated local mesh is small with fine cells near the sounding location and coarse cells far away in accordance with EM diffusion and the geometric decay of the signals. Once the forward problem is solved on the local meshes, the sensitivity for the inversion on the global mesh is available through quick interpolation. Using local meshes for AEM forward modelling avoids unnecessary computing on fine cells on a global mesh that are far away from the sounding location. Since local meshes are highly independent, the forward modelling can be efficiently parallelized over an array of processors. The second improvement is random and dynamic down-sampling of the soundings. Each inversion iteration only uses a random subset of the soundings, and the subset is reselected for every iteration. The number of soundings in the random subset, determined by an adaptive algorithm, is tied to the degree of model regularization. This minimizes the overcomputing caused by working with redundant soundings. Our methods are compared against conventional methods and tested with a synthetic example. We also invert a field data set that was previously considered to be too large to be practically inverted in 3-D. These examples show that our methodology can dramatically reduce the processing time of 3-D inversion to a practical level without losing resolution
3D stochastic inversion of gravity data of Lalor volcanogenic massive sulphide, Manitoba, Canada
NASA Astrophysics Data System (ADS)
Tirdad, Shiva; Bouchedda, Abderrezak; Gloaguen, Erwan; Dupuis, Christian
2017-04-01
3D stochastic inversion of gravity data of Lalor volcanogenic massive sulphide The objective of this study is to present an algorithm for 3D stochastic inversion of gravity data, which takes into account the geological model. The obtained model is expected to permit the application of Bayesian SGS approach for metal grade estimation and compare the results with those retrieved using conventional least-squared regularized inversion. The proposed approach includes sets of geological models adjusted to the actual data without any matrix inversion as usually done in conventional approaches. The stochastic inversion seeks the conditional probability density parameters of the measured data and the known constraints of the model, unlike the conventional inversion where a single optimal model is sought. In this study, we propose a stochastic inversion method in which, the geological model of the study area is used as a training image to generate multiple scenarios by implementing multiple point simulation. In an optimization process to obtain a satisfactory match to sets of observed data, different stochastic realizations with the same overall statistical properties are iteratively linearly combined through gradual deformation. Then, we perform forward modeling on these constrained combined models to obtain measured gravity data, assuming the physical properties of each unit in our models are constant. The results are compared by the observed data to have the minimum misfit possible between the measured and observed data in order to validate the initial geological model The methodology is applied to Lalor volcanogenic massive sulphide (VMS) deposit, which is located near Snow Lake, Manitoba, Canada. The deposit is one of the largest metal deposits within Flin Flon Greenstone Belt having 25Mt reserves. There are three mineralization zones in the deposit including zinc zones, gold zones and a gold-copper zone. An analysis of physical rock properties was conducted to
3D linear inversion of magnetic susceptibility data acquired by frequency domain EMI
NASA Astrophysics Data System (ADS)
Thiesson, J.; Tabbagh, A.; Simon, F.-X.; Dabas, M.
2017-01-01
Low induction number EMI instruments are able to simultaneously measure a soil's apparent magnetic susceptibility and electrical conductivity. This family of dual measurement instruments is highly useful for the analysis of soils and archeological sites. However, the electromagnetic properties of soils are found to vary over considerably different ranges: whereas their electrical conductivity varies from ≤ 0.1 to ≥ 100 mS/m, their relative magnetic permeability remains within a very small range, between 1.0001 and 1.01 SI. Consequently, although apparent conductivity measurements need to be inverted using non-linear processes, the variations of the apparent magnetic susceptibility can be approximated through the use of linear processes, as in the case of the magnetic prospection technique. Our proposed 3D inversion algorithm starts from apparent susceptibility data sets, acquired using different instruments over a given area. A reference vertical profile is defined by considering the mode of the vertical distributions of both the electrical resistivity and of the magnetic susceptibility. At each point of the mapped area, the reference vertical profile response is subtracted to obtain the apparent susceptibility variation dataset. A 2D horizontal Fourier transform is applied to these variation datasets and to the dipole (impulse) response of each instrument, a (vertical) 1D inversion is performed at each point in the spectral domain, and finally the resulting dataset is inverse transformed to restore the apparent 3D susceptibility variations. It has been shown that when applied to synthetic results, this method is able to correct the apparent deformations of a buried object resulting from the geometry of the instrument, and to restore reliable quantitative susceptibility contrasts. It also allows the thin layer solution, similar to that used in magnetic prospection, to be implemented. When applied to field data it initially delivers a level of contrast
Monte-Carlo-based inversion scheme for 3D quantitative photoacoustic tomography
NASA Astrophysics Data System (ADS)
Kaplan, Bernhard A.; Buchmann, Jens; Prohaska, Steffen; Laufer, Jan
2017-03-01
The goal of quantitative photoacoustic tomography (qPAT) is to recover maps of the chromophore distributions from multiwavelength images of the initial pressure. Model-based inversions that incorporate the physical processes underlying the photoacoustic (PA) signal generation represent a promising approach. Monte-Carlo models of the light transport are computationally expensive, but provide accurate fluence distributions predictions, especially in the ballistic and quasi-ballistic regimes. Here, we focus on the inverse problem of 3D qPAT of blood oxygenation and investigate the application of the Monte-Carlo method in a model-based inversion scheme. A forward model of the light transport based on the MCX simulator and acoustic propagation modeled by the k-Wave toolbox was used to generate a PA image data set acquired in a tissue phantom over a planar detection geometry. The combination of the optical and acoustic models is shown to account for limited-view artifacts. In addition, the errors in the fluence due to, for example, partial volume artifacts and absorbers immediately adjacent to the region of interest are investigated. To accomplish large-scale inversions in 3D, the number of degrees of freedom is reduced by applying image segmentation to the initial pressure distribution to extract a limited number of regions with homogeneous optical parameters. The absorber concentration in the tissue phantom was estimated using a coordinate descent parameter search based on the comparison between measured and modeled PA spectra. The estimated relative concentrations using this approach lie within 5 % compared to the known concentrations. Finally, we discuss the feasibility of this approach to recover the blood oxygenation from experimental data.
3D Self-Potential Inversion for Monitoring DNAPL Contaminant Distributions
NASA Astrophysics Data System (ADS)
Minsley, B. J.; Sogade, J.; Vichabian, Y.; Morgan, F. D.
2005-05-01
Self-potential (SP) data are collected over an area known to be contaminated with Dense Non-Aqueous Phase Liquids (DNAPLs) at the Savannah River Site in South Carolina. The field experiment consists of approximately 100 SP measurements on a surface grid and in four boreholes, and is repeated after one year. DNAPLs are known to undergo redox reactions during their degradation in the environment, which is often biologically mediated. Self-potential geophysics is employed in this study because of its sensitivity to the in-situ biochemical processes that degrade the contaminants. These reactions provide an electrochemical source that is manifested as an SP signature at the measurement locations remote from the contaminated areas. 3D inversion of the SP data is therefore needed to spatially locate the distribution of sources, which is related to contaminant presence. The inversion incorporates the 3D resistivity structure collected at the same site, and is better constrained in depth by using borehole data and regularization. Ground truth information taken after the first field experiment provides concentration data with depth for several DNAPL species in five boreholes. There is a good correlation between the ground truth data and SP source inversion, though this comparison is limited by several factors: the difference in resolution of the ground truth and inverted data, and the dependence of the redox processes on other constituents that were not measured during the ground truthing, such as oxygen content or microbial presence. Inversion of the second year's dataset provides information on the changes in the contaminant distribution, either due to natural degradation or ongoing remediation.
Influence of the 3D inverse dynamic method on the joint forces and moments during gait.
Dumas, R; Nicol, E; Chèze, L
2007-10-01
The joint forces and moments are commonly used in gait analysis. They can be computed by four different 3D inverse dynamic methods proposed in the literature, either based on vectors and Euler angles, wrenches and quaternions, homogeneous matrices, or generalized coordinates and forces. In order to analyze the influence of the inverse dynamic method, the joint forces and moments were computed during gait on nine healthy subjects. A ratio was computed between the relative dispersions (due to the method) and the absolute amplitudes of the gait curves. The influence of the inverse dynamic method was negligible at the ankle (2%) but major at the knee and the hip joints (40%). This influence seems to be due to the dynamic computation rather than the kinematic computation. Compared to the influence of the joint center location, the body segment inertial parameter estimation, and more, the influence of the inverse dynamic method is at least of equivalent importance. This point should be confirmed with other subjects, possibly pathologic, and other movements.
A framework for 3D joint inversion of MT, gravity and seismic refraction data (Invited)
NASA Astrophysics Data System (ADS)
Moorkamp, M.; Jegen, M. D.; Heincke, B.; Roberts, A. W.; Hobbs, R. W.
2010-12-01
We present a 3D joint inversion framework for seismic, magnetotelluric, along with scalar and tensorial gravity data. Using optimization methods suited for large-scale data sets, parallelization of the forward problems and a flexible implementation in terms of model parameterization allows us to investigate different coupling approaches for the various physical parameters involved in the joint inversion. Here we compare two different coupling schemes; direct parameter coupling, where we calculate conductivity and density from seismic slowness, and cross-gradient coupling where each model cell has an independent value for each physical property and structural similarity is enforced through an additional term in the objective function. In both approaches we see an improvement of the inversion results over single inversions when the inverted datasets are generated from compatible models. As expected, the direct coupling approach results in a stronger interaction between the datasets and in this case better results are obtained compared to the cross-gradient coupling. In contrast, when the inverted magnetotelluric data is generated from a model that violates the parameter relationship in some regions but conforms with the cross-gradient assumptions, we obtain good results with the cross-gradient approach, while the direct coupling approach results in spurious features. This makes the cross-gradient approach the first choice for regions where a direct relationship between the physical parameters is unclear.
Adaptive image inversion of contrast 3D echocardiography for enabling automated analysis.
Shaheen, Anjuman; Rajpoot, Kashif
2015-08-01
Contrast 3D echocardiography (C3DE) is commonly used to enhance the visual quality of ultrasound images in comparison with non-contrast 3D echocardiography (3DE). Although the image quality in C3DE is perceived to be improved for visual analysis, however it actually deteriorates for the purpose of automatic or semi-automatic analysis due to higher speckle noise and intensity inhomogeneity. Therefore, the LV endocardial feature extraction and segmentation from the C3DE images remains a challenging problem. To address this challenge, this work proposes an adaptive pre-processing method to invert the appearance of C3DE image. The image inversion is based on an image intensity threshold value which is automatically estimated through image histogram analysis. In the inverted appearance, the LV cavity appears dark while the myocardium appears bright thus making it similar in appearance to a 3DE image. Moreover, the resulting inverted image has high contrast and low noise appearance, yielding strong LV endocardium boundary and facilitating feature extraction for segmentation. Our results demonstrate that the inverse appearance of contrast image enables the subsequent LV segmentation. Copyright © 2015 Elsevier Ltd. All rights reserved.
3D inversion based on multi-grid approach of magnetotelluric data from Northern Scandinavia
NASA Astrophysics Data System (ADS)
Cherevatova, M.; Smirnov, M.; Korja, T. J.; Egbert, G. D.
2012-12-01
In this work we investigate the geoelectrical structure of the cratonic margin of Fennoscandian Shield by means of magnetotelluric (MT) measurements carried out in Northern Norway and Sweden during summer 2011-2012. The project Magnetotellurics in the Scandes (MaSca) focuses on the investigation of the crust, upper mantle and lithospheric structure in a transition zone from a stable Precambrian cratonic interior to a passive continental margin beneath the Caledonian Orogen and the Scandes Mountains in western Fennoscandia. Recent MT profiles in the central and southern Scandes indicated a large contrast in resistivity between Caledonides and Precambrian basement. The alum shales as a highly conductive layers between the resistive Precambrian basement and the overlying Caledonian nappes are revealed from this profiles. Additional measurements in the Northern Scandes were required. All together data from 60 synchronous long period (LMT) and about 200 broad band (BMT) sites were acquired. The array stretches from Lofoten and Bodo (Norway) in the west to Kiruna and Skeleftea (Sweden) in the east covering an area of 500x500 square kilometers. LMT sites were occupied for about two months, while most of the BMT sites were measured during one day. We have used new multi-grid approach for 3D electromagnetic (EM) inversion and modelling. Our approach is based on the OcTree discretization where the spatial domain is represented by rectangular cells, each of which might be subdivided (recursively) into eight sub-cells. In this simplified implementation the grid is refined only in the horizontal direction, uniformly in each vertical layer. Using multi-grid we manage to have a high grid resolution near the surface (for instance, to tackle with galvanic distortions) and lower resolution at greater depth as the EM fields decay in the Earth according to the diffusion equation. We also have a benefit in computational costs as number of unknowns decrease. The multi-grid forward
Efficient linear inversion of poststack seismic data with 3-D uncertainties
NASA Astrophysics Data System (ADS)
Zunino, Andrea; Mosegaard, Klaus
2017-04-01
Large amounts of reflection seismic data are routinely collected to investigate the subsurface. This demands for fast and reliable algorithms to invert the seismic data for desired properties, such as acoustic impedance or other physical properties. The algorithm for inversion, in case of linear forward model and Gaussian uncertainties, based on the so-called least squares criterion, is well known. However, when the amount of data to be inverted is large, the size of the matrices involved grows so much that it may become impossible even to store them on disk and so calculations become impractical. Usually, to circumvent this problem, some assumptions are made, such as that of uncorrelated uncertainties both on data and model parameters, which lead to diagonal covariance matrices, and that of spatial invariance of the system, and thus the convolution approach. These simplifications alleviate the computational burden and decrease tremendously the size of arrays to be stored in memory/disk. Nevertheless, lateral and vertical correlated uncertainties both on data and model parameters are disregarded with this strategy, as well as potential spatial variance of the forward operator, often resulting in "noisy" images of the subsurface because each seismic trace is treated independently. In this study, we propose a methodology which, based on the assumption of separability and taking advantage of some properties of Kronecker products, it formulates the linear inverse problem with taking into account 3-D uncertainties through an algorithm which requires a very low memory/storage capability and is computationally very efficient compared to the classical approach. The result is a complete characterization of the so-called posterior distribution in terms of mean model and covariance. With this strategy, we can take into account the 3-D, vertical and horizontal correlation of uncertainties both on the model parameters and on the observed data, improving the final result of
3D inversion of full magnetic gradient tensor data based on hybrid regularization method
NASA Astrophysics Data System (ADS)
Ji, Shuangxi; Zhang, Huai; Wang, Yanfei; Zhao, Lingling
2017-04-01
Recently, the magnetic tensor data can be directly measured due to the latest development of superconducting quantum interference device (SQUID) based sensors, which can collect five unique magnetic gradients components (partial H_x/ partial x , partial H_x/ partial y , partial H_x/ partial z , partial H_y/ partial z ,partial H_z/ partial z ). More measurement date will bring more useful information of observed magnetic anomaly, however it still bear the computational instability problem because of the intrinsic ill-posed property in the magnetic inverse problem. Furthermore, most of research on magnetic regularization inversion only concentrate on total magnetic field or magnetic vector field, rather than the magnetic gradient tensor field. Therefore we introduce a novel 3D hybrid regularization method by MS-TV stabilizer for inversion of magnetic gradient tensor data, which is designed mainly based on the minimum support functional (MS) and total variation functional (TV), and the final regularization functional can be described as the following form: J(κ)&=1/2(G(κ)-d,wd(G(κ)-d))ΩP+α((1-λ)φpMS(κ)+λφβ TV(κ)) &=1/2(G(κ)-d,wd(G(κ)-d))ΩP +α(1-λ/2\\intΩQ(κ-κprior)2/(κ-κprior)2+e2dΩQ &+λ\\intΩQ√{|\
3-D inversion of synthetic marine magnetotelluric data: resolution and sensitivity
NASA Astrophysics Data System (ADS)
Tada, N.; Baba, K.; Siripunvaraporn, W.; Uyeshima, M.; Utada, H.
2010-12-01
In recent years, seafloor magnetotelluric (MT) observation is carried out by using an increasing number of ocean bottom electromagnetometers (OBEMs) not only along a line but also in 2-D array. Thus, imaging electrical conductivity structures under the seafloor in 3-D is now feasible. A 3-D approach is indispensable especially for marine MT data, because the electric and magnetic fields observed at the seafloor are heavily distorted by the rugged seafloor topography and the distribution of land and sea which are generally 3-D. It is very important to incorporate the topography in a 3-D model for an accurate estimation of the conductivity structure beneath seafloor that is generally more resistive than seawater by several orders of magnitude. WSINV3DMT (Siripunvaraporn et al., 2005) is one of 3-D inversion codes that are now of practical use, but the original WSINV3DMT is not applicable to marine MT data because of two reasons. 1) MT responses are calculated only at the boundary corresponding to the Earth surface. 2) We have to use fine mesh design because an observation site must locate exactly at the center of the top surface of a block, which needs large memory that even a highest performance computer can not handle. We propose an extended version of the WSINV3DMT by solving the two problems shown above so that it can be applied to the marine MT data. The extended version of the WSINV3DMT is tested using synthetic models including a 3-D anomaly, seawater and topographic variation. Here shown is an example of a checkerboard test by using a model in which 10 ohm-m and 100 ohm-m blocks are put alternately in both horizontal and vertical directions. The model is composed of 5 blocks in horizontal directions and of 4 blocks in vertical direction with a background of a 31.6 ohm-m half-space below actual topography. The calculation area in the inversion is 7440 × 7440 × 1008 km, and is discretized at 35 blocks in the x and y directions, and 69 blocks in the z
3D CSEM data inversion using Newton and Halley class methods
NASA Astrophysics Data System (ADS)
Amaya, M.; Hansen, K. R.; Morten, J. P.
2016-05-01
For the first time in 3D controlled source electromagnetic data inversion, we explore the use of the Newton and the Halley optimization methods, which may show their potential when the cost function has a complex topology. The inversion is formulated as a constrained nonlinear least-squares problem which is solved by iterative optimization. These methods require the derivatives up to second order of the residuals with respect to model parameters. We show how Green's functions determine the high-order derivatives, and develop a diagrammatical representation of the residual derivatives. The Green's functions are efficiently calculated on-the-fly, making use of a finite-difference frequency-domain forward modelling code based on a multi-frontal sparse direct solver. This allow us to build the second-order derivatives of the residuals keeping the memory cost in the same order as in a Gauss-Newton (GN) scheme. Model updates are computed with a trust-region based conjugate-gradient solver which does not require the computation of a stabilizer. We present inversion results for a synthetic survey and compare the GN, Newton, and super-Halley optimization schemes, and consider two different approaches to set the initial trust-region radius. Our analysis shows that the Newton and super-Halley schemes, using the same regularization configuration, add significant information to the inversion so that the convergence is reached by different paths. In our simple resistivity model examples, the convergence speed of the Newton and the super-Halley schemes are either similar or slightly superior with respect to the convergence speed of the GN scheme, close to the minimum of the cost function. Due to the current noise levels and other measurement inaccuracies in geophysical investigations, this advantageous behaviour is at present of low consequence, but may, with the further improvement of geophysical data acquisition, be an argument for more accurate higher-order methods like those
Levander, Alan Richard; Zelt, Colin A.
2015-03-17
The work plan for this project was to develop and apply advanced seismic reflection and wide-angle processing and inversion techniques to high resolution seismic data for the shallow subsurface to seismically characterize the shallow subsurface at hazardous waste sites as an aid to containment and cleanup activities. We proposed to continue work on seismic data that we had already acquired under a previous DoE grant, as well as to acquire additional new datasets for analysis. The project successfully developed and/or implemented the use of 3D reflection seismology algorithms, waveform tomography and finite-frequency tomography using compressional and shear waves for high resolution characterization of the shallow subsurface at two waste sites. These two sites have markedly different near-surface structures, groundwater flow patterns, and hazardous waste problems. This is documented in the list of refereed documents, conference proceedings, and Rice graduate theses, listed below.
The 3D inversion of airborne gamma-ray spectrometric data
NASA Astrophysics Data System (ADS)
Minty, Brian; Brodie, Ross
2016-07-01
We present a new method for the inversion of airborne gamma-ray spectrometric line data to a regular grid of radioelement concentration estimates on the ground. The method incorporates the height of the aircraft, the 3D terrain within the field of view of the spectrometer, the directional sensitivity of rectangular detectors, and a source model comprising vertical rectangular prisms with the same horizontal dimensions as the required grid cell size. The top of each prism is a plane surface derived from a best-fit plane to the digital elevation model of the earth's surface within each grid cell area. The method is a significant improvement on current methods, and gives superior interpolation between flight lines. It also eliminates terrain effects that would normally remain in the data after the conventional processing of these data assuming a flat-earth model.
NASA Astrophysics Data System (ADS)
Yang, Pengliang; Brossier, Romain; Métivier, Ludovic; Virieux, Jean
2016-10-01
In this paper, we study 3-D multiparameter full waveform inversion (FWI) in viscoelastic media based on the generalized Maxwell/Zener body including arbitrary number of attenuation mechanisms. We present a frequency-domain energy analysis to establish the stability condition of a full anisotropic viscoelastic system, according to zero-valued boundary condition and the elastic-viscoelastic correspondence principle: the real-valued stiffness matrix becomes a complex-valued one in Fourier domain when seismic attenuation is taken into account. We develop a least-squares optimization approach to linearly relate the quality factor with the anelastic coefficients by estimating a set of constants which are independent of the spatial coordinates, which supplies an explicit incorporation of the parameter Q in the general viscoelastic wave equation. By introducing the Lagrangian multipliers into the matrix expression of the wave equation with implicit time integration, we build a systematic formulation of multiparameter FWI for full anisotropic viscoelastic wave equation, while the equivalent form of the state and adjoint equation with explicit time integration is available to be resolved efficiently. In particular, this formulation lays the foundation for the inversion of the parameter Q in the time domain with full anisotropic viscoelastic properties. In the 3-D isotropic viscoelastic settings, the anelastic coefficients and the quality factors using bulk and shear moduli parametrization can be related to the counterparts using P and S velocity. Gradients with respect to any other parameter of interest can be found by chain rule. Pioneering numerical validations as well as the real applications of this most generic framework will be carried out to disclose the potential of viscoelastic FWI when adequate high-performance computing resources and the field data are available.
Inverse modeling of InSAR and ground leveling data for 3D volumetric strain distribution
NASA Astrophysics Data System (ADS)
Gallardo, L. A.; Glowacka, E.; Sarychikhina, O.
2015-12-01
Wide availability of modern Interferometric Synthetic aperture Radar (InSAR) data have made possible the extensive observation of differential surface displacements and are becoming an efficient tool for the detailed monitoring of terrain subsidence associated to reservoir dynamics, volcanic deformation and active tectonism. Unfortunately, this increasing popularity has not been matched by the availability of automated codes to estimate underground deformation, since many of them still rely on trial-error subsurface model building strategies. We posit that an efficient algorithm for the volumetric modeling of differential surface displacements should match the availability of current leveling and InSAR data and have developed an algorithm for the joint inversion of ground leveling and dInSAR data in 3D. We assume the ground displacements are originated by a stress free-volume strain distribution in a homogeneous elastic media and determined the displacement field associated to an ensemble of rectangular prisms. This formulation is then used to develop a 3D conjugate gradient inversion code that searches for the three-dimensional distribution of the volumetric strains that predict InSAR and leveling surface displacements simultaneously. The algorithm is regularized applying discontinuos first and zero order Thikonov constraints. For efficiency, the resulting computational code takes advantage of the resulting convolution integral associated to the deformation field and some basic tools for multithreading parallelization. We extensively test our algorithm on leveling and InSAR test and field data of the Northwest of Mexico and compare to some feasible geological scenarios of underground deformation.
3-D Inversion of MT Data for Imaging Deformation Fronts in NW Poland
NASA Astrophysics Data System (ADS)
Ślęzak, Katarzyna; Jóźwiak, Waldemar; Nowożyński, Krzysztof; Brasse, Heinrich
2016-07-01
The Pomerania region (northwest part of Poland) occupies a significant position, where the largest European tectonic boundary is situated. This is the area of the contact between the East European Craton (EEC) and the Paleozoic Platform (PP) and it is known as the Trans-European Suture Zone (TESZ). The TESZ was formed during Paleozoic time as a consequence of the collision of several crustal units and it extends from the Black Sea in the southeast to the British Isles in the northwest. It is a region of key importance for our understanding of the tectonic history of Europe. Previous magnetotelluric (MT) results, based on 2-D inverse modeling, show that the contact zone is of lithospheric discontinuity character and there are distinct differences in geoelectric structures between the Precambrian EEC, transitional zone (TESZ), and the younger PP. The presence of a significant conductor at mid and lower crustal depths was also shown. Thus, the main aim of the research presented here was to obtain detailed, 3-D images of electrical conductivity in the crust and upper mantle and its regional distribution below the TESZ in the northwest part of Poland. To accomplish this task we applied the latest 3-D inversion codes, which allowed us to get more realistic model geometries. Additionally, to confirm and complement the study, the Horizontal Magnetic Tensor (HMT) analysis was realized. This method gives us an opportunity to efficiently locate the position of well-conducting structures. As a result we obtain a clearer, three-dimensional model of conductivity distribution, where highly conductive rock complexes appear which we tentatively connected to deformation fronts.
Review on applications of 3D inverse design method for pump
NASA Astrophysics Data System (ADS)
Yin, Junlian; Wang, Dezhong
2014-05-01
The 3D inverse design method, which methodology is far superior to the conventional design method that based on geometrical description, is gradually applied in pump blade design. However, no complete description about the method is outlined. Also, there are no general rules available to set the two important input parameters, blade loading distribution and stacking condition. In this sense, the basic theory and the mechanism why the design method can suppress the formation of secondary flow are summarized. And also, several typical pump design cases with different specific speeds ranging from centrifugal pump to axial pump are surveyed. The results indicates that, for centrifugal pump and mixed pump or turbine, the ratio of blade loading on the hub to that on the shroud is more than unit in the fore part of the blade, whereas in the aft part, the ratio is decreased to satisfy the same wrap angle for hub and shroud. And the choice of blade loading type depends on the balancing of efficiency and cavitation. If the cavitation is more weighted, the better choice is aft-loaded, otherwise, the fore-loaded or mid-loaded is preferable to improve the efficiency. The stacking condition, which is an auxiliary to suppress the secondary flow, can have great effect on the jet-wake outflow and the operation range for pump. Ultimately, how to link the design method to modern optimization techniques is illustrated. With the know-how design methodology and the know-how systematic optimization approach, the application of optimization design is promising for engineering. This paper summarizes the 3D inverse design method systematically.
Inverse protein folding in 3D hexagonal prism lattice under HPC model.
Khodabakhshi, Alireza Hadj; Manuch, Ján; Rafiey, Arash; Gupta, Arvind
2009-06-01
The inverse protein folding problem is that of designing an amino acid sequence which has a prescribed native protein fold. This problem arises in drug design where a particular structure is necessary to ensure proper protein-protein interactions. Previously, tubular structures for a three-dimensional (3D) hexagonal prism lattice were introduced and their stability was formally proved for simple instances under the hydrophobic-polar (HP) model of Dill. In this article, we generalize the design of tubular structures to allow for much larger variety of designable structures by allowing branching of tubes. Our generalized design could be used to roughly approximate given 3D shapes in the considered lattice. Although the generalized tubular structures are not stable under the HP model, we can prove that a simple instance of generalized tubular structures is structurally stable (all native folds have the designed shape) under a refined version of the HP model, called the HPC model. We conjecture that there is a way to choose which hydrophobic monomers are cysteines in all generalized tubular structures such that the designed proteins are structurally stable under the HPC model.
3D elastic full waveform inversion: case study from a land seismic survey
NASA Astrophysics Data System (ADS)
Kormann, Jean; Marti, David; Rodriguez, Juan-Esteban; Marzan, Ignacio; Ferrer, Miguel; Gutierrez, Natalia; Farres, Albert; Hanzich, Mauricio; de la Puente, Josep; Carbonell, Ramon
2016-04-01
Full Waveform Inversion (FWI) is one of the most advanced processing methods that is recently reaching a mature state after years of solving theoretical and technical issues such as the non-uniqueness of the solution and harnessing the huge computational power required by realistic scenarios. BSIT (Barcelona Subsurface Imaging Tools, www.bsc.es/bsit) includes a FWI algorithm that can tackle with very complex problems involving large datasets. We present here the application of this system to a 3D dataset acquired to constrain the shallow subsurface. This is where the wavefield is the most complicated, because most of the wavefield conversions takes place in the shallow region and also because the media is much more laterally heterogeneous. With this in mind, at least isotropic elastic approximation would be suitable as kernel engine for FWI. The current study explores the possibilities to apply elastic isotropic FWI using only the vertical component of the recorded seismograms. The survey covers an area of 500×500 m2, and consists in a receivers grid of 10 m×20 m combined with a 250 kg accelerated weight-drop as source on a displaced grid of 20 m×20 m. One of the main challenges in this case study is the costly 3D modeling that includes topography and substantial free surface effects. FWI is applied to a data subset (shooting lines 4 to 12), and is performed for 3 frequencies ranging from 15 to 25 Hz. The starting models are obtained from travel-time tomography and the all computation is run on 75 nodes of Mare Nostrum supercomputer during 3 days. The resulting models provide a higher resolution of the subsurface structures, and show a good correlation with the available borehole measurements. FWI allows to extend in a reliable way this 1D knowledge (borehole) to 3D.
KOALA: 3-D shape of asteroids from multi-data inversion
NASA Astrophysics Data System (ADS)
Carry, B.; Kaasalainen, M.; Merline, W. J.; Drummond, J. D.; Durech, J.; Berthier, J.; Conrad, A.
2011-10-01
We describe our on-going observing program to determine the physical properties of asteroids from groundbased facilities. We combine disk-resolved images from adaptive optics, optical lightcurves, and stellar occultations to put tighter constraints on the spin, 3-D shape, and size of asteroids. We will discuss the relevance of the determination of physical properties to help understand the asteroid population (e.g., density, composition, and non-gravitational forces). We will then briefly describe our multi-data inversion algorithm KOALA (Carry et al. 2010a, Kaasalainen 2011, see also Kaasalainen et al., same meeting), which allows the determination of certain physical properties of an asteroid from the combination of different techniques of observation. A comparison of results obtained with KOALA on asteroid (21) Lutetia, prior to the ESA Rosetta flyby, with the high spatial resolution images returned from that flyby, will then be presented, showing the high accuracy of KOALA inversion. Finally, we will describe our current development of the algorithm, and focus on examples of other asteroids currently being studied with KOALA.
3-D acoustic waveform simulation and inversion at Yasur Volcano, Vanuatu
NASA Astrophysics Data System (ADS)
Iezzi, A. M.; Fee, D.; Matoza, R. S.; Austin, A.; Jolly, A. D.; Kim, K.; Christenson, B. W.; Johnson, R.; Kilgour, G.; Garaebiti, E.; Kennedy, B.; Fitzgerald, R.; Key, N.
2016-12-01
Acoustic waveform inversion shows promise for improved eruption characterization that may inform volcano monitoring. Well-constrained inversion can provide robust estimates of volume and mass flux, increasing our ability to monitor volcanic emissions (potentially in real-time). Previous studies have made assumptions about the multipole source mechanism, which can be thought of as the combination of pressure fluctuations from a volume change, directionality, and turbulence. This infrasound source could not be well constrained up to this time due to infrasound sensors only being deployed on Earth's surface, so the assumption of no vertical dipole component has been made. In this study we deploy a high-density seismo-acoustic network, including multiple acoustic sensors along a tethered balloon around Yasur Volcano, Vanuatu. Yasur has frequent strombolian eruptions from any one of its three active vents within a 400 m diameter crater. The third dimension (vertical) of pressure sensor coverage allows us to begin to constrain the acoustic source components in a profound way, primarily the horizontal and vertical components and their previously uncharted contributions to volcano infrasound. The deployment also has a geochemical and visual component, including FLIR, FTIR, two scanning FLYSPECs, and a variety of visual imagery. Our analysis employs Finite-Difference Time-Domain (FDTD) modeling to obtain the full 3D Green's functions for each propagation path. This method, following Kim et al. (2015), takes into account realistic topographic scattering based on a digital elevation model created using structure-from-motion techniques. We then invert for the source location and source-time function, constraining the contribution of the vertical sound radiation to the source. The final outcome of this inversion is an infrasound-derived volume flux as a function of time, which we then compare to those derived independently from geochemical techniques as well as the inversion of
NASA Astrophysics Data System (ADS)
Spicer, B.; Morris, B.; Ugalde, H.
2011-09-01
Hosted within the Pacquet Harbour Group (PHG) on the Baie Verte Peninsula of north-central Newfoundland, the Rambler rhyolite is a 487 Ma unit of felsic tuffs, flows and subvolcanic intrusive rocks. The PHG has been affected by multiple phases of deformation with the youngest D4 deformation event producing broad northeast plunging upright cross folds in the Rambler rhyolite. Fold culminations on the upper bounding surface of the rhyolite host Cu +/- Au volcanogenic massive sulfide deposits (e.g. Rambler and Ming mines). Geophysical inversions of recently acquired high resolution gravity and magnetic data have been implemented to determine the extent of the fold axis (dome) at depth. To direct the outcome of the inversion process towards a more geologically reasonable solution this study outlines a procedure which permits the inclusion of known geological and geophysical constraints into the input (reference) model for inversion using the MAG3D and GRAV3D algorithms provided by the University of British Columbia Geophysical Inversion Facility. Reference model constraints included surficial geological contacts as defined by aeromagnetic data, and subsurface distribution of physical property variations from a series of drill-hole logs. The output (computed) model images the surface of the rhyolite dome as dipping roughly 40° to the northeast as a series of voxels with density values ranging from 2.71 to 2.75 g/cm3. While previously published ore deposit models parallel this structure in the near surface, results from these inversions suggest deeper exploration may be favorable. Magnetic inversion modeling has not provided any insight into dome morphology however it outlines the distribution of gabbroic dykes surrounding the dome.
An optimal transport approach for seismic tomography: application to 3D full waveform inversion
NASA Astrophysics Data System (ADS)
Métivier, L.; Brossier, R.; Mérigot, Q.; Oudet, E.; Virieux, J.
2016-11-01
the L 2 distance, in 2D and 3D contexts.
Centroid Moment Tensor Inversion in a 3D heterogeneous Earth: Application to the Australasian region
NASA Astrophysics Data System (ADS)
Hejrani, B.; Tkalcic, H.; Fichtner, A.
2015-12-01
radially anisotropic structure: new insights into present and past states of the Australasian upper mantle. Earth Planet. Sci. Lett. 290, 270-280. Hingee, M., Tkalčić, H., Fichtner A., Sambridge, M., 2011. Moment tensor inversion using a 3-D structural model: Applications for the Australian region, Geophys. J. Int., 184(2), 949-964.
Eichinger, P; Kirschke, J S; Hoshi, M-M; Zimmer, C; Mühlau, M; Riederer, I
2017-07-27
The double inversion recovery sequence is known to be very sensitive and specific for MS-related lesions. Our aim was to compare the sensitivity of pre- and postcontrast images of 3D double inversion recovery and conventional 3D T1-weighted images for the detection of contrast-enhancing MS-related lesions in the brain to analyze whether double inversion recovery could be as effective as T1WI. A postcontrast 3D double inversion recovery sequence was acquired in addition to the standard MR imaging protocol at 3T, including pre- and postcontrast 3D T1WI sequences as well as precontrast double inversion recovery of 45 consecutive patients with MS or clinically isolated syndrome between June and December 2013. Two neuroradiologists independently assessed precontrast, postcontrast, and subtraction images of double inversion recovery as well as T1WI to count the number of contrast-enhancing lesions. Afterward, a consensus reading was performed. Lin concordance was calculated between both radiologists, and differences in lesion detectability were assessed with the Student t test. Additionally, the contrast-to-noise ratio was calculated. Significantly more contrast-enhancing lesions could be detected with double inversion recovery compared with T1WI (16%, 214 versus 185, P = .007). The concordance between both radiologists was almost perfect (ρc = 0.94 for T1WI and ρc = 0.98 for double inversion recovery, respectively). The contrast-to-noise ratio was significantly higher in double inversion recovery subtraction images compared with T1-weighted subtraction images (double inversion recovery, 14.3 ± 5.5; T1WI, 6.3 ± 7.1; P < .001). Pre- and postcontrast double inversion recovery enables better detection of contrast-enhancing lesions in MS in the brain compared with T1WI and may be considered an alternative to the standard MR imaging protocol. © 2017 American Society of Neuroradiology.
Understanding how Fault-bounded Blocks Deform in 3D by Inverse Modelling
NASA Astrophysics Data System (ADS)
Jouen, G.; White, N.
2004-05-01
Normal faults play a crucial role in modifying basin stratigraphy. At the exploration scale, the internal deformation of tilted blocks is governed by the three-dimensional geometry of large-scale faults which bound these blocks. At the reservoir scale, the geometry and growth of normal faulting control the deformation of strata and the compartmentalisation of reservoir intervals. Despite their importance, large-scale normal faults are often difficult to image. The purpose of structural validation is two-fold: to determine the 3D shape of normal faults and to investigate the relationship between fault geometry and deformed stratigraphy including the intra-block faults. We have developed methods for tackling structural validation at a variety of scales in two and three dimensions. The cornerstone of our approach is the use of geophysical inverse theory to calculate optimal fault geometries from deformed strata. This approach allows us to focus on key questions: does a solution exist? Are there several possible solutions or just one unique one? In a complex normal fault system, which part of the fault controls the motion responsible for the deformation in the hanging-wall? Traditional forward modelling cannot answer these fundamental issues. We have applied the inversion on seismic data in particularly complex areas in the northern North Sea. The aims of this project are to determine the geometry of the basin-bounding fault, to assess the likelihood of out-of-plane motion as well as understanding the mode of deformation leading to the complexity of the present structure. Closely spaced inverse models show that the basin-bounding fault on the UK side is steeper and more planar than previously thought. This method also helped us to have a better view of what could have been the cause of the organisation and density of the intra-block faulting where it occurs. The North Cormorant study has shown how inverse modelling can yield important, quantitative, insights. Our
High-resolution imaging and inversion of 3D GPR data for layered media
NASA Astrophysics Data System (ADS)
Slob, Evert
2013-04-01
Ground penetrating radar is increasingly being used to provide quantitative information of layered structures. For application in civil engineering these can be roads, highway pavements, airport runways, bridges, tunnels, or buildings. Monitoring is important for the management and safety of these structures. Standard imaging uses a modeled wavefield extrapolator to image the data and the quality of the image depends heavily on the quality of the modeled extrapolator. Usually, data inversion is implemented by minimizing a cost function involving the measured data and the modeled data. The model is modified such that data computed from the model fits to the measured data. The data itself is not used, except as a measure of the model data fit. A recently developed alternative method is to use results from inverse scattering theory to first construct an image while all multiple reflections are simultaneously eliminated from the data. This image can be constructed from surface reflection data if the data allows separating the subsurface reflection response from the down going emitted field. For 3D waves in a layered medium this requires knowledge of all horizontal electric and magnetic field components. If the data is properly sampled the solution is unique. In layered media the plane wave decomposition allows computing the image for each angle of incidence separately as a function of image time that is equal to the one-way intercept time. Once the image is constructed for all available angles of incidence a simple matrix inversion leads to the desired electric permittivity and magnetic permeability values in each layer. Finally these values provide interval velocities that can be used to convert image time to depth and the inverse problem is solved. The theory requires infinite bandwidth frequency domain data, which is equivalent to measuring the true impulse response. This is not possible in practice and numerical results show that data with finite bandwidths can be
Parallel Inversion Arithmetic for 3D Multi-Wave Pre-stack Elasticity Parameters and Its Application
NASA Astrophysics Data System (ADS)
Luo, S.; Li, L.
2009-12-01
Multi-wave seismic prospect is an elastic wave prospect by which all wave fields can be achieved. We can inverse the stratum lithological parameters and elastic parameters by the multi-wave amplitude characteristics in order to get the information of the reservoirs and fluids. At present, the main methods of multi-wave inversion are post-stack inversion and single component partial-stack inversion, which are based on the approximative expressions and isotropy media. Widely known, the post-stack inversion can only be used to inverse the impedance, three lithological parameters(P wave velocity,S wave velocity and density)can not be obtained independently in this kind of method. The single component is not the whole elastic wave inversion, and the theory formula of the isotropy media is unfit for the anisotropy media inversion. Therefore, based on the anisotropy media, the method of the multi-wave associated pre-stack inversion is studied by using of the precise AVA formulae in this paper. To the questions of the lithology identification and the prediction of reservoirs, the authors studied the associated inversion of 3D lithological parameters for the anisotropy media with 3D3C data. The basic processes of the parameter inversion are as follows: (1) create the velocity model and produce the NMO gathers, (2) match the layers of the P wave with the same layers of P-SV wave, and convert AVO gathers into AVA gathers, (3) inverse the lithology parameters and anisotropy coefficients with the NMO gather, and (4) compute the elastic parameters, elastic impedance, elastic impedance grads based on the inversed parameters. Because of the huge amount of computing work of 3D pre-stack parameter inversion, the parallel arithmetic of the 3D pre-stack parameter inversion is utilized to improve the computing efficiency. Via the 3D real data processing, it is proved that this method is effective and can be applied in the oil and gas prediction of the reservoirs.
NASA Astrophysics Data System (ADS)
Kim, B.; Byun, J.; Seol, S. J.; Jeong, S.; Chung, Y.; Kwon, T.
2015-12-01
For many decades, gas hydrates have been received great attention as a potential source of natural gas. Therefore, the detailed information of structures of buried gas hydrates and their concentrations are prerequisite for the production for the gas hydrate as a reliable source of alternate energy. Recently, for this reason, a lot of gas hydrate assessment methods have been proposed by many researchers. However, it is still necessary to establish as new method for the further improvement of the accuracy of the 3D gas hydrate distribution. In this study, we present a 3D joint inversion method that provides superior quantitative information of gas hydrate distributions using 3D seismic data obtained by ocean-bottom cable (OBC) and marine controlled-source electromagnetic (CSEM) data. To verify our inversion method, we first built the general 3D gas hydrate model containing vertical methane-flow pathways. With the described model, we generated synthetic 3D OBC data and marine CSEM data using finite element modeling algorithms, respectively. In the joint inversion process, to obtain the high-resolution volumetric P-wave velocity structure, we applied the 3D full waveform inversion algorithm to the acquired OBC data. After that, the obtained P-wave velocity model is used as the structure constraint to compute cross-gradients with the updated resistivity model in the EM inversion process. Finally, petrophysical relations were applied to estimate volumetric gas hydrate concentrations. The proposed joint inversion process makes possible to obtain more precise quantitative gas hydrate assessment than inversion processes using only seismic or EM data. This technique can be helpful for accurate decision-making in gas hydrate development as well as in their production monitoring.
NASA Astrophysics Data System (ADS)
Beauprêtre, S.; Manighetti, I.; Garambois, S.; Malavieille, J.; Dominguez, S.
2013-08-01
earthquake slips on faults are commonly determined by measuring morphological offsets at current ground surface. Because those offsets might not always be well preserved, we examine whether the first 10 m below ground surface contains relevant information to complement them. We focus on the Te Marua site, New Zealand, where 11 alluvial terraces have been dextrally offset by the Wellington fault. We investigated the site using pseudo-3D Ground Penetrating Radar and also produced a high-resolution digital elevation model (DEM) of the zone to constrain the surface slip record. The GPR data reveal additional information: (1) they image the 3D stratigraphic architecture of the seven youngest terraces and show that they are strath terraces carved into graywacke bedrock. Each strath surface is overlain by 3-5 m of horizontally bedded gravel sheets, including two pronounced and traceable reflectors; (2) thanks to the multilayer architecture, terrace risers and channels are imaged at three depths and their lateral offsets can be measured three to four times, constraining respective offsets and their uncertainties more reliably; and (3) the offsets are better preserved in the subsurface than at the ground surface, likely due to subsequent erosion-deposition on the latter. From surface and subsurface data, we infer that Te Marua has recorded six cumulative offsets of 2.9, 7.6, 18, 23.2, 26, and 31 m (± 1-2 m). Large earthquakes on southern Wellington fault might produce 3-5 m of slip, slightly less than previously proposed. Pseudo-3D GPR thus provides a novel paleoseismological tool to complement and refine surface investigations.
NASA Astrophysics Data System (ADS)
Hu, J.; Lokier, S. W.
2012-04-01
This paper presents the results of three dimensional sequence stratigraphic forward modelling of the Aptian age Shu'aiba Formation from Abu Dhabi, United Arab Emirates (UAE). The Shu'aiba Formation lies within the uppermost part of the Lower Cretaceous Thamama Group and forms one of the most prolific hydrocarbon reservoir intervals of the Middle East with production dating back to the 1960's. The Shu'aiba Formation developed as a series of laterally-extensive shallow-water carbonate platforms in an epeiric sea that extended over the northern margin of the African-Arabian Plate. This shallow sea was bounded by the Arabian Shield to the west and the passive margin with the Neo-Tethys Ocean towards the north and east (Droste, 2010). The exposed Arabian Shield acted as a source of siliciclastic sediments to westernmost regions, however, more offshore areas were dominated by shallow-water carbonate deposition. Carbonate production was variously dominated by Lithocodium-Baccinella, orbitolinid foraminifera and rudist bivalves depending on local conditions. While there have been numerous studies of this important stratigraphic interval (for examples see van Buchem et al., 2010), there has been little attempt to simulate the sequence stratigraphic development of the formation. During the present study modelling was undertaken utilising the CARBONATE-3D stratigraphic forward modelling software (Warrlich et al., 2008; Warrlich et al., 2002)) thus allowing for the control of a diverse range of internal and external parameters on carbonate sequence development. This study focuses on platform development in the onshore Bu Hasa Field - the first giant oilfield to produce from the Shu'aiba Formation in Abu Dhabi. The carbonates of the Bu Hasa field were deposited on the southwest slope of the intra-shelf Bab Basin, siliciclastic content is minor. Initially these carbonates were algal dominated with rudist mounds becoming increasingly important over time (Alsharhan, 1987
Evaluation of 3D Inverse Code Using Rotor 67 as Test Case
NASA Technical Reports Server (NTRS)
Dang, T.
1998-01-01
A design modification of Rotor 67 is carried out with a full 3D inverse method. The blade camber surface is modified to produce a prescribed pressure loading distribution, with the blade tangential thickness distribution and the blade stacking line at midchord kept the same as the original Rotor 67 design. Because of the inviscid-flow assumption used in the current version of the method, Rotor 67 geometry is modified for use at a design point different from the original design value. A parametric study with the prescribed pressure loading distribution yields the following results. In the subsonic section, smooth pressure loading shapes generally produce blades with well-behaved blade surface pressure distributions. In the supersonic section, the study shows that the strength and position of the passage shock correlate with the characteristics of the blade pressure loading shape. In general, "smooth" prescribed blade pressure loading distributions generate blade designs with reverse cambers which have the effect of weakening the passage shock.
Statistical Inverse Ray Tracing for Image-Based 3D Modeling.
Liu, Shubao; Cooper, David B
2014-10-01
This paper proposes a new formulation and solution to image-based 3D modeling (aka "multi-view stereo") based on generative statistical modeling and inference. The proposed new approach, named statistical inverse ray tracing, models and estimates the occlusion relationship accurately through optimizing a physically sound image generation model based on volumetric ray tracing. Together with geometric priors, they are put together into a Bayesian formulation known as Markov random field (MRF) model. This MRF model is different from typical MRFs used in image analysis in the sense that the ray clique, which models the ray-tracing process, consists of thousands of random variables instead of two to dozens. To handle the computational challenges associated with large clique size, an algorithm with linear computational complexity is developed by exploiting, using dynamic programming, the recursive chain structure of the ray clique. We further demonstrate the benefit of exact modeling and accurate estimation of the occlusion relationship by evaluating the proposed algorithm on several challenging data sets.
Chern insulators without band inversion in Mo S2 monolayers with 3 d adatoms
NASA Astrophysics Data System (ADS)
Wei, Xinyuan; Zhao, Bao; Zhang, Jiayong; Xue, Yang; Li, Yun; Yang, Zhongqin
2017-02-01
Electronic and topological properties of Mo S2 monolayers endowed with 3 d transition metal (TM) adatoms (V-Fe) are explored by using ab initio methods and k .p models. Without the consideration of the Hubbard U interaction, the V, Cr, and Fe adatoms tend to locate on the top of the Mo atoms, while the most stable site for the Mn atom is at the hollow position of the Mo-S hexagon. After the Hubbard U is applied, the most stable sites of all the systems become the top of the Mo atoms. Chern insulators without band inversion are achieved in these systems. The V and Fe adsorption systems are the best candidates to produce the topological states. The k .p model calculations indicate that these topological states are determined by the TM magnetism, the C3 v crystal field from the Mo S2 substrate, and the TM atomic spin-orbit coupling (SOC). The special two-meron pseudospin texture is found to contribute to the topology. The apparent difference between the Berry curvatures for the V and Fe adsorption systems is also explored. Our results widen the understanding of the Chern insulators and are helpful for the applications of the Mo S2 monolayers in the future electronics and spintronics.
NASA Astrophysics Data System (ADS)
Preston, Leiph Alexander
We develop and apply a non-linear inversion of direct and wide-angle reflection travel times for 3-D P-wave velocity structure, earthquake hypocenters, and reflector geometry under NW Washington focusing on the structure of the subducting Juan de Fuca plate. The first-arrival travel times are derived from both active-source experiments and from local earthquakes. The reflection arrivals were picked from data collected during the 1998 Wet SHIPS active-source experiment, which consisted of air-gun sources within the inland water-ways of NW Washington and SW British Columbia to land-based stations. Our inversion procedure reduces the well-known trade-off between reflector position and the velocities above it by the combination of simultaneous inversion and adequate crossing paths. We interpret the wide-angle reflector as the Moho of the subducting Juan de Fuca slab. The relocated intraslab earthquakes separate into two groups: those located up-dip of the 45km reflector depth contour generally lie below the reflector in material whose velocity exceeds 7.7km/s, placing them within the subducting mantle, while those down-dip of this contour occur within material whose velocities are 6.8--7.5km/s, placing them within subducted oceanic crust. We interpret these groups of earthquakes as resulting from serpentine dehydration in the subducted mantle and the basalt to eclogite transformation in the subducted crust. We have performed velocity checkerboard, slab velocity resolution, and parameter sensitivity tests to estimate our ability to resolve the relationship among the reflector, intraslab hypocenters, and slab velocity structure. These tests indicate we have the necessary resolvability and can distinguish the relative locations among the velocities, reflector, and intraslab hypocenters within the subducting slab to +/-2km. The occurrence of events within the subducted mantle geometrically allows for larger magnitude earthquakes than could occur if they were confined to
Xie, G.; Li, J.; Majer, E.; Zuo, D.
1998-07-01
This paper describes a new 3D parallel GILD electromagnetic (EM) modeling and nonlinear inversion algorithm. The algorithm consists of: (a) a new magnetic integral equation instead of the electric integral equation to solve the electromagnetic forward modeling and inverse problem; (b) a collocation finite element method for solving the magnetic integral and a Galerkin finite element method for the magnetic differential equations; (c) a nonlinear regularizing optimization method to make the inversion stable and of high resolution; and (d) a new parallel 3D modeling and inversion using a global integral and local differential domain decomposition technique (GILD). The new 3D nonlinear electromagnetic inversion has been tested with synthetic data and field data. The authors obtained very good imaging for the synthetic data and reasonable subsurface EM imaging for the field data. The parallel algorithm has high parallel efficiency over 90% and can be a parallel solver for elliptic, parabolic, and hyperbolic modeling and inversion. The parallel GILD algorithm can be extended to develop a high resolution and large scale seismic and hydrology modeling and inversion in the massively parallel computer.
Wang, G.L.; Chew, W.C.; Cui, T.J.; Aydiner, A.A.; Wright, D.L.; Smith, D.V.
2004-01-01
Three-dimensional (3D) subsurface imaging by using inversion of data obtained from the very early time electromagnetic system (VETEM) was discussed. The study was carried out by using the distorted Born iterative method to match the internal nonlinear property of the 3D inversion problem. The forward solver was based on the total-current formulation bi-conjugate gradient-fast Fourier transform (BCCG-FFT). It was found that the selection of regularization parameter follow a heuristic rule as used in the Levenberg-Marquardt algorithm so that the iteration is stable.
NASA Astrophysics Data System (ADS)
Dong, H.; Kun, Z.; Zhang, L.
2015-12-01
This magnetotelluric (MT) system contains static shift correction and 3D inversion. The correction method is based on the data study on 3D forward modeling and field test. The static shift can be detected by the quantitative analysis of apparent parameters (apparent resistivity and impedance phase) of MT in high frequency range, and completed correction with inversion. The method is an automatic processing technology of computer with zero-cost, and avoids the additional field work and indoor processing with good results shown in Figure 1a-e. Figure 1a shows a normal model (I) without any local heterogeneity. Figure 1b shows a static-shifted model (II) with two local heterogeneous bodies (10 and 1000 ohm.m). Figure 1c is the inversion result (A) for the synthetic data generated from model I. Figure 1d is the inversion result (B) for the static-shifted data generated from model II. Figure 1e is the inversion result (C) for the static-shifted data from model II, but with static shift correction. The results show that the correction method is useful. The 3D inversion algorithm is improved base on the NLCG method of Newman & Alumbaugh (2000) and Rodi & Mackie (2001). For the algorithm, we added the frequency based parallel structure, improved the computational efficiency, reduced the memory of computer, added the topographic and marine factors, and added the constraints of geology and geophysics. So the 3D inversion could even work in PAD with high efficiency and accuracy. The application example of theoretical assessment in oil and gas exploration is shown in Figure 1f-i. The synthetic geophysical model consists of five layers (from top to downwards): shale, limestone, gas, oil, groundwater and limestone overlying a basement rock. Figure 1f-g show the 3D model and central profile. Figure 1h shows the centrel section of 3D inversion, the resultsd show a high degree of reduction in difference on the synthetic model. Figure 1i shows the seismic waveform reflects the
Regional conductivity structure of Cascadia from 3D inversion of USArray magnetotelluric data
NASA Astrophysics Data System (ADS)
Egbert, G. D.; Patro, P. K.
2008-12-01
Magnetotelluric (MT) data are being acquired in a series of temporary arrays deployed across the continental US through EMScope, a part of the USArray component of EarthScope. Initial deployments in 2006 and 2007 acquired data at 110 sites covering the US Pacific Northwest. The MT sites, distributed with the same nominal spacing as the USArray seismic transportable array (~75 km), produced data in the period range 10- 20,000s of very good to excellent quality. The most striking and robust feature revealed by 3D inversion of this dataset is an extensive lower crustal conductor covering most of the study area southeast of a line running from the California border at the coast to the Blue Mountains of Northeastern Oregon. The conductance of this layer, which is about 15 km thick with a top at roughly 20 km depth, exceeds 3000 S beneath the he Northwest Basin and Range (BR) province of southeastern Oregon. The high conductivity in this region is inferred to result from fluids - including possibly partial melt at depth - associated with magmatic underplating and BR extension. The lower crust is much more resistive beneath the Coast Range, Willamette Valley and Puget Lowlands of Western Washington and Oregon, and beneath the Columbia Plateau. This area of resistive crust, which was derived from a large fragment of thickened oceanic lithosphere that was accreted to North America at approximately 48 Ma ("Siletzia"), is revealed by geological and geodetic studies to be strong, accommodating tectonic stresses through rigid block rotations. In contrast, the area to the southeast characterized by high conductivity in the lower crust is actively deforming, consistent with an important role for fluids in weakening of continental crust. The resistive Siletzia crust is broken by an elongated N-S zone of high conductivity beneath the Cascade volcanoes. High conductivities beneath the volcanoes also most likely reflect the presence of interconnected fluids, in this case released
NASA Astrophysics Data System (ADS)
Aboud, Essam; El-shrief, Adel; Alqahtani, Faisal; Mogren, Saad
2017-04-01
On 19 May, 2009, an earthquake of magnitude (M=5.4) shocked the most volcanically active recent basaltic fields, Luynnier volcanic field, northwestern Saudi Arabia. This event was the largest recorded one since long time ago. Government evacuated the surrounding residents around the epicenter for over 3 months away from any future volcanic activity. The seismic event caused damages to buildings in the village around the epicenter and resulted in surface fissure trending in NNW-SSE direction with about 8 km length. Seismologists from Saudi Geological Survey (SGS) worked out on locating the epicenter and the cause of this earthquake. They collected seismic data from Saudi Geological Surveys Station Network as well as installed broadband seismic stations around the region of the earthquake. They finally concluded that the main cause of the M=5.4 event is dike intrusion at depth of about 5 km (not reached to the surface). In the present work, we carried out detailed ground/airborne gravity survey around the surficial fissure to image the subsurface volcanic structure where about 380 gravity stations were recorded covering the main fissure in an area of 600 km2. Gravity data was analyzed using CET edge detection tools and 3D inversion technique. The results revealed that, there is a magma chamber/body beneath the surface at 5-20 km depth and the main reason for the M=5.4 earthquake is tectonic settings of the Red Sea. Additionally, the area is characterized by set of faults trending in NW direction, parallel to the Red Sea, and most of the volcanic cones were located on faults/contacts implying that, they are structurally controlled. The 8-km surficial crack is extended SE underneath the surface.
NASA Astrophysics Data System (ADS)
Miensopust, Marion P.; Queralt, Pilar; Jones, Alan G.; 3D MT modellers
2013-06-01
Over the last half decade the need for, and importance of, three-dimensional (3-D) modelling of magnetotelluric (MT) data have increased dramatically and various 3-D forward and inversion codes are in use and some have become commonly available. Comparison of forward responses and inversion results is an important step for code testing and validation prior to `production' use. The various codes use different mathematical approximations to the problem (finite differences, finite elements or integral equations), various orientations of the coordinate system, different sign conventions for the time dependence and various inversion strategies. Additionally, the obtained results are dependent on data analysis, selection and correction as well as on the chosen mesh, inversion parameters and regularization adopted, and therefore, a careful and knowledge-based use of the codes is essential. In 2008 and 2011, during two workshops at the Dublin Institute for Advanced Studies over 40 people from academia (scientists and students) and industry from around the world met to discuss 3-D MT inversion. These workshops brought together a mix of code writers as well as code users to assess the current status of 3-D modelling, to compare the results of different codes, and to discuss and think about future improvements and new aims in 3-D modelling. To test the numerical forward solutions, two 3-D models were designed to compare the responses obtained by different codes and/or users. Furthermore, inversion results of these two data sets and two additional data sets obtained from unknown models (secret models) were also compared. In this manuscript the test models and data sets are described (supplementary files are available) and comparisons of the results are shown. Details regarding the used data, forward and inversion parameters as well as computational power are summarized for each case, and the main discussion points of the workshops are reviewed. In general, the responses
Zhang, Haifeng; Zhou, Weiwei; Yang, Yaping; Cheng, Chuanwei
2017-04-01
A novel 3D WO3 /BiVO4 /cobalt phosphate composite inverse opal is designed for photoeletrochemical (PEC) water splitting, yielding a significantly improved PEC performance. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Eng, Z H D; Yick, Y Y; Guo, Y; Xu, H; Reiner, M; Cham, T J; Chen, S H A
2017-09-01
Recognition of faces typically occurs via holistic processing where individual features are combined to provide an overall facial representation. However, when faces are inverted, there is greater reliance on featural processing where faces are recognized based on their individual features. These findings are based on a substantial number of studies using 2-dimensional (2D) faces and it is unknown whether these results can be extended to 3-dimensional (3D) faces, which have more depth information that is absent in the typical 2D stimuli used in face recognition literature. The current study used the face inversion paradigm as a means to investigate how holistic and featural processing are differentially influenced by 2D and 3D faces. Twenty-five participants completed a delayed face-matching task consisting of upright and inverted faces that were presented as both 2D and 3D stereoscopic images. Recognition accuracy was significantly higher for 3D upright faces compared to 2D upright faces, providing support that the enriched visual information in 3D stereoscopic images facilitates holistic processing that is essential for the recognition of upright faces. Typical face inversion effects were also obtained, regardless of whether the faces were presented in 2D or 3D. Moreover, recognition performances for 2D inverted and 3D inverted faces did not differ. Taken together, these results demonstrated that 3D stereoscopic effects influence face recognition during holistic processing but not during featural processing. Our findings therefore provide a novel perspective that furthers our understanding of face recognition mechanisms, shedding light on how the integration of stereoscopic information in 3D faces influences face recognition processes. Copyright © 2017 Elsevier Ltd. All rights reserved.
NASA Astrophysics Data System (ADS)
Luo, H.; Zhang, H.; Gao, J.
2016-12-01
Seismic and magnetotelluric (MT) imaging methods are generally used to characterize subsurface structures at various scales. The two methods are complementary to each other and the integration of them is helpful for more reliably determining the resistivity and velocity models of the target region. Because of the difficulty in finding empirical relationship between resistivity and velocity parameters, Gallardo and Meju [2003] proposed a joint inversion method enforcing resistivity and velocity models consistent in structure, which is realized by minimizing cross gradients between two models. However, it is extremely challenging to combine two different inversion systems together along with the cross gradient constraints. For this reason, Gallardo [2007] proposed a joint inversion scheme that decouples the seismic and MT inversion systems by iteratively performing seismic and MT inversions as well as cross gradient minimization separately. This scheme avoids the complexity of combining two different systems together but it suffers the issue of balancing between data fitting and structure constraint. In this study, we have developed a new joint inversion scheme that avoids the problem encountered by the scheme of Gallardo [2007]. In the new scheme, seismic and MT inversions are still separately performed but the cross gradient minimization is also constrained by model perturbations from separate inversions. In this way, the new scheme still avoids the complexity of combining two different systems together and at the same time the balance between data fitting and structure consistency constraint can be enforced. We have tested our joint inversion algorithm for both 2D and 3D cases. Synthetic tests show that joint inversion better reconstructed the velocity and resistivity models than separate inversions. Compared to separate inversions, joint inversion can remove artifacts in the resistivity model and can improve the resolution for deeper resistivity structures. We
Burgess, Ian B; Aizenberg, Joanna; Lončar, Marko
2013-12-01
Structural hierarchy and complex 3D architecture are characteristics of biological photonic designs that are challenging to reproduce in synthetic materials. Top-down lithography allows for designer patterning of arbitrary shapes, but is largely restricted to planar 2D structures. Self-assembly techniques facilitate easy fabrication of 3D photonic crystals, but controllable defect-integration is difficult. In this paper we combine the advantages of top-down and bottom-up fabrication, developing two techniques to deposit 2D-lithographically-patterned planar layers on top of or in between inverse-opal 3D photonic crystals and creating hierarchical structures that resemble the architecture of the bright green wing scales of the butterfly, Parides sesostris. These fabrication procedures, combining advantages of both top-down and bottom-up fabrication, may prove useful in the development of omnidirectional coloration elements and 3D-2D photonic crystal devices.
A new model of the Arctic crustal thickness from 3D gravity inversion
NASA Astrophysics Data System (ADS)
Lebedeva-Ivanova, N. N.; Gaina, C.; Minakov, A.; Kashubin, S.
2015-12-01
The remarkable increase of new data collections and compilations for the Arctic region during the last decade motivate for a re-evaluation of our knowledge about the crustal structure and the tectonic evolution of the Arctic basins. 3D forward and inverse gravity modelling methods in the spectral domain (Minakov et al. 2012); lithosphere thermal gravity anomaly correction (Alvey et al., 2008); a vertical density variation for the sedimentary layer and lateral crustal variation density are integrated in the algorithm for derive the crustal thickness of the High Arctic region. Recently updated grids of bathymetry (Jakobsson et al., 2012), gravity anomaly (Gaina et al, 2011) and dynamic topography (Spasojevic & Gurnis, 2012) were used as input data for the algorithm. TeMAr sedimentary thickness grid (Petrov et al., 2015) was modified according to the most recent published seismic data, and was re-gridded and utilized as input data. Other input parameters for the algorithm were calibrated using seismic crustal scale profiles. Derived crustal thickness and Moho depth grids cover the area northward from 66° N and fit within a few kilometres with seismic crustal models for the most parts of the High Arctic region. Greater misfit in Moho depth between our results and seismic study (Chain & Lebedeva-Ivanova, 2015) under the northern Canada Basin suggest exceptional property of crust or/and mantel in this part of the Basin. Assumed mantle density of 3.25 kg/cm3provide the best fit for the region; it may indicate pervasive subcontinental lithospheric mantle (Goldstein et al., 2008) under the whole Arctic region. New results show a possible crustal connection between the Alpha and the Lomonosov ridges near the Canadian margin. The deepest Moho depth of c.34 km for Alpha-Mendeleev Ridge System is observed under the southern Mendeleev Ridge. The derived crustal thickness and Moho depth show a substantial improvement from the publicly available grids (CRUST1 (Laske et al., 2013
3D inversion of full gravity gradient tensor data using SL0 sparse recovery
NASA Astrophysics Data System (ADS)
Meng, Zhaohai
2016-04-01
We present a new method dedicated to the interpretation of full gravity gradient tensor data, based on SL0 sparse recovery inversion. The SL0 sparse recovery method aims to find out the minimum value of the objective function to fit the data function and to solve the non-zero solution to the objective function. Based on continuous iteration, we can easily obtain the final global minimum (namely the property and space attribute of the inversion target). We consider which type of tensor data combination produces the best inversion results based on the inversion results of different full gravity gradient tensor data combinations (separate tensor data and combined tensor data). We compare the recovered models obtained by inverting the different combinations of different gravity gradient tensor components to understand how different component combinations contribute to the resolution of the recovered model. Based on the comparison between the SL0 sparse recovery inversion results and the smoothest and focusing inversion results of the full gravity gradient tensor data, we show that SL0 sparse recovery inversion can obtain more stable and efficient inversion results with relatively sharp edge information, and that this method can also produce a stable solution of the inverse problem for complex geological structures. This new method to resolve very large full gravity gradient tensor datasets has the considerable advantage of being highly efficient; the full gravity gradient tensor inversion requires very little time. This new method is very effective in explaining the full gravity tensor which is very sensitive to small changes in local anomaly. The numerical simulation and inversion results of the compositional model indicates that including multiple components for inversion increases the resolution of the recovered density model and improves the structure delineation. We apply our inversion method to invert the gravity gradient tensor survey data from the Vinton salt
NASA Astrophysics Data System (ADS)
Barnoud, Anne; Bouligand, Claire; Coutant, Olivier
2015-04-01
We linearly invert magnetic data for 3D magnetization distribution using a Bayesian methodology with a grid discretization of the space. The Bayesian approach introduces covariance matrices to regularize the ill-posed problem and overcome the non-uniqueness of the solution (Tarantola & Valette, 1982). The use of spatial covariance matrices and grid discretization leads to smooth and compact models. The algorithm provides 3D magnetization models along with resolution parameters extracted from the resolution matrix. The direct computation of the magnetic field includes the surface topography and assumes a linear relationship between rock magnetization and the magnetic field they produce. The methodology is applied to aeromagnetic data from the volcanic island of Basse-Terre in Guadeloupe, Lesser Antilles (Le Borgne & Le Mouël 1976, Le Mouël et al., 1979). Low magnetizations (a few A/m) allow linear inversion that takes into account polarity inversions of the geomagnetic field that occurred across the volcanic history of the island. Inverted magnetizations are consistent with paleomagnetic measurements on surface samples (Carlut et al., 2000 ; Samper et al., 2007). The resulting 3D model is validated against a 2D inversion performed in the Fourier domain (Parker & Huestis, 1974; Bouligand et al., 2014). The 3D distribution of magnetization helps identifying the different volcanic edifices that build the island both at the surface and up to 3 km depth.
NASA Astrophysics Data System (ADS)
Torres-Verdin, C.
2007-05-01
This paper describes the successful implementation of a new 3D AVA stochastic inversion algorithm to quantitatively integrate pre-stack seismic amplitude data and well logs. The stochastic inversion algorithm is used to characterize flow units of a deepwater reservoir located in the central Gulf of Mexico. Conventional fluid/lithology sensitivity analysis indicates that the shale/sand interface represented by the top of the hydrocarbon-bearing turbidite deposits generates typical Class III AVA responses. On the other hand, layer- dependent Biot-Gassmann analysis shows significant sensitivity of the P-wave velocity and density to fluid substitution. Accordingly, AVA stochastic inversion, which combines the advantages of AVA analysis with those of geostatistical inversion, provided quantitative information about the lateral continuity of the turbidite reservoirs based on the interpretation of inverted acoustic properties (P-velocity, S-velocity, density), and lithotype (sand- shale) distributions. The quantitative use of rock/fluid information through AVA seismic amplitude data, coupled with the implementation of co-simulation via lithotype-dependent multidimensional joint probability distributions of acoustic/petrophysical properties, yields accurate 3D models of petrophysical properties such as porosity and permeability. Finally, by fully integrating pre-stack seismic amplitude data and well logs, the vertical resolution of inverted products is higher than that of deterministic inversions methods.
Jia, Jia; Liu, Juan; Jin, Guofan; Wang, Yongtian
2014-09-20
Occlusion culling is an important process that produces correct depth cues for observers in holographic displays, whereas current methods suffer from occlusion errors or high computational loads. We propose a fast and effective method for occlusion culling based on multiple light-point sampling planes and an inverse orthographic projection technique. Multiple light-point sampling planes are employed to remove the hidden surfaces for each direction of the view of the three-dimensional (3D) scene by forward orthographic projection, and the inverse orthographic projection technique is used to determine the effective sampling points of the 3D scene. A numerical simulation and an optical experiment are performed. The results show that this approach can realize accurate occlusion effects, smooth motion parallax, and continuous depth using low angular sampling without any extra computation costs.
NASA Astrophysics Data System (ADS)
Zhu, Lupei; Zhou, Xiaofeng
2016-10-01
Source inversion of small-magnitude events such as aftershocks or mine collapses requires use of relatively high frequency seismic waveforms which are strongly affected by small-scale heterogeneities in the crust. In this study, we developed a new inversion method called gCAP3D for determining general moment tensor of a seismic source using Green's functions of 3D models. It inherits the advantageous features of the "Cut-and-Paste" (CAP) method to break a full seismogram into the Pnl and surface-wave segments and to allow time shift between observed and predicted waveforms. It uses grid search for 5 source parameters (relative strengths of the isotropic and compensated-linear-vector-dipole components and the strike, dip, and rake of the double-couple component) that minimize the waveform misfit. The scalar moment is estimated using the ratio of L2 norms of the data and synthetics. Focal depth can also be determined by repeating the inversion at different depths. We applied gCAP3D to the 2013 Ms 7.0 Lushan earthquake and its aftershocks using a 3D crustal-upper mantle velocity model derived from ambient noise tomography in the region. We first relocated the events using the double-difference method. We then used the finite-differences method and reciprocity principle to calculate Green's functions of the 3D model for 20 permanent broadband seismic stations within 200 km from the source region. We obtained moment tensors of the mainshock and 74 aftershocks ranging from Mw 5.2 to 3.4. The results show that the Lushan earthquake is a reverse faulting at a depth of 13-15 km on a plane dipping 40-47° to N46° W. Most of the aftershocks occurred off the main rupture plane and have similar focal mechanisms to the mainshock's, except in the proximity of the mainshock where the aftershocks' focal mechanisms display some variations.
NASA Astrophysics Data System (ADS)
Zelt, C. A.; Chen, J.; Levander, A.
2016-12-01
In 2012 Rice University carried out a shallow seismic survey in Rifle, Colorado where the groundwater was contaminated by vanadium and uranium ore-processing operations ending in 1958. The purpose of the seismic survey is to provide constraints to improve hydrogeologic modeling. The 3-D P-wave survey over 96 m x 60 m included 2158 shots recorded by 384 channels yielding 828,672 traces. An accelerated weight drop provided data with good signal-to-noise ratio (SNR) and a dominant frequency of 60 Hz. The overall good SNR allows for precise picking and an average uncertainty of 0.65 ms was assigned based on an analysis of all reciprocal time differences. Unreliable source triggering necessitated solving for shot time corrections during travelitme tomography, creating a mixed-parameter inverse problem. Several steps in addition to conventional 3-D traveltime tomography were applied to exploit the dense data and precise picking to overcome the data's low frequency content: (1) stacking the arrival-time-corrected traces in offset bins for 1-D reflectivity modeling to constrain discontinuities; (2) reduced smoothing regularization based on the local angular distribution of raypaths; and (3) a frequency-dependent form of traveltime tomography to account for the data's frequency content. Model assessment techniques include: (1) removal of the best and poorest fit data to assess the effect of outliers, (2) a jackknife procedure to estimate the uncertainty of each velocity node, and (3) checkerboard tests to estimate lateral model resolution using random shot and picking errors consistent with the real data. The results show that most of the velocity model has a relative error of less than 2% and lateral resolution of better than 5, 10 and 20 m to depths of 5, 10 and 20 m, respectively. Results include an isovelocity surface that represents the top of the Wasatch formation.
Realistic 3D coherent transfer function inverse filtering of complex fields.
Cotte, Yann; Toy, Fatih M; Arfire, Cristian; Kou, Shan Shan; Boss, Daniel; Bergoënd, Isabelle; Depeursinge, Christian
2011-08-01
We present a novel technique for three-dimensional (3D) image processing of complex fields. It consists in inverting the coherent image formation by filtering the complex spectrum with a realistic 3D coherent transfer function (CTF) of a high-NA digital holographic microscope. By combining scattering theory and signal processing, the method is demonstrated to yield the reconstruction of a scattering object field. Experimental reconstructions in phase and amplitude are presented under non-design imaging conditions. The suggested technique is best suited for an implementation in high-resolution diffraction tomography based on sample or illumination rotation.
Realistic 3D coherent transfer function inverse filtering of complex fields
Cotte, Yann; Toy, Fatih M.; Arfire, Cristian; Kou, Shan Shan; Boss, Daniel; Bergoënd, Isabelle; Depeursinge, Christian
2011-01-01
We present a novel technique for three-dimensional (3D) image processing of complex fields. It consists in inverting the coherent image formation by filtering the complex spectrum with a realistic 3D coherent transfer function (CTF) of a high-NA digital holographic microscope. By combining scattering theory and signal processing, the method is demonstrated to yield the reconstruction of a scattering object field. Experimental reconstructions in phase and amplitude are presented under non-design imaging conditions. The suggested technique is best suited for an implementation in high-resolution diffraction tomography based on sample or illumination rotation. PMID:21833359
3D Gravity Inversion of Northern Sinai Peninsula: A Case Study
NASA Astrophysics Data System (ADS)
Khalil, Mohamed A.; Santos, Fernando M.
2014-07-01
The Sinai Peninsula has attracted the attention of many geological and geophysical studies as it is influenced and bounded by major tectonic events. Those are (1) the Mesozoic to Early Cenozoic tectonically active opening of the Tethys, (2) the Late Cretaceous to Early Tertiary (Laramide) Syrian arc system, due to closing of the Tethys (3) the Oligo-Miocene Gulf of Suez rifted basin, and (4) the Late Miocene to Recent transform Dead Sea-Gulf of Aqaba rift. Additionally, the shear zones inside Sinai such as the Ragabet El-Naam and Minsherah-Abu Kandu Shear Zones. Each of these major tectonic events has affected dramatically the structure evolution of the northern Sinai area. The present paper estimates the 3D density contrast model using the gravity data of northern Sinai. The estimated 3D density contrast model elucidated the peculiarities of the main structural elements in the region. The estimated 3D density contrast model showed the high and low gravity anomalies that form the main mountains and main valleys in northern Sinai. The estimated low density zones are in agreement with the inferred faults resulting from the first horizontal derivative. Comparing the 3D model with the tectonic history of the region and the results of the first horizontal derivative and least square separation increased the reliability of the model.
Compartmentalization of the Coso East Flank Geothermal Field Imaged by 3-D Full-tensor MT Inversion
NASA Astrophysics Data System (ADS)
Lindsey, Nathaniel J.; Kaven, Joern Ole; Davatzes, Nicholas; Newman, Gregory A.
2016-11-01
Previous magnetotelluric (MT) studies of the high-temperature Coso geothermal system in California identified a subvertical feature of low resistivity (2 - 5 Ohm-m) and appreciable lateral extent (>1 km) in the producing zone of the East Flank field. However, these models could not reproduce gross 3-D effects in the recorded data. We perform 3-D full-tensor inversion and retrieve a resistivity model that out-performs previous 2-D and 3-D off-diagonal models in terms of its fit to the complete 3-D MT dataset as well as the degree of modeling bias. Inclusion of secondary Zxx and Zyy data components leads to a robust east-dip (60o) to the previously identified conductive East Flank reservoir feature, which correlates strongly with recently mapped surface faults, downhole well temperatures, 3-D seismic reflection data, and local microseismicity. We perform synthetic forward modeling to test the best fit dip of this conductor using the response at a nearby MT station. We interpret the dipping conductor as a fractured and fluidized compartment, which is structurally-controlled by an unmapped blind East Flank fault zone.
Compartmentalization of the Coso East Flank geothermal field imaged by 3-D full-tensor MT inversion
NASA Astrophysics Data System (ADS)
Lindsey, Nathaniel J.; Kaven, Joern Ole; Davatzes, Nicholas; Newman, Gregory A.
2017-02-01
Previous magnetotelluric (MT) studies of the high-temperature Coso geothermal system in California identified a subvertical feature of low resistivity (2-5 Ohm m) and appreciable lateral extent (>1 km) in the producing zone of the East Flank field. However, these models could not reproduce gross 3-D effects in the recorded data. We perform 3-D full-tensor inversion and retrieve a resistivity model that out-performs previous 2-D and 3-D off-diagonal models in terms of its fit to the complete 3-D MT data set as well as the degree of modelling bias. Inclusion of secondary Zxx and Zyy data components leads to a robust east-dip (60†) to the previously identified conductive East Flank reservoir feature, which correlates strongly with recently mapped surface faults, downhole well temperatures, 3-D seismic reflection data, and local microseismicity. We perform synthetic forward modelling to test the best-fit dip of this conductor using the response at a nearby MT station. We interpret the dipping conductor as a fractured and fluidized compartment, which is structurally controlled by an unmapped blind East Flank fault zone.
Extrapolated Tikhonov method and inversion of 3D density images of gravity data
NASA Astrophysics Data System (ADS)
Wang, Zhu-Wen; Xu, Shi; Liu, Yin-Ping; Liu, Jing-Hua
2014-06-01
Tikhonov regularization (TR) method has played a very important role in the gravity data and magnetic data process. In this paper, the Tikhonov regularization method with respect to the inversion of gravity data is discussed. and the extrapolated TR method (EXTR) is introduced to improve the fitting error. Furthermore, the effect of the parameters in the EXTR method on the fitting error, number of iterations, and inversion results are discussed in details. The computation results using a synthetic model with the same and different densities indicated that. compared with the TR method, the EXTR method not only achieves the a priori fitting error level set by the interpreter but also increases the fitting precision, although it increases the computation time and number of iterations. And the EXTR inversion results are more compact than the TR inversion results, which are more divergent. The range of the inversion data is closer to the default range of the model parameters, and the model features and default model density distribution agree well.
NASA Astrophysics Data System (ADS)
Yang, Dikun; Oldenburg, Douglas W.
2017-01-01
The Lalor deposit is a massive sulphide that is characterised as a stack of conductive ore lenses buried more than 600 m deep. We invert helicopter sub-audio magnetics (HeliSAM) data from Lalor collected using a ground large transmitter loop and an airborne total magnetic intensity (TMI) magnetometer measuring the time-domain electromagnetic (EM) responses. The TMI data are modelled as a projection of the anomalous field onto the earth's magnetic field. Inversion of these data is considered a significant case study because of two challenges. First, the early-time data are contaminated by the infrastructure on the surface. Second, inverting the data with a uniform half-space as the initial model results in a mathematically acceptable, but non-geologic, model. We create workflows to overcome these difficulties. For the contaminated data, we use a locally refined mesh and a constrained inversion to recover highly conductive cells near the surface that effectively represent the infrastructure. This allows us to safely extract geologic information from the early time data. The non-uniqueness in the inversion is reduced by warm-starting the voxel 3D inversion with a more reasonable initial guess, for example, a block model from geometric inversions. Those procedures greatly improve the inversion image from the surface to the bottom of the target at Lalor, and they can easily be incorporated into the industrial production workflows.
3D Magnetization Vector Inversion of Magnetic Data: Improving and Comparing Methods
NASA Astrophysics Data System (ADS)
Liu, Shuang; Hu, Xiangyun; Zhang, Henglei; Geng, Meixia; Zuo, Boxin
2017-09-01
Magnetization vector inversion is an useful approach to invert for magnetic anomaly in the presence of significant remanent magnetization and self-demagnetization. However, magnetizations are usually obtained in many different directions under the influences of geophysical non-uniqueness. We propose an iteration algorithm of magnetization vector inversion (M-IDI) that one couple of magnetization direction is iteratively computed after the magnetization intensity is recovered from the magnitude magnetic anomaly. And we compare it with previous methods of (1) three orthogonal components inversion of total magnetization vector at Cartesian framework (MMM), (2) intensity, inclination and declination inversion at spherical framework (MID), (3) directly recovering the magnetization inclination and declination (M-IDCG) and (4) estimating the magnetization direction using correlation method (M-IDC) at the sequential inversion frameworks. The synthetic examples indicate that MMM returns multiply magnetization directions and MID results are strongly dependent on initial model and parameter weights. M-IDI computes faster than M-IDC and achieves a constant magnetization direction compared with M-IDCG. Additional priori information constraints can improve the results of MMM, MID and M-IDCG. Obtaining one magnetization direction, M-IDC and M-IDI are suitable for single and isolated anomaly. Finally, M-IDI and M-IDC are used to invert and interpret the magnetic anomaly of the Galinge iron-ore deposit (NW China) and the results are verified by information from drillholes and physical properties measurements of ore and rock samples. Magnetization vector inversion provides a comprehensive way to evaluate and investigate the remanent magnetization and self-demagnetization.
NASA Astrophysics Data System (ADS)
Sladen, A.; Monteiller, V.
2014-12-01
Most large earthquakes are generated in subduction zones. To study the complexity of these events, teleseismic body waves offer many advantages over other types of data: they allow to study both the temporal and spatial evolution of slip during the rupture, they don't depend on the presence of nearby land and they allow to study earthquakes regardless of their location. Since the development of teleseismic finite-fault inversion in the 1980th, teleseismic body waves have been simulated using 1D velocity models to take into account propagation effects at the source. Yet, subduction zones are known to be highly heterogeneous: they are characterized by curved and dipping structures, strong seismic velocity contrasts, strong variations of topography and height of the water column. The main reason for relying on a 1D approximation is the computational cost of 3D simulations. And while forward simulations of teleseismic waves in a 3D Earth are only starting to be tractable on modern computers at the frequency range of interest (0.1Hz or shorter), finite-fault source studies require a large number of these simulations. In this work, we present a new and efficient approach to compute 3D teleseismic body waves, in which the full 3D propagation is only computed in a regional domain using discontinuous Galerkin finite-element method, while the rest of the seismic wave field is propagated in a background axisymmetric Earth. The regional and global wave fields are matched using the so-called Total-Field/Scattered-Field technique. This new simulation approach allows us to study the waveform complexities resulting from 3D propagation and investigate how they could improve the resolution and reduce the non-uniqueness of finite-fault inversions.
Electromagnetic Response Inversion for a 3D Distribution of Conductivity/Dielect
Newman, Gregory
2001-10-24
NLCGCS inverts electromagnetic responses for a 3D distribution of electrical conductivity and dielectric permittivity within the earth for geophysical applications using single processor computers. The software comes bundled with a graphical user interface to aid in model construction and analysis and viewing of earth images. The solution employs both dipole and finite size source configurations for harmonic oscillatory sources. A new nonlinear preconditioner is included in the solution to speed up solution convergence.
NASA Astrophysics Data System (ADS)
Santhanam, Anand P.; Min, Yugang; Mudur, Sudhir P.; Rastogi, Abhinav; Ruddy, Bari H.; Shah, Amish; Divo, Eduardo; Kassab, Alain; Rolland, Jannick P.; Kupelian, Patrick
2010-07-01
A method to estimate the deformation operator for the 3D volumetric lung dynamics of human subjects is described in this paper. For known values of air flow and volumetric displacement, the deformation operator and subsequently the elastic properties of the lung are estimated in terms of a Green's function. A Hyper-Spherical Harmonic (HSH) transformation is employed to compute the deformation operator. The hyper-spherical coordinate transformation method discussed in this paper facilitates accounting for the heterogeneity of the deformation operator using a finite number of frequency coefficients. Spirometry measurements are used to provide values for the airflow inside the lung. Using a 3D optical flow-based method, the 3D volumetric displacement of the left and right lungs, which represents the local anatomy and deformation of a human subject, was estimated from 4D-CT dataset. Results from an implementation of the method show the estimation of the deformation operator for the left and right lungs of a human subject with non-small cell lung cancer. Validation of the proposed method shows that we can estimate the Young's modulus of each voxel within a 2% error level.
Structural results for La Palma island using 3-D gravity inversion
NASA Astrophysics Data System (ADS)
Camacho, A. G.; FernáNdez, J.; GonzáLez, P. J.; Rundle, J. B.; Prieto, J. F.; Arjona, A.
2009-05-01
A recent gravity survey composed of 317 bench marks all over the island of La Palma (Canary Islands) is used, in combination with satellite data for regional aspects, to obtain results about structural properties of the island connected with the tectonic environment and local volcanism. To that end, a nonlinear three-dimensional gravity inversion approach is considered. The inversion scheme provides, in a nonsubjective form, the geometry of the anomalous bodies constructed in a random growth process. Results from the inversion can be interpreted in the framework of the geologic evolution of this ocean island volcano as a complex composite volcano with a large central body with high-density corresponding to the older intrusive part of the basalt complex. New unexpected features are enlightened, such as large thermal anomalies in the upper mantle southward of La Palma, as well as fracture en echelon zones associable to a slow active process of dislocation related to the recent volcanism in the southern half of the island. The results obtained for La Palma as a test site testify to the usefulness of the developed gravity inversion methodology for structural studies on islands in general.
NASA Astrophysics Data System (ADS)
Richardson, Mark; Davenport, Ian; Gurney, Robert
2014-05-01
Snow provides large seasonal storage of freshwater, and information about the distribution of snow mass as snow water equivalent (SWE) is important for hydrological planning and detecting climate change impacts. Large regional disagreements remain between estimates from reanalyses, remote sensing and modelling. Assimilating passive microwave information improves SWE estimates in many regions, but the assimilation must account for how microwave scattering depends on snow stratigraphy. Physical snow models can estimate snow stratigraphy, but users must consider the computational expense of model complexity versus acceptable errors. Using data from the National Aeronautics and Space Administration Cold Land Processes Experiment and the Helsinki University of Technology microwave emission model of layered snowpacks, it is shown that simulations of the brightness temperature difference between 19 and 37 GHz vertically polarised microwaves are consistent with advanced microwave scanning radiometer-earth observing system and special sensor microwave imager retrievals once known stratigraphic information is used. Simulated brightness temperature differences for an individual snow profile depend on the provided stratigraphic detail. Relative to a profile defined at the 10-cm resolution of density and temperature measurements, the error introduced by simplification to a single layer of average properties increases approximately linearly with snow mass. If this brightness temperature error is converted into SWE using a traditional retrieval method, then it is equivalent to ±13 mm SWE (7 % of total) at a depth of 100 cm. This error is reduced to ±5.6 mm SWE (3 % of total) for a two-layer model.
2D and 3D separate and joint inversion of airborne ZTEM and ground AMT data: Synthetic model studies
NASA Astrophysics Data System (ADS)
Sasaki, Yutaka; Yi, Myeong-Jong; Choi, Jihyang
2014-05-01
The ZTEM (Z-axis Tipper Electromagnetic) method measures naturally occurring audio-frequency magnetic fields and obtains the tipper function that defines the relationship among the three components of the magnetic field. Since the anomalous tipper responses are caused by the presence of lateral resistivity variations, the ZTEM survey is most suited for detecting and delineating conductive bodies extending to considerable depths, such as graphitic dykes encountered in the exploration of unconformity type uranium deposit. Our simulations shows that inversion of ZTEM data can detect reasonably well multiple conductive dykes placed 1 km apart. One important issue regarding ZTEM inversion is the effect of the initial model, because homogeneous half-space and (1D) layered structures produce no responses. For the 2D model with multiple conductive dykes, the inversion results were useful for locating the dykes even when the initial model was not close to the true background resistivity. For general 3D structures, however, the resolution of the conductive bodies can be reduced considerably depending on the initial model. This is because the tipper magnitudes from 3D conductors are smaller due to boundary charges than the 2D responses. To alleviate this disadvantage of ZTEM surveys, we combined ZTEM and audio-frequency magnetotelluric (AMT) data. Inversion of sparse AMT data was shown to be effective in providing a good initial model for ZTEM inversion. Moreover, simultaneously inverting both data sets led to better results than the sequential approach by enabling to identify structural features that were difficult to resolve from the individual data sets.
3-D Sound Propagation and Acoustic Inversions in Shallow Water Oceans
2012-12-19
models provide a physical insight into this shadowing effect (see Figure 8). In addition, the model suggests that 3-D sound focusing due to the canyon...Ocean. Eng., vol. 35, pp. 710-721. [published, refereed] 2010 J.F. Lynch, Y.-T. Lin, T.F. Duda, and A.E. Newhall, "Acoustic Ducting, Shadowing ...fixed arc-length grid.] 10 Modeling comparisons Propagate over seamount , off center Source at 250 m, 100Hz 4 cases - (1) Nx2D, (2) Cartesian, (3
NASA Astrophysics Data System (ADS)
Timur, Emre
2016-04-01
There are numerous geophysical methods used to investigate geothermal areas. The major purpose of this magnetic survey is to locate the boudaries of active hydrothermal system in the South of Gediz Graben in Salihli (Manisa/Turkey). The presence of the hydrothermal system had already been inferred from surface evidence of hydrothermal activity and drillings. Firstly, 3-D prismatic models were theoretically investigated and edge detection methods were utilized with an iterative inversion method to define the boundaries and the parameters of the structure. In the first step of the application, it was necessary to convert the total field anomaly into a pseudo-gravity anomaly map. Then the geometric boudaries of the structures were determined by applying a MATLAB based software with 3 different edge detection algorithms. The exact location of the structures were obtained by using these boundary coordinates as initial geometric parameters in the inversion process. In addition to these methods, reduction to pole and horizontal gradient methods were applied to the data to achieve more information about the location and shape of the possible reservoir. As a result, the edge detection methods were found to be successful, both in the field and as theoretical data sets for delineating the boundaries of the possible geothermal reservoir structure. The depth of the geothermal reservoir was determined as 2,4 km from 3-D inversion and 2,1 km from power spectrum methods.
NASA Astrophysics Data System (ADS)
Hara, Tatsuhiko
2004-08-01
We implement the Direct Solution Method (DSM) on a vector-parallel supercomputer and show that it is possible to significantly improve its computational efficiency through parallel computing. We apply the parallel DSM calculation to waveform inversion of long period (250-500 s) surface wave data for three-dimensional (3-D) S-wave velocity structure in the upper and uppermost lower mantle. We use a spherical harmonic expansion to represent lateral variation with the maximum angular degree 16. We find significant low velocities under south Pacific hot spots in the transition zone. This is consistent with other seismological studies conducted in the Superplume project, which suggests deep roots of these hot spots. We also perform simultaneous waveform inversion for 3-D S-wave velocity and Q structure. Since resolution for Q is not good, we develop a new technique in which power spectra are used as data for inversion. We find good correlation between long wavelength patterns of Vs and Q in the transition zone such as high Vs and high Q under the western Pacific.
Development of direct-inverse 3-D methods for applied transonic aerodynamic wing design and analysis
NASA Technical Reports Server (NTRS)
Carlson, Leland A.
1989-01-01
An inverse wing design method was developed around an existing transonic wing analysis code. The original analysis code, TAWFIVE, has as its core the numerical potential flow solver, FLO30, developed by Jameson and Caughey. Features of the analysis code include a finite-volume formulation; wing and fuselage fitted, curvilinear grid mesh; and a viscous boundary layer correction that also accounts for viscous wake thickness and curvature. The development of the inverse methods as an extension of previous methods existing for design in Cartesian coordinates is presented. Results are shown for inviscid wing design cases in super-critical flow regimes. The test cases selected also demonstrate the versatility of the design method in designing an entire wing or discontinuous sections of a wing.
Development and Tuning of a 3-D Stochastic Inversion Methodology for the European Arctic
2008-09-01
west of the (most likely) Late Triassic-Early Jurassic Novaya Zemlya Fold Belt. The nature of the underlying crystalline crust and upper mantle in...10 and 150 s period were combined with existing data provided by the University of Colorado at Boulder. This new data set was inverted for maps...showing the 2D group-velocity distribution of Love and Rayleigh waves for specific periods . Using a Monte Carlo inversion technique (Shapiro and
NASA Astrophysics Data System (ADS)
Torne, Montserrat; Zeyen, Hermann; Jimenez-Munt, Ivone; Fernandez, Manel; Vergés, Jaume
2017-04-01
We investigate the lithospheric density structure of the Iberian Peninsula and the surrounding Atlantic and Mediterranean margins from a 3D joint inversion of free-air, geoid and elevation data, based on a Bayesian approach. In addition, the crustal structure has been further constrained by incorporating about 750 Moho values from DSS investigations and RF analysis covering the entire region. Our preliminary results shows a significant lithospheric deformation along the plate boundaries, the Bay of Biscay-Pyrenees to the North and the Azores-Gibraltar to the south, where the CMB and LAB are located at depths more than 45 and 150 km, respectively. Noteworthy is the arcuate lithospheric thickening located at the westernmost end of the Gibraltar Arc system showing the presence of the NW-to-Westward retreated Gibraltar Arc slab that has given rise to the formation of the Betics-Rif Alpine belt system and the back arc Alboran basin. To the west, the stable-slightly deformed Iberian massif shows a quasi-flat CMB and LAB topography (30 to 32 km and about 110 km, respectively). The crust and mantle lithosphere thin towards the Mediterranean and Atlantic margins, with the exception of its northern margin where lithospheric thickening extends offshore to the Gulf of Biscay. In the western Mediterranean the SE-Neogene slab retreat has resulted in a significant thinning of the crust and mantle lithosphere. Thin lithosphere is also observed in the Tagus-Horseshoe abyssal plain region where the LAB shallows to less than 90 km. This work has been funded by the Spanish projects MITE (CGL2014-59516-P) and WEME-CSIC project 201330E11.
Optimization of computations for adjoint field and Jacobian needed in 3D CSEM inversion
NASA Astrophysics Data System (ADS)
Dehiya, Rahul; Singh, Arun; Gupta, Pravin K.; Israil, M.
2017-01-01
We present the features and results of a newly developed code, based on Gauss-Newton optimization technique, for solving three-dimensional Controlled-Source Electromagnetic inverse problem. In this code a special emphasis has been put on representing the operations by block matrices for conjugate gradient iteration. We show how in the computation of Jacobian, the matrix formed by differentiation of system matrix can be made independent of frequency to optimize the operations at conjugate gradient step. The coarse level parallel computing, using OpenMP framework, is used primarily due to its simplicity in implementation and accessibility of shared memory multi-core computing machine to almost anyone. We demonstrate how the coarseness of modeling grid in comparison to source (comp`utational receivers) spacing can be exploited for efficient computing, without compromising the quality of the inverted model, by reducing the number of adjoint calls. It is also demonstrated that the adjoint field can even be computed on a grid coarser than the modeling grid without affecting the inversion outcome. These observations were reconfirmed using an experiment design where the deviation of source from straight tow line is considered. Finally, a real field data inversion experiment is presented to demonstrate robustness of the code.
NASA Astrophysics Data System (ADS)
Ekinci, Yunus Levent; Ertekin, Can
2015-04-01
Concern about sedimentary basins is generally related to their genetic and economic significance. Analysis of sedimentary basins requires the acquisition of data through outcrop studies and subsurface investigations that encompass drilling and geophysics. These data are commonly analysed by computer-assisted techniques. One of these methods is based on analysing gravity anomalies to compute the depth of sedimentary basin-basement rock interface. Sedimentary basins produce negative gravity anomalies, because they have mostly lower densities than that of the surrounding basement rocks. Density variations in a sedimentary fill increase rapidly at shallower depths then gradually reach the density of surrounding basement rocks due to the geostatic pressure i.e. compaction. The decrease of the density contrast can be easily estimated by a quadratic function. Hence, if the densities are chosen properly and the regional background is removed correctly, the topographical relief of the sedimentary basin-basement rock interface might be estimated by the inversion of the gravity data using an exponential density-depth relation. Three dimensional forward modelling procedure can be carried out by introducing a Cartesian coordinate system, and placing vertical prisms just below observation points on the grid plane. Depth to the basement, namely depths to the bottom of the vertical prisms are adjusted in an iterative manner by minimizing the differences between measured and calculated residual gravity anomalies. In this study, we present a MATLAB-based inversion code for the interpretation of sedimentary basins by approximating the topographical relief of sedimentary basin-basement rock interfaces. For a given gridded residual gravity anomaly map, the procedure estimates the bottom depths of vertical prisms by considering some published formulas and assumptions. The utility of the developed inversion code was successfully tested on theoretically produced gridded gravity data set
Focus measurement in 3D focal stack using direct and inverse discrete radon transform
NASA Astrophysics Data System (ADS)
Gómez-Cárdenes, Óscar; Marichal-Hernández, José G.; Trujillo-Sevilla, Juan M.; Carmona-Ballester, David; Rodríguez-Ramos, José M.
2017-05-01
The discrete Radon transform, DRT, calculates, with linearithmic complexity, the sum of pixels through a set of discrete lines covering all possible slopes and intercepts in an image. In 2006, a method was proposed to compute the inverse DRT that remains exact and fast, in spite of being iterative. In this work the DRT pair is used to propose a Ridgelet and a Curvelet transform that perform focus measurement of an image. Then the shape from focus approach based on DRT pair is applied to a focal stack to create a depth map of a scene.
Aydmer, A.A.; Chew, W.C.; Cui, T.J.; Wright, D.L.; Smith, D.V.; Abraham, J.D.
2001-01-01
A simple and efficient method for large scale three-dimensional (3-D) subsurface imaging of inhomogeneous background is presented. One-dimensional (1-D) multifrequency distorted Born iterative method (DBIM) is employed in the inversion. Simulation results utilizing synthetic scattering data are given. Calibration of the very early time electromagnetic (VETEM) experimental waveforms is detailed along with major problems encountered in practice and their solutions. This discussion is followed by the results of a large scale application of the method to the experimental data provided by the VETEM system of the U.S. Geological Survey. The method is shown to have a computational complexity that is promising for on-site inversion.
A numerical method for the inverse problem of cell traction in 3D
NASA Astrophysics Data System (ADS)
Vitale, G.; Preziosi, L.; Ambrosi, D.
2012-09-01
Force traction microscopy is an inversion method that allows us to obtain the stress field applied by a living cell on the environment on the basis of a pointwise knowledge of the displacement produced by the cell itself. This classical biophysical problem, usually addressed in terms of Green’s functions, can be alternatively tackled in a variational framework. In such a case, a variation of the error functional under suitable regularization is operated in view of its minimization. This setting naturally suggests the introduction of a new equation, based on the adjoint operator of the elasticity problem. In this paper, we illustrate a numerical strategy of the inversion method that discretizes the partial differential equations associated with the optimal control problem by finite elements. A detailed discussion of the numerical approximation of a test problem (with known solution) that contains most of the mathematical difficulties of the real one allows a precise evaluation of the degree of confidence that one can achieve in the numerical results.
Dirac Circles and Quantum Hall Effect in 3D Inversion-Symmetric Crystals
NASA Astrophysics Data System (ADS)
Wieder, Benjamin J.; Kim, Youngkuk; Kane, C. L.
2015-03-01
In the presence of inversion and time-reversal symmetries, materials with weak spin-orbit coupling may host topologically protected Dirac line nodes. A band inversion transition in these systems can produce a line node which closes on itself and forms a protected Dirac circle. The surfaces parallel to this circle host zero-energy puddles in momentum space which are flat if the inverting bands have the same effective mass. In cases with differing effective masses, the surface modes disperse, but the bulk Dirac circle remains gapless. Adding an external magnetic field perpendicular to this circle creates surface Landau levels, whose number can be controlled by tuning the field strength. When a new level is created or destroyed, the bulk becomes gapless and the zero-temperature bulk conductivity displays a sharp peak. The sequence of conductivity peaks describes an unusual manifestation of the integer quantum hall effect. We characterize surface and bulk transport as a function of magnetic field strength and in the presence of disorder.
Bhattacharya, Jishnu; Wolverton, C
2013-05-07
Spinel oxides represent an important class of cathode materials for Li-ion batteries. Two major variants of the spinel crystal structure are normal and inverse. The relative stability of normal and inverse ordering at different stages of lithiation has important consequences in lithium diffusivity, voltage, capacity retention and battery life. In this paper, we investigate the relative structural stability of normal and inverse structures of the 3d transition metal oxide spinels with first-principles DFT calculations. We have considered ternary spinel oxides LixM2O4 with M = Ti, V, Cr, Mn, Fe, Co and Ni in both lithiated (x = 1) and delithiated (x = 0) conditions. We find that for all lithiated spinels, the normal structure is preferred regardless of the metal. We observe that the normal structure for all these oxides has a lower size mismatch between octahedral cations compared to the inverse structure. With delithiation, many of the oxides undergo a change in stability with vanadium in particular, showing a tendency to occupy tetrahedral sites. We find that in the delithiated oxide, only vanadium ions can access a +5 oxidation state which prefers tetrahedral coordination. We have also calculated the average voltage of lithiation for these spinels. The calculated voltages agree well with the previously measured and calculated values, wherever available. For the yet to be characterized spinels, our calculation provides voltage values which can motivate further experimental attention. Lastly, we observe that all the normal spinel oxides of the 3d transition metal series have a driving force for a transformation to the non-spinel structure upon delithiation.
Hall-Effect Sign Inversion in a Realizable 3D Metamaterial
NASA Astrophysics Data System (ADS)
Kadic, Muamer; Schittny, Robert; Bückmann, Tiemo; Kern, Christian; Wegener, Martin
2015-04-01
In 2009, Briane and Milton proved mathematically the existence of three-dimensional isotropic metamaterials with a classical Hall coefficient that is negative with respect to that of all of the metamaterial constituents. Here, we significantly simplify their blueprint towards an architecture composed of only a single-constituent material in vacuum or air, which can be seen as a special type of porosity. We show numerically that the sign of the Hall voltage is determined by a separation parameter between adjacent tori. This qualitative behavior is robust even for only a small number of metamaterial unit cells. The combination of simplification and robustness brings experimental verification of this striking sign inversion into reach. Furthermore, we provide a simple intuitive explanation of the underlying physical mechanism.
Development of direct-inverse 3-D methods for applied transonic aerodynamic wing design and analysis
NASA Technical Reports Server (NTRS)
Carlson, Leland A.
1989-01-01
Progress in the direct-inverse wing design method in curvilinear coordinates has been made. This includes the remedying of a spanwise oscillation problem and the assessment of grid skewness, viscous interaction, and the initial airfoil section on the final design. It was found that, in response to the spanwise oscillation problem that designing at every other spanwise station produced the best results for the cases presented, a smoothly varying grid is especially needed for the accurate design at the wing tip, the boundary layer displacement thicknesses must be included in a successful wing design, the design of high and medium aspect ratio wings is possible with this code, and the final airfoil section designed is fairly independent of the initial section.
Barlebo, H.C.; Rosbjerg, D.; Hill, M.C.
1996-01-01
An extensive amount of data including hydraulic heads, hydraulic conductivities and concentrations of several solutes from controlled injections have been collected during the MADE 1 and MADE 2 experiments at a heterogeneous site near Columbus, Mississippi. In this paper the use of three-dimensional inverse groundwater models including simultaneous estimation of flow and transport parameters is proposed to help identify the dominant characteristics at the site. Simulations show that using a hydraulic conductivity distribution obtained from 2187 borehole flowmeter tests directly in the model produces poor matches to the measured hydraulic heads and tritium concentrations. Alternatively, time averaged hydraulic head maps are used to define zones of constant hydraulic conductivity to be estimated. Preliminary simulations suggest that in the case of conservative transport many, but not all, of the major plume characteristics can be explained by large-scale heterogeneity in recharge and hydraulic conductivity.
Brosten, T.R.; Day-Lewis, F. D.; Schultz, G.M.; Curtis, G.P.; Lane, J.W.
2011-01-01
Electromagnetic induction (EMI) instruments provide rapid, noninvasive, and spatially dense data for characterization of soil and groundwater properties. Data from multi-frequency EMI tools can be inverted to provide quantitative electrical conductivity estimates as a function of depth. In this study, multi-frequency EMI data collected across an abandoned uranium mill site near Naturita, Colorado, USA, are inverted to produce vertical distribution of electrical conductivity (EC) across the site. The relation between measured apparent electrical conductivity (ECa) and hydraulic conductivity (K) is weak (correlation coefficient of 0.20), whereas the correlation between the depth dependent EC obtained from the inversions, and K is sufficiently strong to be used for hydrologic estimation (correlation coefficient of -0.62). Depth-specific EC values were correlated with co-located K measurements to develop a site-specific ln(EC)-ln(K) relation. This petrophysical relation was applied to produce a spatially detailed map of K across the study area. A synthetic example based on ECa values at the site was used to assess model resolution and correlation loss given variations in depth and/or measurement error. Results from synthetic modeling indicate that optimum correlation with K occurs at ~0.5m followed by a gradual correlation loss of 90% at 2.3m. These results are consistent with an analysis of depth of investigation (DOI) given the range of frequencies, transmitter-receiver separation, and measurement errors for the field data. DOIs were estimated at 2.0??0.5m depending on the soil conductivities. A 4-layer model, with varying thicknesses, was used to invert the ECa to maximize available information within the aquifer region for improved correlations with K. Results show improved correlation between K and the corresponding inverted EC at similar depths, underscoring the importance of inversion in using multi-frequency EMI data for hydrologic estimation. ?? 2011.
Stratigraphic and metamorphic inversions in the central Menderes Massif: a new structural model
NASA Astrophysics Data System (ADS)
Okay, Aral I.
2001-04-01
The Menderes Massif is a large area of dominantly Tertiary metamorphic rocks in western Turkey. It is bordered in the west by the Cycladic Metamorphic Complex with Eocene high-pressure/low-temperature (HP/LT) metamorphism. In the Central Menderes the Aydın mountains are made up of a thrust stack of Eocene age. At the base of the thrust stack, greenschist-facies Paleozoic metasediments of the Menderes Massif form an inverted stratigraphic sequence. The Barrovian-type metamorphism is also inverted with garnet-bearing metapelites lying over the lower-grade biotite-bearing metapelites. The P-T conditions in the garnet zone are estimated as 530°C and 8 kbar. This schist sequence of the central Menderes Massif is interpreted as the inverted lower limb of a major southward closing recumbent fold, with the southern Menderes Massif representing a section from the near hinge of this fold. The Paleozoic metamorphic rocks of the central Menderes Massif are tectonically overlain by gneiss klippen possibly originating from the sheared and southward translated core of the Menderes fold. Lying also tectonically over the Paleozoic metamorphic rocks is a major thrust sheet belonging to the Cycladic metamorphic complex. It consists of garnet micaschist, Mesozoic marble, serpentinite and amphibolitised eclogite. Although it has a highly sheared internal structure, it probably represents an initially coherent sequence that has undergone HP/LT metamorphism during the Eocene. The Aydın mountains are dominated by contractional structures with subordinate extensional structures.
NASA Astrophysics Data System (ADS)
Balkaya, Çağlayan; Ekinci, Yunus Levent; Göktürkler, Gökhan; Turan, Seçil
2017-01-01
3D non-linear inversion of total field magnetic anomalies caused by vertical-sided prismatic bodies has been achieved by differential evolution (DE), which is one of the population-based evolutionary algorithms. We have demonstrated the efficiency of the algorithm on both synthetic and field magnetic anomalies by estimating horizontal distances from the origin in both north and east directions, depths to the top and bottom of the bodies, inclination and declination angles of the magnetization, and intensity of magnetization of the causative bodies. In the synthetic anomaly case, we have considered both noise-free and noisy data sets due to two vertical-sided prismatic bodies in a non-magnetic medium. For the field case, airborne magnetic anomalies originated from intrusive granitoids at the eastern part of the Biga Peninsula (NW Turkey) which is composed of various kinds of sedimentary, metamorphic and igneous rocks, have been inverted and interpreted. Since the granitoids are the outcropped rocks in the field, the estimations for the top depths of two prisms representing the magnetic bodies were excluded during inversion studies. Estimated bottom depths are in good agreement with the ones obtained by a different approach based on 3D modelling of pseudogravity anomalies. Accuracy of the estimated parameters from both cases has been also investigated via probability density functions. Based on the tests in the present study, it can be concluded that DE is a useful tool for the parameter estimation of source bodies using magnetic anomalies.
Enhanced imaging of CO2 at the Ketzin storage site: Inversion of 3D time-lapse seismic data
NASA Astrophysics Data System (ADS)
Gil, M.; Götz, J.; Ivanova, A.; Juhlin, C.; Krawczyk, C. M.; Lüth, S.; Yang, C.
2012-04-01
The Ketzin test site, located near Berlin, is Europe's longest-operating on-shore CO2 storage site. As of December 2011, more than 56,000 tons of food grade CO2 has been injected since June 2008 in an anticlinal structure of the Northeast German Basin. The target reservoir consists of porous, brine bearing sandstone units of the Upper Triassic Stuttgart Formation at approximately 630 to 650 m depth. In order to enhance the understanding of the structural geometry of the site and to investigate the extension of the CO2-plume, several geophysical monitoring methods are being applied at Ketzin, among these are active seismic measurements, geoelectrics and borehole measurements. Among the various seismic techniques (e.g. 2D reflection surveys, crosshole tomography, Vertical Seismic Profiling, 2D- and 3D-Moving Source Profiling) employed at this pilot site, 3D time-lapse reflection surveys are an important component. The baseline 3D survey was acquired in 2005 and the first repeat measurements were performed in 2009 after injection of about 22,000 tons of CO2. The second repeat survey is planned to be carried out in fall 2012. These measurements allow the time-lapse signature of the injected CO2 to be imaged. The time-lapse amplitude variation attributed to the injected CO2 in the reservoir matches, considering detection limits of seismic surface measurements, the expected distribution of the CO2 plume derived from reservoir simulations. Previous attempts towards a quantitative interpretation were based on integrative considerations of different types of geophysical measurements using strict assumptions and characterized by large error bars. In order to increase the resolution and reliability of the data and to improve estimation of rock properties and especially to enhance the imaging resolution of the CO2-plume, the time-lapse 3D seismic data have now been inverted for seismic impedances with different methods, which is the focus of this presentation. One difficulty
NASA Astrophysics Data System (ADS)
Mair, H. D.; Ciorau, P.; Owen, D.; Hazelton, T.; Dunning, G.
2000-05-01
Two ultrasonic simulation packages: Imagine 3D and SIMSCAN have specifically been developed to solve the inverse problem for blade root and rotor steeple of low-pressure turbine. The software was integrated with the 3D drawing of the inspected parts, and with the dimensions of linear phased-array probes. SIMSCAN simulates the inspection scenario in both optional conditions: defect location and probe movement/refracted angle range. The results are displayed into Imagine 3-D, with a variety of options: rendering, display 1:1, grid, generated UT beam. The results are very useful for procedure developer, training and to optimize the phased-array probe inspection sequence. A spreadsheet is generated to correlate the defect coordinates with UT data (probe position, skew and refracted angle, UT path, and probe movement). The simulation models were validated during experimental work with phased-array systems. The accuracy in probe position is ±1 mm, and the refracted/skew angle is within ±0.5°. Representative examples of phased array focal laws/probe movement for a specific defect location, are also included.
Gas Sensor Based on 3-D WO3 Inverse Opal: Design and Applications
Xing, Ruiqing; Du, Yang; Zhao, Xiaonan; Zhang, Xiu
2017-01-01
A three-dimensional inverse opal (3DIO) WO3 architecture has been synthesized via a simple sacrificial template method. Morphology features of the 3DIO were characterized by scanning electron microscope (SEM) and its structure was characterized by X-ray diffraction (XRD). The shrinking ratio of the PMMA spheres was ~28.2% through measuring the distribution of the PMMA spheres and 3DIO WO3 center-to-center distance between the spheres and macropores, respectively. Beyond that, the 3DIO gas sensing properties were investigated systematically and the sensing mechanism of 3DIO WO3 was proposed. The results indicated that the response of the 3DIO sensor possessed excellent sensitivity to acetone gas, especially at trace levels. The 3DIO gas sensor response was ~7 to 5 ppm of acetone and could detect acetone low to 0.2 ppm effectively, which was in close proximity to the theoretical low detection limit of 0.14 ppm when Ra/Rg ≥ 1.2 was used as the criterion for reliable gas sensing. All in all, the obvious satisfaction of the gas-sensing properties was ascribed to the structure of the 3DIO, and the sensor could be a promising novel device in the future. PMID:28353672
NASA Astrophysics Data System (ADS)
Oh, Ju-Won; Alkhalifah, Tariq
2016-09-01
Multiparameter full waveform inversion (FWI) applied to an elastic orthorhombic model description of the subsurface requires in theory a nine-parameter representation of each pixel of the model. Even with optimal acquisition on the Earth surface that includes large offsets, full azimuth, and multicomponent sensors, the potential for trade-off between the elastic orthorhombic parameters are large. The first step to understanding such trade-off is analysing the scattering potential of each parameter, and specifically, its scattering radiation patterns. We investigate such radiation patterns for diffraction and for scattering from a horizontal reflector considering a background isotropic model. The radiation patterns show considerable potential for trade-off between the parameters and the potentially limited resolution in their recovery. The radiation patterns of C11, C22, and C33 are well separated so that we expect to recover these parameters with limited trade-offs. However, the resolution of their recovery represented by recovered range of model wavenumbers varies between these parameters. We can only invert for the short wavelength components (reflection) of C33 while we can mainly invert for the long wavelength components (transmission) of the elastic coefficients C11 and C22 if we have large enough offsets. The elastic coefficients C13, C23, and C12 suffer from strong trade-offs with C55, C44, and C66, respectively. The trade-offs between C13 and C55, as well as C23 and C44, can be partially mitigated if we acquire P-SV and SV-SV waves. However, to reduce the trade-offs between C12 and C66, we require credible SH-SH waves. The analytical radiation patterns of the elastic constants are supported by numerical gradients of these parameters.
NASA Astrophysics Data System (ADS)
Petrov, P.; Newman, G. A.
2011-12-01
Recent developments in high resolution imaging technology of subsurface objects involves a combination of different geophysical measurements (gravity, EM and seismic). A joint image of the subsurface geophysical attributes (velocity, electrical conductivity and density) requires the consistent treatment of the different geophysical data due to their differing physical nature. For example, in conducting media, which is typical of the Earth's interior, EM energy propagation is defined by a diffusive mechanism and may be characterized by two specific length scales: wavelength and skin depth. However, the propagation of seismic signals is a multiwave process and is characterized by a set of wavelengths. Thus, to consistently treat seismic and electromagnetic data an additional length scale is needed for seismic data that does not directly depend on a wavelength and describes a diffusive process, similar to EM wave propagation in the subsurface. Works by Brown et al.(2005), Shin and Cha(2008), and Shin and Ha(2008) suggest that an artificial damping of seismic wave fields via Laplace-Fourier transformation can be an effective approach to obtain a seismic data that have similar spatial resolution to EM data. The key benefit of such transformation is that diffusive wave-field inversion works well for both data sets: seismic (Brown et al.,2005; Shin and Cha,2008) and electromagnetic (Commer and Newman,2008; Newman et al.,2010). With the recent interest in the Laplace-Fourier domain full waveform inversion, 3D fourth and second-order finite-difference schemes for modeling of seismic wave propagation have been developed (Petrov and Newman, 2010). Incorporation of attenuation and anisotropy into a velocity model is a necessary step for a more realistic description of subsurface media. Here we consider the extension of our method which includes attenuation and VTI anisotropy. Our approach is based on the integro-interpolation technique for velocity-stress formulation. Seven
NASA Astrophysics Data System (ADS)
Jesús Moral García, Francisco; Rebollo Castillo, Francisco Javier; Monteiro Santos, Fernando
2016-04-01
Maps of apparent electrical conductivity of the soil are commonly used in precision agriculture to indirectly characterize some important properties like salinity, water, and clay content. Traditionally, these studies are made through an empirical relationship between apparent electrical conductivity and properties measured in soil samples collected at a few locations in the experimental area and at a few selected depths. Recently, some authors have used not the apparent conductivity values but the soil bulk conductivity (in 2D or 3D) calculated from measured apparent electrical conductivity through the application of an inversion method. All the published works used data collected with electromagnetic (EM) instruments. We present a new software to invert the apparent electrical conductivity data collected with VERIS 3100 and 3150 (or the more recent version with three pairs of electrodes) using the 1D spatially constrained inversion method (1D SCI). The software allows the calculation of the distribution of the bulk electrical conductivity in the survey area till a depth of 1 m. The algorithm is applied to experimental data and correlations with clay and water content have been established using soil samples collected at some boreholes. Keywords: Digital soil mapping; inversion modelling; VERIS; soil apparent electrical conductivity.
NASA Astrophysics Data System (ADS)
Smirnov, M. Yu.; Korja, T.; Pedersen, L. B.
2009-04-01
Two electromagnetic arrays are used in the EMMA project to study conductivity structure of the Archaean lithosphere in the Fennoscandian Shield. The first array was operated during almost one year, while the second one was running only during the summer time. Twelve 5-components magnetotelluric instruments with fluxgate magnetometers recorded simultaneously time variations of Earth's natural electromagnetic field at the sites separated by c. 30 km. To better control the source field and to obtain galvanic distortion free responses we have applied horizontal spatial gradient (HSG) technique to the data. The study area is highly inhomogeneous, thus classical HSG might give erroneous results. The method was extended to include anomalous field effects by implementing multivariate analysis. The HSG transfer functions were then used to control static shift distortions of apparent resistivities. During the BEAR experiment 1997-2002, the conductance map of entire Fennoscandia was assembled and finally converted into 3D volume resistivity model. We have used the model, refined it to get denser grid around measurement area and calculated MT transfer functions after 3D modeling. We have used trial-and-error method in order to further improve the model. The data set was also inverted using 3D code of Siripunvaraporn (2005). In the first stage we have used homogeneous halfspace as starting model for the inversion. In the next step we have used final 3D forward model as apriori model. The usage of apriori information significantly stabilizes the inverse solution, especially in case of a limited amount of data available. The results show that in the Archaean Domain a conductive layer is found in the upper/middle crust on contrary to previous results from other regions of the Archaean crust in the Fennoscandian Shield. Data also suggest enhanced conductivity at the depth of c. 100 km. Conductivity below the depth of 200-250 km is lower than that of the laboratory based estimates
NASA Astrophysics Data System (ADS)
Wilkinson, Paul B.; Uhlemann, Sebastian; Chambers, Jonathan E.; Meldrum, Philip I.; Loke, Meng Heng
2015-03-01
Electrodes installed on active landslides and vulnerable earthworks to monitor changes in resistivity associated with moisture dynamics can be subject to movement. This affects the geoelectrical data and leads to errors in the resulting electrical resistivity tomography (ERT) images. This paper demonstrates the selection of appropriate ERT measurements to provide sensitivity to electrode displacements in both directions on a surface grid. Combinations of linear and equatorial dipole-dipole measurements are considered, which permit use on rectangular grids of any aspect ratio. A Gauss-Newton inversion scheme, initially based on simple homogeneous resistivity model calculations, is developed that allows for the incorporation of constraints based on the magnitude and direction of movement. The effects of the constraints are demonstrated with synthetic data, which are also used to show that displacement inversion can track electrodes positions during movement as a function of time. The conclusions of these simulations are subsequently confirmed by analogous experiments in a laboratory tank. The results show that tracking the positions of the electrodes is possible with sufficient accuracy, even in the presence of realistic subsurface resistivity structures, to correct the majority of distortions and resistivity anomalies caused by using the wrong electrode locations in ERT inversion. By incorporating estimates of the resistivity structure into the forward response modelling, the accuracy of the recovered displacements is improved. This also enables an iterative displacement and resistivity inversion to be developed that, for the first time, demonstrates the principle of using 3-D ERT data to monitor both subsurface geoelectrical properties and surface movements simultaneously.
NASA Astrophysics Data System (ADS)
Spichak, V. V.
2011-01-01
Possibilities for three-dimensional (3D) magnetotelluric (MT) sounding of local objects contained in the Earth's crust are estimated in a case study of the magma chamber of the Vesuvius volcano. Stochastic inversion of the model MT data by the Markov Chain Monte Carlo (MCMC) method has shown that the most efficient approach is not simultaneous but successive estimation of the geometry and the depth of the anomaly and the assessment of the conductivity distribution within the anomalous region. A zone of equivalence is revealed between the a priori estimate of the depth of the anomalous zone and the a posteriori distribution of electric conductivity within it. Based on the present estimation and previous results, an algorithm for determination of the parameters of local crustal anomaly is proposed.
The active portion of the Campi Flegrei caldera structure imaged by 3-D inversion of gravity data
NASA Astrophysics Data System (ADS)
Capuano, Paolo; Russo, Guido; Civetta, Lucia; Orsi, Giovanni; D'Antonio, Massimo; Moretti, Roberto
2013-10-01
We present an improved density model and a new structural map of the Neapolitan Yellow Tuff caldera, the active portion of the nested Campi Flegrei caldera. The model was built using a new 3-D inversion of the available high-precision gravity data, and a new digital terrain and marine model. The inversion procedure, based on a variable-depth lumped assembling of the subsurface gravity distribution via cell aggregation, gives better defined insights into the internal caldera architecture, that well agree with the available geological, geophysical, and geochemical data. The adopted 3-D gravity method is highly efficient for characterizing the shallow caldera structure (down to 3 km depth) and defining features related to regional or volcano tectonic lineaments and dynamics. In particular, the resulting density distribution highlights a pronounced density low in correspondence of the central portion of the caldera with a detail not available till now. The joint interpretation of the available data suggests a subsurface structural setting that supports a piecemeal collapse of the caldera, and allows the identification of its headwall. Positive gravity anomalies localize dense intrusions (presently covered by late volcanic deposits) along the caldera marginal faults, and the main structural lineaments both bordering the resurgent block and cutting the caldera floor. These results allow us to both refine the current geological-structural framework and propose a new structural map that highlights the caldera boundary and its internal setting. This map is useful to interpret the phenomena occurring during unrest, and to improve both short-term and long-term volcanic hazards assessment.
NASA Astrophysics Data System (ADS)
Tondi, R.; Cavazzoni, C.; Danecek, P.; Morelli, A.
2012-11-01
To obtain accurate and reliable estimations of the major lithological properties of the rock within a studied volume, geophysics uses the joint information provided by different geophysical datasets (e.g. gravimetric, magnetic, seismic). Representation of the different types of information entering the problem using probability density functions can provide the mathematical framework to formulate their combination. The maximum likelihood estimator of the resulting joint posterior probability density functions leads to the solution of the problem. However, one key problem appears to limit the use of this solver to an extensive range of real applications: information coming from potential fields that implies the presence of dense matrices in the resolving estimator. It is well known that dense matrix systems rapidly challenge both the algorithms and the computing platforms, and are not suited to high-resolution 3D geophysical analysis. In this study, we propose a procedure that allows us to obtain fast and reliable solutions of the joint posterior probability density functions in the presence of large gravity datasets and using sophisticated model parametrization. As it is particularly CPU-consuming, this 3D problem makes use of parallel computing to improve the performance and the accuracy of the simulations. Analysis of the correctness of the results, and the performance on different parallel environments, shows the portability and the efficiency of the code. This code is applied to a real experiment, where we succeed in recovering a 3D shear-wave velocity and density distribution within the upper mantle of the European continent, satisfying both the seismological and gravity data. On a multiprocessor machine, we have been able to handle forward and inverse calculations with a dense matrix of 215.66 Gb in 18 min, 20 s and 20 min, 54 s, respectively.
Koike, Narihiko; Ii, Satoshi; Yoshinaga, Tsukasa; Nozaki, Kazunori; Wada, Shigeo
2017-09-14
This paper presents a novel inverse estimation approach for the active contraction stresses of tongue muscles during speech. The proposed method is based on variational data assimilation using a mechanical tongue model and 3D tongue surface shapes for speech production. The mechanical tongue model considers nonlinear hyperelasticity, finite deformation, actual geometry from computed tomography (CT) images, and anisotropic active contraction by muscle fibers, the orientations of which are ideally determined using anatomical drawings. The tongue deformation is obtained by solving a stationary force-equilibrium equation using a finite element method. An inverse problem is established to find the combination of muscle contraction stresses that minimizes the Euclidean distance of the tongue surfaces between the mechanical analysis and CT results of speech production, where a signed-distance function represents the tongue surface. Our approach is validated through an ideal numerical example and extended to the real-world case of two Japanese vowels, /ʉ/ and /ɯ/. The results capture the target shape completely and provide an excellent estimation of the active contraction stresses in the ideal case, and exhibit similar tendencies as in previous observations and simulations for the actual vowel cases. The present approach can reveal the relative relationship among the muscle contraction stresses in similar utterances with different tongue shapes, and enables the investigation of the coordination of tongue muscles during speech using only the deformed tongue shape obtained from medical images. This will enhance our understanding of speech motor control. Copyright © 2017. Published by Elsevier Ltd.
Łeski, Szymon; Wójcik, Daniel K; Tereszczuk, Joanna; Swiejkowski, Daniel A; Kublik, Ewa; Wróbel, Andrzej
2007-01-01
Estimation of the continuous current-source density in bulk tissue from a finite set of electrode measurements is a daunting task. Here we present a methodology which allows such a reconstruction by generalizing the one-dimensional inverse CSD method. The idea is to assume a particular plausible form of CSD within a class described by a number of parameters which can be estimated from available data, for example a set of cubic splines in 3D spanned on a fixed grid of the same size as the set of measurements. To avoid specificity of particular choice of reconstruction grid we add random jitter to the points positions and show that it leads to a correct reconstruction. We propose different ways of improving the quality of reconstruction which take into account the sources located outside the recording region through appropriate boundary treatment. The efficiency of the traditional CSD and variants of inverse CSD methods is compared using several fidelity measures on different test data to investigate when one of the methods is superior to the others. The methods are illustrated with reconstructions of CSD from potentials evoked by stimulation of a bunch of whiskers recorded in a slab of the rat forebrain on a grid of 4x5x7 positions.
NASA Astrophysics Data System (ADS)
Windhari, Ayuty; Handayani, Gunawan
2015-04-01
The 3D inversion gravity anomaly to estimate topographical density using a matlab source code from gridded data provided by Parker Oldenburg algorithm based on fast Fourier transform was computed. We extend and improved the source code of 3DINVERT.M invented by Gomez Ortiz and Agarwal (2005) using the relationship between Fourier transform of the gravity anomaly and the sum of the Fourier transform from the topography density. We gave density contrast between the two media to apply the inversion. FFT routine was implemented to construct amplitude spectrum to the given mean depth. The results were presented as new graphics of inverted topography density, the gravity anomaly due to the inverted topography and the difference between the input gravity data and the computed ones. It terminates when the RMS error is lower than pre-assigned value used as convergence criterion or until maximum of iterations is reached. As an example, we used the matlab program on gravity data of Banten region, Indonesia.
Star-Lack, J; Nelson, S J; Kurhanewicz, J; Huang, L R; Vigneron, D B
1997-08-01
A T1 insensitive solvent suppression technique-band selective inversion with gradient dephasing (BASING)-was developed to suppress water and lipids for 1H magnetic resonance spectroscopy (MRS). BASING, which consists of a frequency selective RF inversion pulse surrounded by spoiler gradient pulses of opposite signs, was used to dephase stopband resonances and minimally impact passband metabolites. Passband phase linearity was achieved with a dual BASING scheme. Using the Shinnar-Le Roux algorithm, a highpass filter was designed to suppress water and rephase the lactate methyl doublet independently of TE, and water/lipid bandstop filters were designed for the brain and prostate. Phantom and in vivo experimental 3D PRESS CSI data were acquired at 1.5 T to compare BASING with CHESS and STIR suppression. With BASING, the measured suppression factor was over 100 times higher than with CHESS or STIR causing baseline distortions to be removed. It was shown that BASING can be incorporated into a variety of sequences to offer improved suppression in the presence of B1 and T1 inhomogeneites.
NASA Astrophysics Data System (ADS)
Afonso, J. C.; Fullea, J.; Yang, Y.; Griffin, W. L.; Jones, A. G.; Connolly, J.; Lebedev, S.; O'Reilly, S. Y.
2011-12-01
High-resolution imaging and characterization of the thermal and compositional structure of the lithospheric and sublithospheric upper mantle are the basis for understanding the formation and evolution of the lithosphere and the interaction between the crust-mantle and lithosphere-asthenosphere systems. Unfortunately, such imaging and characterization using available geophysical-geochemical methods still present unsolved and technically challenging problems. In this contribution we present a new full-3D multi-observable inversion method particularly designed for high-resolution (regional) thermal and compositional mapping of the lithosphere and sublithospheric upper mantle. Ambient noise tomography, multiple plane wave earthquake tomography, magnetotelluric, thermal, thermodynamic, and potential field modelling are all combined in a single thermodynamic-geophysical framework and appraised within a general probabilistic (Bayesian) formulation. This circumvents the problems of strong non-linearity involved in traditional inversions, provides highly refined seismic information, minimizes the problem of trade-off between temperature and composition in wave speeds, offers critical insights into incompatibilities between traditional stand-alone methods, and takes advantage of a priori local geochemical information. Both synthetic models and preliminary results in real-case examples will be used to discuss the benefits, robustness, and limitations of this method.
NASA Astrophysics Data System (ADS)
Choi, S.; Kim, C.; Kim, H. R.; Park, C.; Park, H. Y.
2015-12-01
We performed the marine magnetic and the bathymetry survey in the Lau basin for finding the submarine hydrothermal deposits in October 2009. We acquired magnetic and bathymetry datasets by using Overhouser Proton Magnetometer SeaSPY(Marine Magnetics Co.) and Multi-Beam Echo Sounder EM120(Kongsberg Co.). We conducted the data processing to obtain detailed seabed topography, magnetic anomaly and reduction to the pole(RTP). The Lau basin is one of the youngest back-arc basins in the Southwest Pacific. This region was a lot of hydrothermal activities and hydrothermal deposits. In particular, Tofua Arc(TA) in the Lau basin consists of various and complex stratovolcanos(from Massoth et al., 2007).), We calculated the magnetic susceptibility distribution of the TA19-1 seamount(longitude:176°23.5'W, latitude: 22°42.5'W)area using the RTP data by 3-D magnetic inversion from Jung's previous study(2013). Based on 2D 'compact gravity inversion' by Last & Kubik(1983), we expend it to the 3D algorithm using iterative reweighted least squares method with some weight matrices. The used weight matrices are two types: 1) the minimum gradient support(MGS) that controls the spatial distribution of the solution from Porniaguine and Zhdanov(1999); 2) the depth weight that are used according to the shape of subsurface structures. From the modeling, we derived the appropriate scale factor for the use of depth weight and setting magnetic susceptibility. Furthermore, we have to enter a very small error value to control the computation of the singular point of the inversion model that was able to be easily calculated for modeling. In addition, we applied separately weighted value for the correct shape and depth of the magnetic source. We selected the best results model by change to converge of RMS. Compared between the final modeled result and RTP values in this study, they are generally similar to the each other. But the input values and the modeled values have slightly little difference
NASA Astrophysics Data System (ADS)
Kiyan, D.; Jones, A. G.; Fullea, J.; Ledo, J.; Siniscalchi, A.; Romano, G.
2013-12-01
The overarching objectives of the second phase of the PICASSO (Program to Investigate Convective Alboran Sea System Overturn) project and the concomitant TopoMed (Plate re-organization in the western Mediterranean: Lithospheric causes and topographic consequences - an ESF EUROSCORES TOPO-EUROPE project) project are (i) to provide new electrical conductivity constraints on the crustal and lithospheric structures of the Atlas Mountains, and (ii) to test the hypotheses for explaining the observation of a 'missing' mantle root inferred from surface heat flow, gravity and geoid anomalies, elevation and seismic data modeling (i.e. Zeyen et al., 2005; Teixell et al., 2005; Fullea et al., 2010). We present the results from three-dimensional (3-D) MT inversion of data from two MT profiles employing the parallel version of Modular system for Electromagnetic inversion (ModEM; Egbert & Kelbert, 2012) code. For the profile in eastern Morocco, passing through Midelt, a distinct conductivity difference between the Middle-High Atlas (conductive) and Anti Atlas (resistive) correlates with the South Atlas Front fault, the depth extent of which appears to be limited to the uppermost mantle (approximately 55 km). In all inverse solutions, the crust and the upper mantle show a resistive signature (750 Ωm - 1,000 Ωm) beneath the Anti Atlas to a depth of 100 km, which is the part of stable West African Craton. Our results are at variance with the proposed thin lithosphere beneath the Middle-High Atlas as we see no evidence for a shallow asthenosphere. Our second profile lies in western Morocco traversing through Marrakech. For the first time, the electrical resistivity distribution in the crust and in the upper mantle of Western High Atlas has been studied. Our 3-D resistivity model shows that conductive (1-20 Ωm) western High Atlas is confined by two resistive basins (>1,000 Ωm), Souss basin to the south and Houz basin to the north. At the southern boundary of the western High Atlas
NASA Astrophysics Data System (ADS)
Bignardi, S.; Mantovani, A.; Abu Zeid, N.
2016-08-01
OpenHVSR is a computer program developed in the Matlab environment, designed for the simultaneous modeling and inversion of large Horizontal-to-Vertical Spectral Ratio (HVSR or H/V) datasets in order to construct 2D/3D subsurface models (topography included). The program is designed to provide a high level of interactive experience to the user and still to be of intuitive use. It implements several effective and established tools already present in the code ModelHVSR by Herak (2008), and many novel features such as: -confidence evaluation on lateral heterogeneity -evaluation of frequency dependent single parameter impact on the misfit function -relaxation of Vp/Vs bounds to allow for water table inclusion -a new cost function formulation which include a slope dependent term for fast matching of peaks, which greatly enhances convergence in case of low quality HVSR curves inversion -capability for the user of editing the subsurface model at any time during the inversion and capability to test the changes before acceptance. In what follows, we shall present many features of the program and we shall show its capabilities on both simulated and real data. We aim to supply a powerful tool to the scientific and professional community capable of handling large sets of HSVR curves, to retrieve the most from their microtremor data within a reduced amount of time and allowing the experienced scientist the necessary flexibility to integrate into the model their own geological knowledge of the sites under investigation. This is especially desirable now that microtremor testing has become routinely used. After testing the code over different datasets, both simulated and real, we finally decided to make it available in an open source format. The program is available by contacting the authors.
Ragnhild, L.; Ventris, P.; Osahon, G.
1995-08-01
OPL 210 lies in deepwater on the northwestern flank of the Niger Delta. The partners in this block are Allied Energy and The Statoil and BP Alliance. The license has a 5 year initial exploration phase and carries a 2 well commitment. At present the database comprises a 1 x 1 km grid of 2D seismic across the block, and 450 sq. km of 3D in an area of special interest. A larger 3D survey is planned for 1995. Little is known about the reservoir in the deep water, but we expect our main target to be ponded slope and basin turbidites. As such the bulk of the shelf well data available has little or no relevance to the play type likely to be encountered. Prior to drilling, seismic stratigraphy has been one of several methods used to generate a consistent predictive reservoir model. The excellent quality and high resolution of the 3D data have allowed identification and detailed description of several distinctive seismic facies. These facies are described in terms of their internal geometries and stacking patterns. The geometries are then interpreted based on a knowledge of depositional processes from analog slope settings. This enables a predictive model to be constructed for the distribution of reservoir within the observed facies. These predictions will be tested by one of the first wells drilled in the Nigerian deepwater in mid 1995.
Pavei, Gaspare; Seminati, Elena; Cazzola, Dario; Minetti, Alberto E
2017-01-01
The dynamics of body center of mass (BCoM) 3D trajectory during locomotion is crucial to the mechanical understanding of the different gaits. Forward Dynamics (FD) obtains BCoM motion from ground reaction forces while Inverse Dynamics (ID) estimates BCoM position and speed from motion capture of body segments. These two techniques are widely used by the literature on the estimation of BCoM. Despite the specific pros and cons of both methods, FD is less biased and considered as the golden standard, while ID estimates strongly depend on the segmental model adopted to schematically represent the moving body. In these experiments a single subject walked, ran, (uni- and bi-laterally) skipped, and race-walked at a wide range of speeds on a treadmill with force sensors underneath. In all conditions a simultaneous motion capture (8 cameras, 36 markers) took place. 3D BCoM trajectories computed according to five marker set models of ID have been compared to the one obtained by FD on the same (about 2,700) strides. Such a comparison aims to check the validity of the investigated models to capture the "true" dynamics of gaits in terms of distance between paths, mechanical external work and energy recovery. Results allow to conclude that: (1) among gaits, race walking is the most critical in being described by ID, (2) among the investigated segmental models, those capturing the motion of four limbs and trunk more closely reproduce the subtle temporal and spatial changes of BCoM trajectory within the strides of most gaits, (3) FD-ID discrepancy in external work is speed dependent within a gait in the most unsuccessful models, and (4) the internal work is not affected by the difference in BCoM estimates.
Modeling Coastal Salinity in Quasi 2D and 3D Using a DUALEM-421 and Inversion Software.
Davies, Gareth; Huang, Jingyi; Monteiro Santos, Fernando Acacio; Triantafilis, John
2015-01-01
Rising sea levels, owing to climate change, are a threat to fresh water coastal aquifers. This is because saline intrusions are caused by increases and intensification of medium-large scale influences including sea level rise, wave climate, tidal cycles, and shifts in beach morphology. Methods are therefore required to understand the dynamics of these interactions. While traditional borehole and galvanic contact resistivity (GCR) techniques have been successful they are time-consuming. Alternatively, frequency-domain electromagnetic (FEM) induction is potentially useful as physical contact with the ground is not required. A DUALEM-421 and EM4Soil inversion software package are used to develop a quasi two- (2D) and quasi three-dimensional (3D) electromagnetic conductivity images (EMCI) across Long Reef Beach located north of Sydney Harbour, New South Wales, Australia. The quasi 2D models discern: the dry sand (<10 mS/m) associated with the incipient dune; sand with fresh water (10 to 20 mS/m); mixing of fresh and saline water (20 to 500 mS/m), and; saline sand of varying moisture (more than 500 mS/m). The quasi 3D EMCIs generated for low and high tides suggest that daily tidal cycles do not have a significant effect on local groundwater salinity. Instead, the saline intrusion is most likely influenced by medium-large scale drivers including local wave climate and morphology along this wave-dominated beach. Further research is required to elucidate the influence of spring-neap tidal cycles, contrasting beach morphological states and sea level rise.
Pavei, Gaspare; Seminati, Elena; Cazzola, Dario; Minetti, Alberto E.
2017-01-01
The dynamics of body center of mass (BCoM) 3D trajectory during locomotion is crucial to the mechanical understanding of the different gaits. Forward Dynamics (FD) obtains BCoM motion from ground reaction forces while Inverse Dynamics (ID) estimates BCoM position and speed from motion capture of body segments. These two techniques are widely used by the literature on the estimation of BCoM. Despite the specific pros and cons of both methods, FD is less biased and considered as the golden standard, while ID estimates strongly depend on the segmental model adopted to schematically represent the moving body. In these experiments a single subject walked, ran, (uni- and bi-laterally) skipped, and race-walked at a wide range of speeds on a treadmill with force sensors underneath. In all conditions a simultaneous motion capture (8 cameras, 36 markers) took place. 3D BCoM trajectories computed according to five marker set models of ID have been compared to the one obtained by FD on the same (about 2,700) strides. Such a comparison aims to check the validity of the investigated models to capture the “true” dynamics of gaits in terms of distance between paths, mechanical external work and energy recovery. Results allow to conclude that: (1) among gaits, race walking is the most critical in being described by ID, (2) among the investigated segmental models, those capturing the motion of four limbs and trunk more closely reproduce the subtle temporal and spatial changes of BCoM trajectory within the strides of most gaits, (3) FD-ID discrepancy in external work is speed dependent within a gait in the most unsuccessful models, and (4) the internal work is not affected by the difference in BCoM estimates. PMID:28337148
NASA Astrophysics Data System (ADS)
Borisov, Dmitry; Singh, Satish C.; Fuji, Nobuaki
2015-09-01
Seismic full waveform inversion is an objective method to estimate elastic properties of the subsurface and is an important area of research, particularly in seismic exploration community. It is a data-fitting approach, where the difference between observed and synthetic data is minimized iteratively. Due to a very high computational cost, the practical implementation of waveform inversion has so far been restricted to a 2-D geometry with different levels of physics incorporated in it (e.g. elasticity/viscoelasticity) or to a 3-D geometry but using an acoustic approximation. However, the earth is three-dimensional, elastic and heterogeneous and therefore a full 3-D elastic inversion is required in order to obtain more accurate and valuable models of the subsurface. Despite the recent increase in computing power, the application of 3-D elastic full waveform inversion to real-scale problems remains quite challenging on the current computer architecture. Here, we present an efficient method to perform 3-D elastic full waveform inversion for time-lapse seismic data using a finite-difference injection method. In this method, the wavefield is computed in the whole model and is stored on a surface above a finite volume where the model is perturbed and localized inversion is performed. Comparison of the final results using the 3-D finite-difference injection method and conventional 3-D inversion performed within the whole volume shows that our new method provides significant reductions in computational time and memory requirements without any notable loss in accuracy. Our approach shows a big potential for efficient reservoir monitoring in real time-lapse experiments.
NASA Astrophysics Data System (ADS)
Gressent, A.; Muhle, J.; Rigby, M. L.; Lunt, M. F.; Ganesan, A.; Prinn, R. G.; Krummel, P. B.; Fraser, P. J.; Steele, P.; Weiss, R. F.; Harth, C. M.; O'Doherty, S.; Young, D.; Park, S.; Li, S.; Yao, B.; Reimann, S.; Vollmer, M. K.; Maione, M.; Arduini, I.; Lunder, C. R.
2016-12-01
Sulfuryl fluoride (SO2F2) is used increasingly as a fumigant to replace methyl bromide (CH3Br), which was regulated under the Montreal Protocol (1986). Mühle et al., J. Geophys. Res., 2009) showed that SO2F2 had been accumulating in the global atmosphere with a growth rate of 5±1% per year from 1978 to 2007. They also determined, using the 2D AGAGE box model, that SO2F2 has a total atmospheric lifetime of 36±11 years mainly driven by the oceanic uptake. In addition, the global warming potential of SO2F2 has been estimated to be ≈4780 for a 100-year time horizon (Papadimitriou et al., J. Phys. Chem., 2008), which is similar to the CFC-11 (CCl3F) GWP. Thus it is a potent greenhouse gas and its emissions are expected to continue to increase in the future. Here we report the first estimations of the SO2F2 emissions and its ocean sink from January 2006 to the end of 2015 on both the global scale using a 3D Eulerian chemical transport model (MOZART-4) solving a Main Chain Monte Carlo (MCMC) inversion, and on the regional scale using a 3D Lagrangian dispersion model (NAME) via the reversible-jump trans-dimensional MCMC approach (Lunt et al., Geosci. Model Dev., 2016). The mole fractions calculated on the global scale are used as boundary conditions for emission calculations over the NAME regions in North America, Europe, East Asia and Australia. For this 10-year inversion we use observations from the AGAGE (Advanced Global Atmospheric Gases Experiment) starting with six stations in 2006, which are La Jolla (California), Mace Head (Ireland), Cape Grim (Australia), Ragged Point (Barbados), Trinidad Head (California) and Cape Matatula (Samoa). We then add observations from Gosan (South Korea) in 2007, Jungfraujoch (Switzerland) in 2008, Shandiangzi (China) and Ny-Alesund (Norway) in 2010, and Monte Cimone (Italy) in 2011, reducing the uncertainty associated with the regions located close to these stations. Results are compared to (i) the total global SO2F2 emissions
NASA Astrophysics Data System (ADS)
Xiao, Mengchu
The Penobscot study area is located offshore Nova Scotia, Canada. There are two wells, which penetrate the highest potentially commercial bodies in the Abenaki Formation. In order to investigate the potential for locating additional hydrocarbon reservoirs, well log data was used and the Penobscot 3D seismic dataset was analyzed using Constrained Sparse Spike Inversion. From the well log data, low GR and SP values are an indication of a permeable sand layer, which provides the target zone in this study. Impedance - porosity crossplots gave the relationship between impedance and porosity, where a low impedance sand layer is correlated with high porosity. It was found that the target sand layer has low impedance, a feature recognizable from the inversion results. The porosity of the whole sand layer calculated by the linear function from the relationship between impedance and porosity. The calculation of thickness of this sand layer from maps representing different impedance intervals provided numeric evidence to show there is a low impedance sand layer in the well L-30. The pore thickness map results indicate there is greater pore thickness in well L-30 than B-41. It appears that the company drilled at the optimal location for the initial (L-30) well, and tested the extent of potential reservoir rock with the second (B-41) well. The potential reservoir is apparently fairly small, and restricted to the area around L-30. There may or may not be value in testing another location across a fault, but the rock behind the fault is likely not as high quality as at L-30 and the high-quality regions are small in size and not connected.
Wang, Yu; Aurelio, Daniele; Li, Wenyi; Tseng, Peter; Zheng, Zhaozhu; Li, Meng; Kaplan, David L; Liscidini, Marco; Omenetto, Fiorenzo G
2017-10-01
Structural proteins from naturally occurring materials are an inspiring template for material design and synthesis at multiple scales. The ability to control the assembly and conformation of such materials offers the opportunity to define fabrication approaches that recapitulate the dimensional hierarchy and structure-function relationships found in nature. A simple and versatile directed assembly method of silk fibroin, which allows the design of structures across multiple dimensional scales by generating and tuning structural color in large-scale, macro defect-free colloidally assembled 3D nanostructures in the form of silk inverse opals (SIOs) is reported. This approach effectively combines bottom-up and top-down techniques to obtain control on the nanoscale (through silk conformational changes), microscale (through patterning), and macroscale (through colloidal assembly), ultimately resulting in a controllable photonic lattice with predefined spectral behavior, with a resulting palette spanning almost the entire visible range. As a demonstration of the approach, examples of "multispectral" SIOs, paired with theoretical calculations and analysis of their response as a function of changes of lattice constants and refractive index contrast are illustrated. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
NASA Astrophysics Data System (ADS)
Vatankhah, Saeed; Renaut, Rosemary A.; Ardestani, Vahid E.
2017-09-01
Sparse inversion of gravity data based on L1-norm regularization is discussed. An iteratively reweighted least squares algorithm is used to solve the problem. At each iteration the solution of a linear system of equations and the determination of a suitable regularization parameter are considered. The LSQR iteration is used to project the system of equations onto a smaller subspace that inherits the ill-conditioning of the full space problem. We show that the gravity kernel is only mildly to moderately ill-conditioned. Thus, while the dominant spectrum of the projected problem accurately approximates the dominant spectrum of the full space problem, the entire spectrum of the projected problem inherits the ill-conditioning of the full problem. Consequently, determining the regularization parameter based on the entire spectrum of the projected problem necessarily over compensates for the non-dominant portion of the spectrum and leads to inaccurate approximations for the full-space solution. In contrast, finding the regularization parameter using a truncated singular space of the projected operator is efficient and effective. Simulations for synthetic examples with noise demonstrate the approach using the method of unbiased predictive risk estimation for the truncated projected spectrum. The method is used on gravity data from the Mobrun ore body, northeast of Noranda, Quebec, Canada. The 3-D reconstructed model is in agreement with known drill-hole information.
NASA Astrophysics Data System (ADS)
Kaban, Mikhail K.; Stolk, Ward; Tesauro, Magdala; El Khrepy, Sami; Al-Arifi, Nassir; Beekman, Fred; Cloetingh, Sierd A. P. L.
2016-11-01
We construct a new-generation 3D density model of the upper mantle of Asia and its surrounding areas based on a joint interpretation of several data sets. A recent model of the crust combining nearly all available seismic data is employed to calculate the impact of the crust on the gravity anomalies and observed topography and to estimate the residual mantle anomalies and residual topography. These fields are jointly inverted to calculate the density variations in the lithosphere and upper mantle down to 325 km. As an initial approximation, we estimate density variations using a seismic tomography model. Seismic velocity variations are converted into temperatures and then to density variations based on mineral physics constraints. In the Occam-type inversion, we fit both the residual mantle gravity anomalies and residual topography by finding deviations to the initial model. The obtained corrections improve the resolution of the initial model and reflect important features of the mantle structure that are not well resolved by the seismic tomography. The most significant negative corrections of the upper mantle density, found in the Siberian and East European cratons, can be associated with depleted mantle material. The most pronounced positive density anomalies are found beneath the Tarim and South Caspian basins, Barents Sea, and Bay of Bengal. We attribute these anomalies to eclogites in the uppermost mantle, which have substantially affected the evolution of the basins. Furthermore, the obtained results provide evidence for the presence of eclogites in the oceanic subducting mantle lithosphere.
NASA Astrophysics Data System (ADS)
Camacho, Antonio G.; Carmona, Enrique; García-Jerez, Antonio; Sánchez-Martos, Francisco; Prieto, Juan F.; Fernández, José; Luzón, Francisco
2015-11-01
This paper presents a gravimetric study (based on 382 gravimetric stations in an area about 32 km2) of a nearly flat basin: the Low Andarax valley. This alluvial basin, close to its river mouth, is located in the extreme south of the province of Almería and coincides with one of the existing depressions in the Betic Cordillera. The paper presents new methodological work to adapt a published inversion approach (GROWTH method) to the case of an alluvial valley (sedimentary stratification, with density increase downward). The adjusted 3D density model reveals several features in the topography of the discontinuity layers between the calcareous basement (2,700 kg/m3) and two sedimentary layers (2,400 and 2,250 kg/m3). We interpret several low density alignments as corresponding to SE faults striking about N140-145°E. Some detected basement elevations (such as the one, previously known by boreholes, in Viator village) are apparently connected with the fault pattern. The outcomes of this work are: (1) new gravimetric data, (2) new methodological options, and (3) the resulting structural conclusions.
SAR and scan-time optimized 3D whole-brain double inversion recovery imaging at 7T.
Pracht, Eberhard D; Feiweier, Thorsten; Ehses, Philipp; Brenner, Daniel; Roebroeck, Alard; Weber, Bernd; Stöcker, Tony
2017-09-14
The aim of this project was to implement an ultra-high field (UHF) optimized double inversion recovery (DIR) sequence for gray matter (GM) imaging, enabling whole brain coverage in short acquisition times ( ≈5 min, image resolution 1 mm(3) ). A 3D variable flip angle DIR turbo spin echo (TSE) sequence was optimized for UHF application. We implemented an improved, fast, and specific absorption rate (SAR) efficient TSE imaging module, utilizing improved reordering. The DIR preparation was tailored to UHF application. Additionally, fat artifacts were minimized by employing water excitation instead of fat saturation. GM images, covering the whole brain, were acquired in 7 min scan time at 1 mm isotropic resolution. SAR issues were overcome by using a dedicated flip angle calculation considering SAR and SNR efficiency. Furthermore, UHF related artifacts were minimized. The suggested sequence is suitable to generate GM images with whole-brain coverage at UHF. Due to the short total acquisition times and overall robustness, this approach can potentially enable DIR application in a routine setting and enhance lesion detection in neurological diseases. Magn Reson Med, 2017. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.
3D structural cartography based on magnetic and gravity data inversion - Case of South-West Algeria
NASA Astrophysics Data System (ADS)
Hichem, Boubekri; Mohamed, Hamoudi; Abderrahmane, Bendaoud; Ivan, Priezzhev; Karim, Allek
2015-12-01
This article presents the results of 3D aeromagnetic and gravity data inversion across the West African Craton (WAC) in South West Algeria. Although the used data have different origins and resolutions, the performed manual and automatic interpretation for each dataset shows a good correlation with some earlier geological studies of the region, major structural aspects of the locality, as well as other new structural features. Many curved faults parallel to the suture zone indicate the presence of terranes or the metacratonization of the WAC and a related fault network of great importance with NE-SW and NW-SE directions. The mega shear zones from north to south, which are visible at the surface in the Hoggar, are also observed along the Saharan Platform. The fact that these faults are observed since the Cambro-Ordovician in all crust (including the Saharan Basins) indicates that this area, which is situated on the border of the WAC, remained active during the entire period of time.
NASA Astrophysics Data System (ADS)
Petrov, P.; Newman, G. A.
2010-12-01
-Fourier domain we had developed 3D code for full-wave field simulation in the elastic media which take into account nonlinearity introduced by free-surface effects. Our approach is based on the velocity-stress formulation. In the contrast to conventional formulation we defined the material properties such as density and Lame constants not at nodal points but within cells. This second order finite differences method formulated in the cell-based grid, generate numerical solutions compatible with analytical ones within the range errors determinate by dispersion analysis. Our simulator will be embedded in an inversion scheme for joint seismic- electromagnetic imaging. It also offers possibilities for preconditioning the seismic wave propagation problems in the frequency domain. References. Shin, C. & Cha, Y. (2009), Waveform inversion in the Laplace-Fourier domain, Geophys. J. Int. 177(3), 1067- 1079. Shin, C. & Cha, Y. H. (2008), Waveform inversion in the Laplace domain, Geophys. J. Int. 173(3), 922-931. Commer, M. & Newman, G. (2008), New advances in three-dimensional controlled-source electromagnetic inversion, Geophys. J. Int. 172(2), 513-535. Newman, G. A., Commer, M. & Carazzone, J. J. (2010), Imaging CSEM data in the presence of electrical anisotropy, Geophysics, in press.
NASA Astrophysics Data System (ADS)
Kuvshinov, Alexey; Semenov, Alexey
2012-06-01
We present a novel frequency-domain inverse solution to recover the 3-D electrical conductivity distribution in the mantle. The solution is based on analysis of local C-responses. It exploits an iterative gradient-type method - limited-memory quasi-Newton method - for minimizing the penalty function consisting of data misfit and regularization terms. The integral equation code is used as a forward engine to calculate responses and data misfit gradients during inversion. An adjoint approach is implemented to compute misfit gradients efficiently. Further improvements in computational load come from parallelizing the scheme with respect to frequencies, and from setting the most time-consuming part of the forward calculations - calculation of Green's tensors - apart from the inversion loop. Convergence, performance, and accuracy of our 3-D inverse solution are demonstrated with a synthetic numerical example. A companion paper applies the strategy set forth here to real data.
NASA Astrophysics Data System (ADS)
Bentham, H. L. M.; Morgan, J. V.; Angus, D. A.
2016-12-01
The UK has a large volume of high level and intermediate level radioactive waste and government policy is to dispose of this waste in a Geological Disposal Facility (GDF). This will be a highly-engineered facility capable of isolating radioactive waste within multiple protective barriers, deep underground, to ensure that no harmful quantities of radioactivity ever reach the surface environment. Although no specific GDF site in the UK has been chosen, granite is one of the candidate host rocks due to its strength, in engineering terms, and because of its low permeability in consideration of groundwater movement. We design time-lapse seismic surveys to characterise geological models of naturally fractured granite with GDF-related tunnel damage zones at a potential disposal depth of 1000 m (the UK GDF might be shallower). Additionally, we use effective medium models to calculate the velocity change when the fracture density is increased in the damage zones, and find a reduction of 60 m/s in P-wave velocity when the fracture density is doubled. Next, we simulate seismic surveys and apply 3D Full Waveform Inversion (FWI) to see how well we can recover the low-velocity damage zones. Furthermore we evaluate the effectiveness of using a survey design consisting of surface and tunnel receivers (a combined array) to resolve the target. After applying FWI we find the velocity anomaly within the damage zone can be resolved to within 2 m/s (3%) and the shape of the damage zone is resolved to 12.5 m (within a single grid cell). Using the combined array we are able to resolve the anomaly strength and shape more completely. When we add further complexity to the model by including tunnel infrastructure, we conclude the combined array is essential in recovering the tunnel damage zone. Our findings show that it is beneficial to use 3D FWI and novel survey designs for characterising subtle variations as may be present in granite, information that could assist in the GDF site selection
Weng Cho Chew
2004-10-27
The project aim was the improvement, evaluation, and application of one dimensional (1D) inversion and development and application of three dimensional (3D) inversion to processing of data collected at waste pits at the Idaho National Engineering and Environmental Laboratory. The inversion methods were intended mainly for the Very Early Time Electromagnetic (VETEM) system which was designed to improve the state-of-the-art of electromagnetic imaging of the shallow (0 to about 5m) subsurface through electrically conductive soils.
NASA Astrophysics Data System (ADS)
Meqbel, N. M.; Egbert, G. D.; Kelbert, A.
2011-12-01
Long period (10-20,000 s) magnetotelluric (MT) data are being acquired in a series of temporary arrays deployed across the continental United States through the EMScope component of EarthScope. MT deployments in 2006-2011 have acquired data at 325 sites on an approximately regular grid, with the same nominal spacing as the USArray broadband seismic transportable array (~70 km). The MT sites span a rectangular area from NW Washington to NW Colorado. Here we present results of a 3-D inversion of the full data set. A number of conductive and resistive features appear consistently in the crust and upper mantle in essentially all of a large suite of 3-D inverse solutions. Extensive areas of high conductivity are found in the lower crust (up to a depth of ~ 40 km) beneath the Basin & Range in southeastern Oregon, as imaged by Patro and Egbert (2008). In our new model, this feature extends further to the south and to the east, where it merges with somewhat deeper (uppermost mantle) conductivities beneath the Yellowstone-Snake River Plain. This deeper feature, which extends from Yellowstone to the SW into northeastern Nevada, coincides with the track of the Yellowstone hotspot discussed e.g., in Smith et. al. (2008). The lower crust and the uppermost mantle in the northeastern part of the domain, covering the area from eastern Washington to Montana and continuing south to Wyoming, is generally resistive, with a few localized exceptions. This resistive zone coincides with high velocities discussed and interpreted, e.g., by Yang et. al. (2008) as thick, stable Proterozoic lithosphere. A number of large-scale anomalous features also appear consistently in the upper mantle, at depths of ~ 50 km to 300 km. Most striking is a zone of high resistivity on the western edge of the domain, beneath western Oregon, Washington and northern California in the area occupied by oceanic lithosphere of the Juan de Fuca Plate, which has subducted beneath the relatively more conductive
NASA Astrophysics Data System (ADS)
Booker, J. R.; Mackie, R. L.; Burd, A. I.
2016-12-01
We have previously presented evidence that MT arrays can image 3D structure outside their footprint (Paper GP23C-07, Fall AGU 2016). We showed that non-overlapping arrays in Argentina apparently imaged the same vertical conductor arising from the mantle deeper than 250 km. Because of the geodynamical importance of such a structure in the back-arc of the Andes it is important ascertain whether it is real. We compared inversions in which the competition between vertical and horizontal smoothing was changed by the presence or absence of a tear in the model smoothness constraint at the top of the Mantle Transition Zone (MTZ) at 410 km depth and found that the vertical structure was not present when the model had a tear. We suggested that when there is a tear, horizontal smoothing of resistive mantle under the array wins the competition under the oceans. This reduces the conductivity of the sub-oceanic mantle above 410 km. With no tear, the sub-oceanic mantle is more conductive due to vertical smoothing of a basal half space. The Pacific and Atlantic oceans have significant responses on the land which depend on the sub-oceanic mantle. Thus the presence or absence of the tear influences the effect of the ocean on the land responses and consequently the land structure. To test this hypothesis in detail, we have implemented alternative ways to change how the regularization and boundary conditions control the sub-oceanic mantle that do not involve a tear. We report the results.
NASA Astrophysics Data System (ADS)
Takahashi, Toru; Coulier, Pieter; Darve, Eric
2017-07-01
We investigate an efficient preconditioning of iterative methods (such as GMRES) for solving dense linear systems Ax = b that follow from a boundary element method (BEM) for the 3D Helmholtz equation, focusing on the low-frequency regime. While matrix-vector products in GMRES can be accelerated through the low-frequency fast multipole method (LFFMM), the BEM often remains computationally expensive due to the large number of GMRES iterations. We propose the application of the inverse fast multipole method (IFMM) as a preconditioner to accelerate the convergence of GMRES. The IFMM is in essence an approximate direct solver that uses a multilevel hierarchical decomposition and low-rank approximations. The proposed IFMM-based preconditioning has a tunable parameter ε that balances the cost to construct a preconditioner M, which is an approximation of A-1, and the cost to perform the iterative process by means of M. Namely, using a small (respectively, large) value of ε takes a long (respectively, short) time to construct M, while the number of iterations can be small (respectively, large). A comprehensive set of numerical examples involving various boundary value problems with complicated geometries and mixed boundary conditions is presented to validate the efficiency of the proposed method. We show that the IFMM preconditioner (with a nearly optimal ε of 10-2) clearly outperforms some common preconditioners for the BEM, achieving 1.2-10.8 times speed-up of the computations, in particular when the scale of the underlying scatterer is about five wavelengths or more. In addition, the IFMM preconditioner is capable of solving complicated problems (in a reasonable amount of time) that BD preconditioner can not.
Commer, Michael; Helwig, Stefan, L.; Hordt, Andreas; Scholl,Carsten; Tezkan, Bulent
2006-06-14
Three long-offset transient electromagnetic (LOTEM) surveyswerecarried out at the active volcano Merapi in Central Java (Indonesia)during the years 1998, 2000, and 2001. The measurements focused on thegeneral resistivity structure of the volcanic edifice at depths of 0.5-2km and the further investigation of a southside anomaly. The measurementswere insufficient for a full 3D inversion scheme, which could enable theimaging of finely discretized resistivity distributions. Therefore, astable, damped least-squares joint-inversion approach is used to optimize3D models with a limited number of parameters. The mode ls feature therealistic simulation of topography, a layered background structure, andadditional coarse 3D blocks representing conductivity anomalies.Twenty-eight LOTEM transients, comprising both horizontal and verticalcomponents of the magnetic induction time derivative, were analyzed. Inview of the few unknowns, we were able to achieve reasonable data fits.The inversion results indicate an upwelling conductor below the summit,suggesting hydrothermal activity in the central volcanic complex. Ashallow conductor due to a magma-filled chamber, at depths down to 1 kmbelow the summit, suggested by earlier seismic studies, is not indicatedby the inversion results. In conjunction with an anomalous-density model,derived from arecent gravity study, our inversion results provideinformation about the southern geological structure resulting from amajor sector collapse during the Middle Merapi period. The density modelallows to assess a porosity range andthus an estimated vertical salinityprofile to explain the high conductivities on a larger scale, extendingbeyond the foothills of Merapi.
NASA Astrophysics Data System (ADS)
Barnoud, A.; Coutant, O.; Bouligand, C.
2013-12-01
We propose to use a Bayesian methodology combined with a grid node discretization to invert linearly for 3D density distributions. The inversion and the forward modeling are derived from seismological travel-time inversion techniques in order to facilitate joint inversion or interpretation of density and seismic velocity models. The Bayesian method (Tarantola, 2005) introduces covariance matrices to regularize this ill-posed problem and reduce the non-uniqueness of the solution. Spatial covariances and grid discretization favor smooth and compact solutions that compare to usual seismic tomographic results. Compared to similar approaches our development includes i) the computation of the gravity field for linear vertical gradients and layers, including surface topography, a standard model description in seismology, ii) an explicit formulation of the a-priori covariance matrix. This last point allows to easily modify the spatial a-priori covariance (or scale, or wavelength) and hence, to perform successive linear inversions at different wavelengths. A series of synthetic tests is performed for validation, and used to show the advantage and limitation of this methodology. The method is appropriate for crustal and volcanological area studies, and allows a natural coupling with seismological inversions (Coutant et al., 2012). We present here two case studies for 3D gravity inversions. First, the inversion is performed in a crustal alpine context, the area of the well studied Ivrea Body in Italy. Secondly, we apply the inversion to gravity data from the volcanic island of Basse-Terre whose internal structure is badly constrained. We use data from previous studies supplemented with new high quality data acquired in 2012 within the frame of the Domoscan project. A 3D density model of the island of Basse-Terre is derived for the first time.
NASA Astrophysics Data System (ADS)
Meqbel, Naser M.; Egbert, Gary D.; Wannamaker, Philip E.; Kelbert, Anna; Schultz, Adam
2014-09-01
Long period (10-20,000 s) magnetotelluric (MT) data are being acquired across the continental USA on a quasi-regular grid of ˜70 km spacing as an electromagnetic component of the National Science Foundation EarthScope/USArray Program. These data are sensitive to fluids, melts, and other orogenic indicators, and thus provide a valuable complement to other components of EarthScope. We present and interpret results of 3-D MT data inversion from 325 sites acquired from 2006-2011 to provide a regional scale view of electrical resistivity from the middle crust to nearly the mantle transition zone, covering an area from NW Washington to NW Colorado. Beneath the active extensional subprovinces in the south-central region, on average we see a resistive upper crust, and then extensive areas of low resistivity in the lower crust and uppermost mantle. Further below, much of the upper half of the upper mantle appears moderately resistive, then subsequently the lower upper mantle becomes moderately conductive. This column suggests a dynamic process of moderately hydrated and fertile deeper upper mantle upwelling during extension, intersection of that material with the damp solidus causing dehydration and melting, and upward exodus of generated mafic melts to pond and exsolve saline fluids near Moho levels. Lithosphere here is very thin. To the east and northeast, thick sections of resistive lithosphere are imaged under the Wyoming and Medicine Hat Cratons. These are punctuated with numerous electrically conductive sutures presumably containing graphitic or sulfide-bearing meta-sediments deeply underthrust and emplaced during ancient collisions. Below Cascadia, the subducting Juan de Fuca and Gorda lithosphere appears highly resistive. Suspected oceanic lithosphere relicts in the central NW part of the model domain also are resistive, including the accreted “Siletzia” terrane beneath the Coast Ranges and Columbia Embayment, and the seismically fast “slab curtain” beneath
NASA Astrophysics Data System (ADS)
Miller, Craig A.; Williams-Jones, Glyn; Fournier, Dominique; Witter, Jeff
2017-02-01
Active, large volume, silicic magma systems are potentially the most hazardous form of volcanism on Earth. Knowledge of the location, size, and physical properties of silicic magma reservoirs, is therefore important for providing context in which to accurately interpret monitoring data and make informed hazard assessments. Accordingly, we present the first geophysical image of the Laguna del Maule volcanic field magmatic system, using a novel 3D inversion of gravity data constrained by thermodynamic modelling. The joint analysis of gravity and thermodynamic data allows for a rich interpretation of the magma system, and highlights the importance of considering the full thermodynamic effects on melt density, when interpreting gravity models of active magmatic systems. We image a 30 km3, low density, volatile rich magma reservoir, at around 2 km depth, containing at least 85% melt, hosted within a broader 115 km3 body interpreted as wholly or partially crystallised (>70% crystal) cumulate mush. Our model suggests a magmatic system with shallow, crystal poor magma, overlying deeper, crystal rich magma. Even though a large density contrast (-600 kg/m3) with the surrounding crust exists, the lithostatic load is 50% greater than the magma buoyancy force, suggesting buoyancy alone is insufficient to trigger an eruption. The reservoir is adjacent to the inferred extension of the Troncoso fault and overlies the location of an intruding sill, driving present day deformation. The reservoir is in close proximity to the 2.0 km3 Nieblas (rln) eruption at 2-3 ka, which we calculate tapped approximately 7% of the magma reservoir. However, we suggest that the present day magma system is not large enough to have fed all post-glacial eruptions, and that the location, or size of the system may have migrated or varied over time, with each eruption tapping only a small aliquot of the available magma. The presence of a shallow reservoir of volatile rich, near liquidus magma, in close
NASA Astrophysics Data System (ADS)
Meqbel, N. M.; Egbert, G. D.; Wannamaker, P. E.; Kelbert, A.; Schultz, A.
2013-12-01
Long period (10-20,000 s) magnetotelluric (MT) data are being acquired across the continental USA on a quasi-regular grid of ~70 km spacing as an electromagnetic component of the National Science Foundation EarthScope/USArray Program. These data are sensitive to fluids, melts, and other orogenic indicators, and thus provide a valuable complement to other components of EarthScope. We present and interpret results of 3-D MT data inversion from 325 sites acquired from 2006-2011 to provide a regional scale view of electrical resistivity from the middle crust to nearly the mantle transition zone, covering an area from NW Washington to NW Colorado. Extensive areas of low resistivity are imaged in the lower crust and uppermost mantle beneath the extensional provinces, most plausibly explained by underplated, hybridized magmas and associated exsolved highly saline fluids. These pervasive low resistivities show aligned or 'streaky' textures roughly parallel to seismic fast-axes, possibly reflecting widespread flow induced alignment of melt in this area. Thick sections of resistive lithosphere imaged in the eastern and northeastern part of the domain coincide spatially with the Wyoming and Medicine Hat Cratons. Sutures bounding these cratonic blocks are electrically conductive most likely due to meta-sediments emplaced during ancient collisions. Below the Cascadia forearc, the subducting Juan de Fuca and Gorda lithosphere appears highly resistive. Other resistive zones in the NW part of the domain may denote relict oceanic lithosphere: the accreted 'Siletzia' terrane beneath the Coast Ranges and Columbia Embayment, and the seismically fast 'slab curtain' beneath eastern Idaho interpreted by others as stranded Farallon lithosphere. Quasi-horizontal patches of low resistivity in the deep crust beneath the Cascade volcanic arc and fore-arc likely represent fluids evolved from breakdown of hydrous minerals in the down-going slab. In the backarc, low resistivities concentrate in
NASA Astrophysics Data System (ADS)
Morgan, Joanna; Warner, Michael; Arnoux, Gillean; Hooft, Emilie; Toomey, Douglas; VanderBeek, Brandon; Wilcock, William
2016-02-01
3-D full-waveform inversion (FWI) is an advanced seismic imaging technique that has been widely adopted by the oil and gas industry to obtain high-fidelity models of P-wave velocity that lead to improvements in migrated images of the reservoir. Most industrial applications of 3-D FWI model the acoustic wavefield, often account for the kinematic effect of anisotropy, and focus on matching the low-frequency component of the early arriving refractions that are most sensitive to P-wave velocity structure. Here, we have adopted the same approach in an application of 3-D acoustic, anisotropic FWI to an ocean-bottom-seismometer (OBS) field data set acquired across the Endeavour oceanic spreading centre in the northeastern Pacific. Starting models for P-wave velocity and anisotropy were obtained from traveltime tomography; during FWI, velocity is updated whereas anisotropy is kept fixed. We demonstrate that, for the Endeavour field data set, 3-D FWI is able to recover fine-scale velocity structure with a resolution that is 2-4 times better than conventional traveltime tomography. Quality assurance procedures have been employed to monitor each step of the workflow; these are time consuming but critical to the development of a successful inversion strategy. Finally, a suite of checkerboard tests has been performed which shows that the full potential resolution of FWI can be obtained if we acquire a 3-D survey with a slightly denser shot and receiver spacing than is usual for an academic experiment. We anticipate that this exciting development will encourage future seismic investigations of earth science targets that would benefit from the superior resolution offered by 3-D FWI.
NASA Astrophysics Data System (ADS)
Gao, J.; Zhang, H.
2015-12-01
Near surface geophysical exploration for the purpose of engineering design or construction For this reason, geophysical imaging demands a higher resolution and a better quantitative interpretation. Seismic travel time tomography and direct current resistivity tomography are two main methods for the near surface survey. Because of the limited coverage of observation system and the complex physical relationship between physical parameters and observations, individual geophysical method suffers issues of non-uniqueness and resolution limitation to some degree. We have developed a joint inversion method to combine seismic travel time tomography and full channel resistivity tomography. For the full channel resistivity survey, it uses two electrodes for power supply and all the other electrodes for recording. Compared with the traditional resistivity method, it collects more data and has a better model converge. Our joint inversion strategy relies on the structure constraint enforced through minimizing cross gradients between seismic velocity and resistivity models (Gallardo, 2003). For resistivity tomography, sensitivity kernels are obtained through the adjoint method by solving the electrostatic field equation with the finite-difference method. For seismic travel time tomography, ray paths and travel times are calculated using the fast marching method. We have tested our joint inversion method for a 2D cross-hole problem where two small zones with high and low velocity/resistivity anomalies. Seismic/electrical sources/receivers are installed in two boreholes. For separate seismic inversion, the smearing effect is evident and two anomaly zones are distorted and misplaced. For separate electric resistivity inversion, although two anomaly zones are positioned correctly their values are not accurate. By joint inversion, two velocity anomaly zones are clearly imaged and the smearing effect is greatly reduced. In comparison, for the resistivity model, the two anomaly zones
NASA Astrophysics Data System (ADS)
Rodríguez Cardozo, Félix; Hjörleifsdóttir, Vala; Caló, Marco
2017-04-01
Moment tensor inversions for intermediate and small earthquakes (M. < 4.5) are challenging as they principally excite relatively short period seismic waves that interact strongly with local heterogeneities. Incorporating detailed regional 3D velocity models permits obtaining realistic synthetic seismograms and recover the seismic source parameters these smaller events. Two 3D regional velocity models have recently been developed for Mexico, using surface waves and seismic noise tomography (Spica et al., 2016; Gaite et al., 2015), which could be used to model the waveforms of intermediate magnitud earthquakes in this region. Such models are parameterized as layered velocity profiles and for some of the profiles, the velocity difference between two layers are considerable. The "jump" in velocities between two layers is inconvenient for some methods and algorithms that calculate synthetic waveforms, in particular for the method that we are using, the spectral element method (SPECFEM3D GLOBE, Komatitsch y Tromp, 2000), when the mesh does not follow the layer boundaries. In order to make the velocity models more easily implementec in SPECFEM3D GLOBE it is neccesary to apply a homogenization algorithm (Capdeville et al., 2015) such that the (now anisotropic) layer velocities are smoothly varying with depth. In this work, we apply a homogenization algorithm to the regional velocity models in México for implementing them in SPECFEM3D GLOBE, calculate synthetic waveforms for intermediate-magnitude earthquakes in México and invert them for the seismic moment tensor.
Design optimization of axial flow hydraulic turbine runner: Part I - an improved Q3D inverse method
NASA Astrophysics Data System (ADS)
Peng, Guoyi; Cao, Shuliang; Ishizuka, Masaru; Hayama, Shinji
2002-06-01
With the aim of constructing a comprehensive design optimization procedure of axial flow hydraulic turbine, an improved quasi-three-dimensional inverse method has been proposed from the viewpoint of system and a set of rotational flow governing equations as well as a blade geometry design equation has been derived. The computation domain is firstly taken from the inlet of guide vane to the far outlet of runner blade in the inverse method and flows in different regions are solved simultaneously. So the influence of wicket gate parameters on the runner blade design can be considered and the difficulty to define the flow condition at the runner blade inlet is surmounted. As a pre-computation of initial blade design on S2m surface is newly adopted, the iteration of S1 and S2m surfaces has been reduced greatly and the convergence of inverse computation has been improved. The present model has been applied to the inverse computation of a Kaplan turbine runner. Experimental results and the direct flow analysis have proved the validation of inverse computation. Numerical investigations show that a proper enlargement of guide vane distribution diameter is advantageous to improve the performance of axial hydraulic turbine runner. Copyright
NASA Astrophysics Data System (ADS)
Chen, P.; Lee, E.; Jordan, T. H.; Maechling, P. J.
2011-12-01
Accurate and rapid CMT inversion is important for seismic hazard analysis. We have developed an algorithm for very rapid full-wave CMT inversions in a 3D Earth structure model and applied it on earthquakes recorded by the Southern California Seismic Network (SCSN). The procedure relies on the use of receiver-side Green tensors (RGTs), which comprise the spatial-temporal displacements produced by the three orthogonal unit impulsive point forces acting at the receiver. We have constructed a RGT database for 219 broadband stations in Southern California using an updated version of the 3D SCEC Community Velocity Model (CVM) version 4.0 and a staggered-grid finite-difference code. Finite-difference synthetic seismograms for any earthquake in our modeling volume can be simply calculated by extracting a small, source-centered volume from the RGT database and applying the reciprocity principle. We have developed an automated algorithm that combines a grid-search for suitable epicenter and focal mechanisms with a gradient-descent method that further refines the grid-search results. In this algorithm, the CMT solutions are inverted near real-time by using waveform in a 3D Earth structure. Comparing with the CMT solutions provided by the Southern California Seismic Network (SCSN) shows that our solutions generally provide better fit to the observed waveforms. Our algorithm may provide more robust CMT solutions for earthquakes in Southern California. In addition, the rapid and accurate full-wave CMT inversion has potential to extent to accurate near real-time ground-motion prediction based on 3D structure model for earthquake early warning purpose. When combined with real-time telemetered waveform recordings, our algorithm can provide (near) real-time ground-motion forecast.
NASA Astrophysics Data System (ADS)
Folsom, M.; Pepin, J.; Person, M. A.; Kelley, S.; Peacock, J.
2016-12-01
Twelve magnetotelluric (MT) soundings were collected along a 40 km profile crossing the Rio Grande rift and a portion of the Socorro Magma Body (SMB). A comparison of 1D, 2D and 3D inverse models highlight the strengths and weaknesses of the respective methods. 2D inversion results are distorted by the 3D nature of the data at longer periods, producing conductive artifacts at depths greater than 3 km. We demonstrate through a 3D forward modelling exercise how it is possible to recreate this effect by placing large resistive and conductive features off of an otherwise perfectly 2D resistivity model. Investigators that image deep conductors using 2D inversion codes should consider the influence of off-axis 3D features. Interpretation of the models currently show no indication of the SMB, but outlines the geometry of syn-rift and pre-rift sediments at the "Socorro Constriction", the southern terminus of the Albuquerque Basin. A strong, northward trending conductor 2-3 km deep and less than 2 ohm-m is coincident with the rift, creating a reversal of induction arrow direction at this point. This is interpreted as deep basin brines, perhaps influenced by evaporates hosted in the Permian Abo and Yeso formations. It has been noted that Rio Grande salinity increases in a stepwise manner, coincident with the terminal ends of sedimentary basins. Our geophysical models suggest a possible connection between rift-bounding faults and deep sedimentary brines, which likely impact the water quality of the Rio Grande. Future work includes adding additional MT stations to better constrain off-axis features and their relationship to the Rio Grande.
NASA Astrophysics Data System (ADS)
Löwer, Alexander; Junge, Andreas
2017-05-01
The influence of anisotropic conductivity structures on magnetotelluric transfer functions is not easy to analyse in its entire complexity. In this study, we investigate the spatial and frequency-dependent behaviour of phase tensors and tipper vectors above a 3D anisotropic conductivity anomaly. The anomaly consists of a simple cubic block embedded in a homogeneous half space. Using a 3D FD code, we compare an isotropic, 2 anisotropic models with an anisotropy factor of 10 and one anisotropic model with the anisotropy factor of 100. The results show characteristic differences between the isotropic and anisotropic cases. For the anisotropic anomalies, the tipper vectors are parallel over the entire area despite the 3D geometry of the anomalous body. The size of the tipper vectors depends on the position of the site relative to the anomaly's boundaries and the direction of the anisotropic strike. Above the anomalous anisotropic body, the main diagonal elements of the phase tensor show the well-known split. Outside the anomaly, the phase tensor principal axis rotates according to the site position in contrast to the constant tipper direction. The 3D inversion of the forward data using an isotropic 3D code (ModEM) yields a very good fit for all cases. Whereas the inversion result matches the isotropic model, wave-like structures with high conductivity contrast occur for the anisotropic models. These structures extend far beyond the extension of the original anomalous body. Thus, the study reveals important indications of the existence of anisotropic conductivity structures for observed magnetotelluric transfer functions.
NASA Astrophysics Data System (ADS)
Geng, Meixia; Welford, J. Kim; Farquharson, Colin
2017-04-01
While seismic methods provide the best geophysical methods for characterizing crustal structure, regional potential field studies and, specifically, constrained 3-D potential field inversion studies, provide an efficient means of bridging between seismic lines and obtaining regional views of deep structure. Most existing potential field inversion codes have been developed for the mining industry with the goal of delineating dense bodies within less dense half-spaces. While these codes can be successfully applied to crustal-scale targets, they are not designed to generate models with the kind of depth-dependent layering expected within the crust and upper mantle and consequently, the results must be interpreted with such limitations in mind. The development of improved inversion codes that will produce results that better conform to known density distributions within the crust and uppermost mantle will revolutionize the application of potential field methods for the study of rifted continental margins where only limited seismic constraints are available. Through insights gained from using existing inversion codes, we have developed a 3D inversion algorithm based on the constrained stochastic method and adapted it for use in regional crustal-scale studies. The new method honours existing sparse seismic constraints and generates models that can reproduce sharp boundaries at the base of the crust as well as more gradational density variations with depth for the crust to upper mantle transition. The improved regional crustal models provide crustal thickness estimates and crustal stretching factors that agree with the sparsely available seismic constraints, while also generating more realistic Earth models. Both synthetic and real examples from offshore eastern Canada, will be used to demonstrate the power of the new method.
NASA Astrophysics Data System (ADS)
McNulty, David; Geaney, Hugh; Carroll, Elaine; Garvey, Shane; Lonergan, Alex; O'Dwyer, Colm
2017-02-01
Engineering Co3O4 nanoparticles into highly ordered, 3D inverse opal (IO) structures is shown to significantly improve their performance as more efficient conversion mode Li-ion anode materials. By comparison with Co3O4 microparticles, the advantages of the porous anode architecture are clearly shown. The inverse opal material markedly enhances specific capacity and capacity retention. The impact of various C rates on the rate of the initial charge demonstrates that higher rate charging (10 C) was much less destructive to the inverse opal structure than charging at a slow rate (0.1 C). Slower C rates that affect the IO structure resulted in higher specific capacities (more Li2O) as well as improved capacity retention. The IO structures cycle as CoO, which improves Coulombic efficiency and limits volumetric changes, allowing rate changes more efficiently. This work demonstrates how 3D IOs improve conversion mode anode material performance in the absence of additive or binders, thus enhancing mass transport of Li2O charge-discharge product through the open structure. This effect mitigates clogging by structural changes at slow rates (high capacity) and is beneficial to the overall electrochemical performance.
NASA Astrophysics Data System (ADS)
Vatankhah, Saeed; Ardestani, Vahid E.; Renaut, Rosemary A.
2015-01-01
The χ2 principle and the unbiased predictive risk estimator are used to determine optimal regularization parameters in the context of 3-D focusing gravity inversion with the minimum support stabilizer. At each iteration of the focusing inversion the minimum support stabilizer is determined and then the fidelity term is updated using the standard form transformation. Solution of the resulting Tikhonov functional is found efficiently using the singular value decomposition of the transformed model matrix, which also provides for efficient determination of the updated regularization parameter each step. Experimental 3-D simulations using synthetic data of a dipping dike and a cube anomaly demonstrate that both parameter estimation techniques outperform the Morozov discrepancy principle for determining the regularization parameter. Smaller relative errors of the reconstructed models are obtained with fewer iterations. Data acquired over the Gotvand dam site in the south-west of Iran are used to validate use of the methods for inversion of practical data and provide good estimates of anomalous structures within the subsurface.
NASA Astrophysics Data System (ADS)
Bologna, Mauricio S.; Egbert, Gary D.; Padilha, Antonio L.; Pádua, Marcelo B.; Vitorello, Ícaro
2017-09-01
We present a magnetotelluric (MT) study in the northeastern part of the São Francisco Craton that encompasses an Archean-Proterozoic terrain, the Serrinha Block, breached by a rift basin developed mostly in Early Cretaceous times during the opening of the South Atlantic Ocean. Even though the MT sites are regularly spaced, the profiles have different orientations from one another, making the data distribution over the area highly uneven and therefore non-ideal for 3-D modeling. However, the data set is very complex, with dimensionality analysis indicating prevalence of 3-D geoelectric structure. Results from 3-D inversion are evaluated for robustness and potentiality for yielding tectonic information. At upper crustal depths, the resulting 3-D model is coherent with surface geology, whereas at mid and lower crustal depths more cryptic structures are revealed, likely of Palaeoproterozoic age. The most striking features in the model are several strong (∼1 Ωṡm) crustal conductors beneath the central part of the Serrinha Block, which we attribute to a Palaeoproterozoic oceanic plate subduction and arc-continent collision event involving the Rio Itapicuru Greenstone Belt and the basement of the Serrinha Block. The west-dipping geometry of these conductors provides a constraint on subduction polarity and gives support to tectonic evolutionary models proposing that the Rio Itapicuru Belt was formed in an island arc environment.
NASA Astrophysics Data System (ADS)
Malovichko, M.; Khokhlov, N.; Yavich, N.; Zhdanov, M.
2017-10-01
Over the recent decades, a number of fast approximate solutions of Lippmann-Schwinger equation, which are more accurate than classic Born and Rytov approximations, were proposed in the field of electromagnetic modeling. Those developments could be naturally extended to acoustic and elastic fields; however, until recently, they were almost unknown in seismology. This paper presents several solutions of this kind applied to acoustic modeling for both lossy and lossless media. We evaluated the numerical merits of those methods and provide an estimation of their numerical complexity. In our numerical realization we use the matrix-free implementation of the corresponding integral operator. We study the accuracy of those approximate solutions and demonstrate, that the quasi-analytical approximation is more accurate, than the Born approximation. Further, we apply the quasi-analytical approximation to the solution of the inverse problem. It is demonstrated that, this approach improves the estimation of the data gradient, comparing to the Born approximation. The developed inversion algorithm is based on the conjugate-gradient type optimization. Numerical model study demonstrates that the quasi-analytical solution significantly reduces computation time of the seismic full-waveform inversion. We also show how the quasi-analytical approximation can be extended to the case of elastic wavefield.
3D inverse-opal structured Li4Ti5O12 anode for fast Li-ion storage capabilities
NASA Astrophysics Data System (ADS)
Kim, Dahye; Quang, Nguyen Duc; Hien, Truong Thi; Chinh, Nguyen Duc; Kim, Chunjoong; Kim, Dojin
2017-06-01
Since the demand for high power Li-ion batteries (LIBs) is increasing, spinel-structured lithium titanate, Li4Ti5O12 (LTO), as the anode material has attracted great attention because of its excellent cycle retention, good thermal stability, high rate capability, and so on. However, LTO shows relatively low conductivity due to empty 3d orbital of Ti4+ state. Nanoscale architectures can shorten electron conduction path, thus such low electronic conductivity can be overcome while Li+ can be easily accessed due to large surface area. Herein, three dimensional bicontinuous LTO electrodes were prepared via close-packed self-assembly with polystyrene (PS) spheres followed by removal of them, which leads to no blockage of Li+ ion transportation pathways as well as fast electron conduction. 3D bicontinuous LTO electrodes showed high-rate lithium storage capability (103 mAh/g at 20 C), which is promising as the power sources that require rapid electrochemical response. [Figure not available: see fulltext.
NASA Astrophysics Data System (ADS)
Eberhart-Phillips, Donna; Fry, Bill
2017-08-01
We have developed a joint inversion of surface wave group velocity (U) and local earthquake travel-time (LET) data and applied it to the North Island, New Zealand, to improve the existing New Zealand wide 3-D seismic velocity model. This approach takes full advantage of the differing sensitivities of surface and body waves. The data are complementary, particularly at shallow depths where LET tomography suffers from vertical smearing and surface wave tomography is susceptible to horizontal smearing. The employed U observations are 2-D models at discrete periods which were developed for Rayleigh wave dispersion curves measured from the 1744 interstation Green's Functions obtained by stacked cross-correlations of broadband ambient noise data. In the volume surrounding each U observation, we distribute numerous points for relating the U observation to the gridded 3-D tomography model, analogous to points along a raypath. The partial derivatives at the points are computed using the U sensitivity kernels for Vp and Vs, with Vs related to Vp and Vp/Vs perturbations. Thus, the U observations are included along with the travel-time observations in a joint inversion to best fit the data and the existing tomography model. The resulting model favors the U where there is little travel-time resolution. The combined inversion used 2949 U observations at 6-16 s period and LET from 1509 earthquakes that extend to 370 km depth, and improved the model fit by reducing the U residual data variance by 62% and the LET by 9%. The resulting model generally has better constrained depth of shallow anomalies, with decreased velocity in the upper 2 km in the western North Island, and slight focusing of crustal high velocity features at 8 km depth. Significantly, the increased resolution in the shallowest 5 km of the model improves the utility of the 3-D model for use in seismic hazard assessment, wave propagation studies, and studies comparing seismic velocities to geological mapping.
Chajon, Enrique; Dumas, Isabelle; Touleimat, Mahmoud B.Sc.; Magne, Nicolas; Coulot, Jeremy; Verstraet, Rodolfe; Lefkopoulos, Dimitri; Haie-Meder, Christine
2007-11-01
Purpose: The purpose of this study was to evaluate the inverse planning simulated annealing (IPSA) software for the optimization of dose distribution in patients with cervix carcinoma treated with MRI-based pulsed-dose rate intracavitary brachytherapy. Methods and Materials: Thirty patients treated with a technique using a customized vaginal mold were selected. Dose-volume parameters obtained using the IPSA method were compared with the classic manual optimization method (MOM). Target volumes and organs at risk were delineated according to the Gynecological Brachytherapy Group/European Society for Therapeutic Radiology and Oncology recommendations. Because the pulsed dose rate program was based on clinical experience with low dose rate, dwell time values were required to be as homogeneous as possible. To achieve this goal, different modifications of the IPSA program were applied. Results: The first dose distribution calculated by the IPSA algorithm proposed a heterogeneous distribution of dwell time positions. The mean D90, D100, and V100 calculated with both methods did not differ significantly when the constraints were applied. For the bladder, doses calculated at the ICRU reference point derived from the MOM differed significantly from the doses calculated by the IPSA method (mean, 58.4 vs. 55 Gy respectively; p = 0.0001). For the rectum, the doses calculated at the ICRU reference point were also significantly lower with the IPSA method. Conclusions: The inverse planning method provided fast and automatic solutions for the optimization of dose distribution. However, the straightforward use of IPSA generated significant heterogeneity in dwell time values. Caution is therefore recommended in the use of inverse optimization tools with clinical relevance study of new dosimetric rules.
NASA Astrophysics Data System (ADS)
Chaves, Carlos Alberto Moreno; Ussami, Naomi
2013-12-01
developed a three-dimensional scheme to invert geoid anomalies aiming to map density variations in the mantle. Using an ellipsoidal-Earth approximation, the model space is represented by tesseroids. To assess the quality of the density models, the resolution and covariance matrices were computed. From a synthetic geoid anomaly caused by a plume tail with Gaussian noise added, the inversion code was able to recover a plausible solution about the density contrast and geometry when it is compared to the synthetic model. To test the inversion algorithm in a natural case study, geoid anomalies from the Yellowstone Province (YP) were inverted. From the Earth Gravitational Model 2008 expanded up to degree 2160, lower crust- and mantle-related negative geoid anomalies with amplitude of approximately 70 m were obtained after removing long-wavelength components (>5400 km) and crustal effects. We estimated three density models for the YP. The first model, the EDM-1 (estimated density model), uses a starting model with density contrast equal to 0. The other two models, the EDM-2 and EDM-3, use an initial density derived from two S-velocity models for the western United States, the Dynamic North America Models of S Waves by Obrebsky et al. (2011) and the Northwestern United States Teleseismic Tomography of S Waves (NWUS11-S) by James et al. (2011). In these three models, a lower and an upper bound for the density solution was also imposed as a priori information. Regardless of the initial constraints, the inversion of the residual geoid indicates that the lower crust and the upper mantle of the YP have a predominantly negative density contrast ( -50 kg/m3) relative to the surrounding mantle. This solution reveals that the density contrast extends at least to 660 km depth. Regional correlation analysis between the EDM-1 and NWUS11-S indicates an anticorrelation (coefficient of -0.7) at 400 km depth. Our study suggests that the mantle density derived from the inversion of geoid
Solid-liquid phase transitions in 3D systems with the inverse-power and Yukawa potentials
NASA Astrophysics Data System (ADS)
Vaulina, O. S.; Koss, X. G.
2016-03-01
The melting of face-centered cubic (fcc) and body-centered cubic (bcc) crystal lattices was studied analytically and numerically for the systems of particles interacting via the inverse-power-law and Yukawa potentials. New approach is proposed for determination of the solid-liquid phase transitions in these systems. The suggested approach takes into account a nonlinearity (anharmonicity) of pair interaction forces and allows to correctly predict the conditions of melting of the systems with various isotropic pair interaction potentials. The obtained results are compared with the existing theoretical and numerical data.
NASA Astrophysics Data System (ADS)
Heincke, B.; Moorkamp, M.; Jegen, M.; Hobbs, R. W.
2012-12-01
Imaging of sub-basalt sediments with reflection seismic techniques is limited due to absorption, scattering and transmission effects and the presence of peg-leg multiples. Although many of the difficulties facing conventional seismic profiles can be overcome by recording long offset data resolution of sub-basalt sediments in seismic sections is typically still largely restricted. Therefore multi-parametric approaches in general and joint inversion strategies in particular (e.g. Colombo et al., 2008, Jordan et al., 2012) are considered as alternative to gain additional information from sub-basalt structures. Here, we combine in a 3-D joint inversion first-arrival time tomography, FTG gravity and MT data to identify the base basalt and resolve potential sediments underneath. For sub-basalt exploration the three methods complement each other such that the null space is reduced and significantly better resolved models can be obtained than would be possible by the individual methods: The seismic data gives a robust model for the supra-basalt sediments whilst the gravity field is dominated by the high density basalt and basement features. The MT on the other hand is sensitive to the conductivity in both the supra- and sub-basalt sediments. We will present preliminary individual and joint inversion result for a FTG, seismic and MT data set located in the Faroe-Shetland basin. Because the investigated area is rather large (~75 x 40 km) and the individual data sets are relatively huge, we use a joint inversion framework (see Moorkamp et al., 2011) which is designed to handle large amount of data/model parameters. This program has moreover the options to link the individual parameter models either petrophysically using fixed parameter relationships or structurally using the cross-gradient approach. The seismic data set consists of a pattern of 8 intersecting wide-angle seismic profiles with maximum offsets of up to ~24 km. The 3-D gravity data set (size :~ 30 x 30 km) is
NASA Astrophysics Data System (ADS)
Bertrand, E. A.; Caldwell, G.; Bannister, S. C.; Hill, G.; Bennie, S.
2013-12-01
The Taupo Volcanic Zone (TVZ), located in the central North Island of New Zealand, is a rifted arc that contains more than 20 liquid-dominated high-temperature geothermal systems, which together discharge ~4.2 GW of heat at the surface. The shallow (upper ~500 m) extent of these geothermal systems is marked by low-resistivity, mapped by tens-of-thousands of DC resistivity measurements collected throughout the 1970's and 80's. Conceptual models of heat transport through the brittle crust of the TVZ link these low-resistivity anomalies to the tops of vertically ascending plumes of convecting hydrothermal fluid. Recently, data from a 40-site array of broadband seismometers with ~4 km station spacing, and an array of 270 broadband magnetotelluric (MT) measurements with ~2 km station spacing, have been collected in the south-eastern part of the TVZ in an experiment to image the deep structure (or roots) of the geothermal systems in this region. Unlike DC resistivity, these MT measurements are capable of resolving the resistivity structure of the Earth to depths of 10 km or more. 2-D and 3-D models of subsets of these MT data have been used to provide the first-ever images of quasi-vertical low-resistivity zones (at depths of 3-7 km) that connect with the near-surface geothermal fields. These low-resistivity zones are interpreted to represent convection plumes of high-temperature fluids ascending within fractures, which supply heat to the overlying geothermal fields. At the Rotokawa, Ngatamariki and Ohaaki geothermal fields, these plumes extend to a broad layer of low-resistivity, inferred to represent a magmatic, basal heat source located below the seismogenic zone (at ~7-8 km depth) that drives convection in the brittle crust above. Little is known about the mechanisms that transfer heat into the hydrothermal regime. However, at Rotokawa, new 3-D resistivity models image a vertical low-resistivity zone that lies directly beneath the geothermal field. The top of this
NASA Astrophysics Data System (ADS)
Alqasemi, Redwan; Dubey, Rajiv
2008-04-01
A 9-DoF mobile robotic manipulator system consisting of a 7-DoF redundant manipulator and a differentially driven 2-DoF mobile non-holonomic platform was mathematically modeled to represent a general redundant mobile manipulator. The control of the 3-degree of redundancy system combines the mobility and manipulation, expands on the conventional control methods and introduces user-specified weights to the singularity-robust (S-R) inverse of the Jacobian. Criterion function weight was added to the weight matrix to optimize the control based on joint limit avoidance. A numerical example to apply and compare several control methods was presented. Singularity and joint limit avoidance along with user-defined motion preference were implemented in simulation. Possible applications in defense were explored.
NASA Astrophysics Data System (ADS)
Martin, Roland; Monteiller, Vadim; Chevrot, Sébastien; Wang, Yi; Komatitsch, Dimitri; Dufréchou, Grégory
2015-04-01
We describe here a method of inversion applied to seismic data sets constrained by gravity data at the regional scale. This will allow us to obtain robust models of P and S wave velocities but also of density, providing key constraints on the composition and thermal state of the lithosphere. Our approach relies on teleseimic waves, which illuminate the medium from below. We have developped a hybrid method in which a wave propagation method at the global scale (DSM/Direct solution method) is coupled with a spectral element method at the regional scale (Monteiller et al. 2013). With the spectral element method, we are able to model the 3D wave propagation effects in a computational domain of 400km long x 400km wide and 200 km deep, for an incident teleseismic wavefront introduced at the boundaries of this domain with periods as short as 2 s. The DSM global method allows to compute this incident field for a spherical Earth model. We use a multi-scale joint inversion of both gravity and seismic waveform data, accounting for the long wavelengths of the gravity field taken from a global model. In terms of inversion technique, we have validated an adjoint method for the inversion of seismic waveforms. An optimized BFGS inversion technique is used to minimize the difference between observed and computed full waveforms. The gradient of the misfit function gives the direction over which the model must be perturbed to minimize this difference. At each step of the inversion procedure we choose an optimal step length that accelerates the minimization. This is the crucial ingredient that allows us to build an efficient iterative full waveform inversion. We have extended this method by incorporating gravity data provided by the BGI/Bureau Gravimétrique International into the inversion. If the waveforms allow us to constrain the seismic velocities, they are less sensitive to the structure in density, which gives independent and crucial information to constrain the nature of rocks
NASA Astrophysics Data System (ADS)
Uzkeda, Hodei; Bulnes, Mayte; Poblet, Josep; García-Ramos, José Carlos; Piñuela, Laura
2016-09-01
We constructed a geological map, a 3D model and cross-sections, carried out a structural analysis, determined the stress fields and tectonic transport vectors, restored a cross section and performed a subsidence analysis to unravel the kinematic evolution of the NE emerged portion of the Asturian Basin (NW Iberian Peninsula), where Jurassic rocks crop out. The major folds run NW-SE, normal faults exhibit three dominant orientations: NW-SE, NE-SW and E-W, and thrusts display E-W strikes. After Upper Triassic-Lower Jurassic thermal subsidence, Middle Jurassic doming occurred, accompanied by normal faulting, high heat flow and basin uplift, followed by Upper Jurassic high-rate basin subsidence. Another extensional event, possibly during Late Jurassic-Early Cretaceous, caused an increment in the normal faults displacement. A contractional event, probably of Cenozoic age, led to selective and irregularly distributed buttressing and fault reactivation as reverse or strike-slip faults, and folding and/or offset of some previous faults by new generation folds and thrusts. The Middle Jurassic event could be a precursor of the Bay of Biscay and North Atlantic opening that occurred from Late Jurassic to Early Cretaceous, whereas the Cenozoic event would be responsible for the Pyrenean and Cantabrian ranges and the partial closure of the Bay of Biscay.
Speidel, M; Hatt, C; Tomkowiak, M; Raval, A; Funk, T
2014-06-15
Purpose: To develop a method for the fusion of 3D echocardiography and Scanning-Beam Digital X-ray (SBDX) fluoroscopy to assist with catheter device and soft tissue visualization during interventional procedures. Methods: SBDX is a technology for low-dose inverse geometry x-ray fluoroscopy that performs digital tomosynthesis at multiple planes in real time. In this study, transesophageal echocardiography (TEE) images were fused with SBDX images by estimating the 3D position and orientation (the “pose”) of the TEE probe within the x-ray coordinate system and then spatially transforming the TEE image data to match this pose. An initial pose estimate was obtained through tomosynthesis-based 3D localization of points along the probe perimeter. Position and angle estimates were then iteratively refined by comparing simulated projections of a 3D probe model against SBDX x-ray images. Algorithm performance was quantified by imaging a TEE probe in different known orientations and locations within the x-ray field (0-30 degree tilt angle, up to 50 mm translation). Fused 3D TEE/SBDX imaging was demonstrated by imaging a tissue-mimicking polyvinyl alcohol cylindrical cavity as a catheter was navigated along the cavity axis. Results: Detected changes in probe tilt angle agreed with the known changes to within 1.2 degrees. For a 50 mm translation along the source-detector axis, the detected translation was 50.3 mm. Errors for in-plane translations ranged from 0.1 to 0.9 mm. In a fused 3D TEE/SBDX display, the catheter device was well visualized and coincident with the device shadow in the TEE images. The TEE images portrayed phantom boundaries that were not evident under x-ray. Conclusion: Registration of soft tissue anatomy derived from TEE imaging and device imaging from SBDX x-ray fluoroscopy is feasible. The simultaneous 3D visualization of these two modalities may be useful in interventional procedures involving the navigation of devices to soft tissue anatomy.
NASA Astrophysics Data System (ADS)
An, Zhiguo; Di, Qingyun
2016-12-01
The Alxa area in Inner Mongolia has been selected as a possible site for geological disposal of high-level radioactive waste (HLRW). Based on results of a previous study on crustal stability, the Tamusu rock mass has been chosen as the target. To determine the geological structure of this rock mass, aeromagnetic and gravity data are collected and inverted. Three-dimensional (3D) inversion horizontal slices show that the internal density of the rock mass and the distribution of magnetic properties are not uniform, with fractures and fragmentation being present. To confirm this result, the controlled source audio-frequency magnetotelluric method (CSAMT) was applied to explore the geological structures, the typical CSAMT sounding curve was analyzed, and the response characteristics of the geological structure and surrounding rock are distinguished. The original data were processed and interpreted in combination with data from surface geology and drilling and logging data. It is found that the CSAMT results were consistent with those from 3D inversion of the gravity and magnetic data, confirming the existence of fractures and fragmentation in the exploration area.
NASA Astrophysics Data System (ADS)
Meqbel, N. M.; Egbert, G. D.; Kelbert, A.
2010-12-01
Long period (10-20,000 s) magnetotelluric (MT) data are being acquired in a series of temporary arrays deployed across the continental United States through EMScope, a component of EarthScope, a multidisciplinary decade-long project to study the structure and evolution of the North American Continent. MT deployments in 2006-2010 have so far acquired data at 237 sites on an approximately regular grid, with the same nominal spacing as the USArray broadband seismic transportable array (~70 km), covering the Northwestern US, from the Oregon-Washington coast across the Rocky Mountains, into Montana and Wyoming. Preliminary 3-D inversion results (Patro and Egbert; 2008), based on data from the 110 westernmost “Cascadia” sites collected in the first two years, revealed extensive areas of high conductivity in the lower crust beneath the Northwest Basin and Range (NBR), inferred to result from fluids (including possibly partial melt at depth) associated with magmatic underplating, and beneath the Cascade Mountains, probably due to fluids released by the subducting Juan de Fuca slab. Here we extend this study, refining and further testing the preliminary results from Cascadia, and extending the inversion domain to the East, to include all of the EarthScope data. Although site spacing is very broad, distinct regional structures are clearly evident even in simple maps of apparent resistivity, phase and induction vectors. For the 3-D inversion we are using the parallelized version of our recently developed Modular Code (ModEM), which supports Non-Linear Conjugate Gradient and several Gauss-Newton type schemes. Our initial 3-D inversion results using 212 MT sites, fitting impedances and vertical field transfer functions (together and separately) suggest several conductive and resistive structures which appear to be stable and required by the measured data. These include: - A conductive structure elongated in the N-S direction underneath the volcanic arc of the Cascadia
NASA Astrophysics Data System (ADS)
Llopis-Albert, C.; Capilla, J. E.
2010-09-01
SummaryMajor factors affecting groundwater flow through fractured rocks include the geometry of each fracture, its properties and the fracture-network connectivity together with the porosity and conductivity of the rock matrix. When modelling fractured rocks this is translated into attaining a characterization of the hydraulic conductivity ( K) as adequately as possible, despite its high heterogeneity. This links with the main goal of this paper, which is to present an improvement of a stochastic inverse model, named as Gradual Conditioning (GC) method, to better characterise K in a fractured rock medium by considering different K stochastic structures, belonging to independent K statistical populations (SP) of fracture families and the rock matrix, each one with its own statistical properties. The new methodology is carried out by applying independent deformations to each SP during the conditioning process for constraining stochastic simulations to data. This allows that the statistical properties of each SPs tend to be preserved during the iterative optimization process. It is worthwhile mentioning that so far, no other stochastic inverse modelling technique, with the whole capabilities implemented in the GC method, is able to work with a domain covered by several different stochastic structures taking into account the independence of different populations. The GC method is based on a procedure that gradually changes an initial K field, which is conditioned only to K data, to approximate the reproduction of other types of information, i.e., piezometric head and solute concentration data. The approach is applied to the Äspö Hard Rock Laboratory (HRL) in Sweden, where, since the middle nineties, many experiments have been carried out to increase confidence in alternative radionuclide transport modelling approaches. Because the description of fracture locations and the distribution of hydrodynamic parameters within them are not accurate enough, we address the
Camargo-Junior, Franklin; Ackermann, Marko; Loss, Jefferson F; Sacco, Isabel C N
2013-12-01
The aim of this study was to investigate the effect of errors in the location of the center of pressure (5 and 10 mm) on lower limb joint moment uncertainties at different gait velocities (1.0, 1.5, and 2.0 m/s). Our hypotheses were that the absolute joint moment uncertainties would be gradually reduced from distal to proximal joints and from higher to lower velocities. Joint moments of five healthy young adults were calculated by inverse dynamics using the bottom-up approach, depending on which estimate the uncertainty propagated. Results indicated that there is a linear relationship between errors in center of pressure and joint moment uncertainties. The absolute moment peak uncertainties expressed on the anatomic reference frames decreased from distal to proximal joints, confirming our first hypothesis, except for the abduction moments. There was an increase in moment uncertainty (up to 0.04 N m/kg for the 10 mm error in the center of pressure) from the lower to higher gait velocity, confirming our second hypothesis, although, once again, not for hip or knee abduction. Finally, depending on the plane of movement and the joint, relative uncertainties experienced variation (between 5 and 31%), and the knee joint moments were the most affected.
NASA Astrophysics Data System (ADS)
Sroda, Piotr
2010-05-01
In the area of Trans-European Suture Zone at the East European Craton margin in southeastern Poland (Malopolska and Lysogory Blocks), wide-angle seismic data from CELEBRATION 2000 experiment show strong azimuthal variation of Pg traveltimes and of observed crustal velocity, suggesting considerable anisotropy of the upper crust in this area. The axis of the fast velocity, trending roughly NW-SE, is consistent with the strike of the main tectonic lineaments in Malopolska and Lysogory blocks. Previously published anisotropic model of the crustal structure was based on the delay-time method which allows for robust but simplified calculation of the anisotropy. Current work presents models obtained by three-dimensional tomography with more realistic raytracing and regularized inversion algorithm. The model of a transversally isotropic medium was assumed. To assess credibility of the results, modelling of several subsets of the data was performed, and synthetic tests were carried out to evaluate the spatial resolution of the model. Obtained results confirm existence of substantial upper crustal anisotropy and provide an image of horizontal variability of the anisotropy magnitude in the study area. The result is consistent with the geological structure of the investigated units. In the MB and LB, tightly folded (dip 40-80 deg) metapelitic rocks of Neoproterozoic and younger age occur at depths of few km and deeper, and are likely to cause the observed anisotropy. Fast axis direction coincides well with azimuth of outcropping folds axes and other deformational structures. Therefore, observed anisotropy is interpreted as the effect of collisional deformations at the EEC margin.
NASA Astrophysics Data System (ADS)
Ross, Z.; Ben-Zion, Y.; Zhu, L.; Graves, R. W.
2015-12-01
We perform a full source tensor inversion of several M > 4 earthquakes that occurred in the San Jacinto fault zone in southern California, with an emphasis on resolving signatures of volumetric source changes. A previous study on these events with Green's functions based on a 1D velocity model identified statistically significant explosive isotropic components (Ross et al. 2015). Here we use the SCEC 3D Community Velocity Model to derive Green's functions with source-receiver reciprocity and finite-difference calculations based on the code of Graves (1996). About 50 stations are used at epicentral distances of up to 55 km. The inversions are performed using the 'generalized Cut and Paste' method, which includes CLVD and isotropic components (Zhu and Ben-Zion 2013). The derived source tensors are compared to the results of the previous study based on the simplified 1D velocity model. The results are analyzed with bootstrap analysis to estimate uncertainties involved. Additional tests are performed using synthetic waveforms to study the effects of neglecting various features on the source inversions.
NASA Astrophysics Data System (ADS)
Aucejo, M.; Totaro, N.; Guyader, J.-L.
2010-08-01
In noise control, identification of the source velocity field remains a major problem open to investigation. Consequently, methods such as nearfield acoustical holography (NAH), principal source projection, the inverse frequency response function and hybrid NAH have been developed. However, these methods require free field conditions that are often difficult to achieve in practice. This article presents an alternative method known as inverse patch transfer functions, designed to identify source velocities and developed in the framework of the European SILENCE project. This method is based on the definition of a virtual cavity, the double measurement of the pressure and particle velocity fields on the aperture surfaces of this volume, divided into elementary areas called patches and the inversion of impedances matrices, numerically computed from a modal basis obtained by FEM. Theoretically, the method is applicable to sources with complex 3D geometries and measurements can be carried out in a non-anechoic environment even in the presence of other stationary sources outside the virtual cavity. In the present paper, the theoretical background of the iPTF method is described and the results (numerical and experimental) for a source with simple geometry (two baffled pistons driven in antiphase) are presented and discussed.
NASA Astrophysics Data System (ADS)
Sass, P.; Ritter, O.; Rybin, A.; Batalev, V.
2012-12-01
Many geodynamic processes governing intra-continental collisional orogeny are largely unexplained and controversial. A key question is the state and dynamic behaviour of the lithosphere at middle and lower crustal levels while continental collision progresses. The Pamir - Tien Shan region in Central Asia may be the best location on Earth to study such lithospheric deformation processes in situ. The mountain ranges and high plateaus formed at the tip of the north-western Indian promontory through the Cenozoic experienced rates of shortening similar to the adjacent Himalaya-Tibet system. Today, the Pamir - Tien Shan orogenic belt hosts some of the deepest active intra-continental subduction zones on Earth and absorbs the highest strain rate over the shortest distance that is manifested in the India-Asia collision zone. The multi-disciplinary Tien Shan - Pamir Geodynamic Program (TIPAGE) was designed to address some of the geodynamic key questions in this region. A magnetotelluric (MT) survey was carried out in concert with other geophysical and geological observations in Kyrgyzstan and Tajikistan, predominantly along a 350 km long and 50 km wide corridor from southern Tajikistan to Osh in Kyrgyzstan across the Pamir Plateau and southern Tien Shan mountain ranges. In total we recorded MT data at 178 stations, 26 of them combine long-period and broad band recordings. We present and compare 2D and 3D MT inversion results. Strike analysis of the data revealed an overall mean geo-electric strike direction consistent with the predominant tectonic trends. 2D inversion yields a reasonable data fit, with exception of some sites which exhibit phases above 90 degrees. 3D inversion was carried out with the ModEM package. We inverted for all four impedance tensor components and the vertical magnetic transfer functions. Topography was also included. The 3D models are generally in agreement with the 2D results but achieve a better data fit, particularly phases which could not be
NASA Astrophysics Data System (ADS)
Sass, Paul; Ritter, Oliver; Rybin, Anatolii; Batalev, Vladislav
2013-04-01
Many geodynamic processes governing intra-continental collisional orogeny are largely unexplained and controversial. A key question is the state and dynamic behaviour of the lithosphere at middle and lower crustal levels while continental collision progresses. The Pamir - Tien Shan region in Central Asia may be the best location on Earth to study such lithospheric deformation processes in situ. The mountain ranges and high plateaus formed at the tip of the north-western Indian promontory through the Cenozoic experienced rates of shortening similar to the adjacent Himalaya-Tibet system. Today, the Pamir - Tien Shan orogenic belt hosts some of the deepest active intra-continental subduction zones on Earth and absorbs the highest strain rate over the shortest distance that is manifested in the India-Asia collision zone. The multi-disciplinary Tien Shan - Pamir Geodynamic Program (TIPAGE) was designed to address some of the geodynamic key questions in this region. A magnetotelluric (MT) survey was carried out in concert with other geophysical and geological observations in Kyrgyzstan and Tajikistan, predominantly along a 350 km long and 50 km wide corridor from southern Tajikistan to Osh in Kyrgyzstan across the Pamir Plateau and southern Tien Shan mountain ranges. In total we recorded MT data at 178 stations, 26 of them combine long-period and broad band recordings. We present and compare 2D and 3D MT inversion results. Strike analysis of the data revealed an overall mean geo-electric strike direction consistent with the predominant tectonic trends. 2D inversion yields a reasonable data fit, with exception of some sites which exhibit phases above 90 degrees. 3D inversion was carried out with the ModEM package. We inverted for all four impedance tensor components and the vertical magnetic transfer functions. Topography was also included. The 3D models are generally in agreement with the 2D results but achieve a better data fit, particularly phases which could not be
Oldenburg, Amy L; Yu, Xiao; Gilliss, Thomas; Alabi, Oluwafemi; Taylor, Russell M; Troester, Melissa A
2015-10-20
The progression of breast cancer is known to be affected by stromal cells within the local microenvironment. Here we study the effect of stromal fibroblasts on the in-place motions (motility) of mammary epithelial cells within organoids in 3D co-culture, inferred from the speckle fluctuation spectrum using optical coherence tomography (OCT). In contrast to Brownian motion, mammary cell motions exhibit an inverse power-law fluctuation spectrum. We introduce two complementary metrics for quantifying fluctuation spectra: the power-law exponent and a novel definition of the motility amplitude, both of which are signal- and position-independent. We find that the power-law exponent and motility amplitude are positively (p<0.001) and negatively (p<0.01) correlated with the density of stromal cells in 3D co-culture, respectively. We also show how the hyperspectral data can be visualized using these metrics to observe heterogeneity within organoids. This constitutes a simple and powerful tool for detecting and imaging cellular functional changes with OCT.
Wang, Aijun; Liu, Wenfang; Tang, Junjie; Chen, Sheng-Li; Dong, Peng
2014-04-15
A photonic bandgap (PBG) extension of surface-disordered 3D photonic crystals (PCs) based on the TiO2 inverse opal (TiO2-IO) architecture has been demonstrated. By using a liquid phase deposition (LPD) process based on the controlled hydrolysis of ammonium hexafluorotitanate and boric acid, an extra layer of TiO2 nanoparticles were deposited onto the internal surface of the air voids in the TiO2-IOs to increase their surface roughness, thereby introducing surface disorder in the 3D order structures. The PBG relative width of surface-disordered TiO2-IOs has been broadened significantly, and, compared to the original TiO2-IO, its largest rate of increase (27%) has been obtained. It was found that the PBG relative width increased rapidly at first and then to a much slower rate of change with increase of the duration of the LPD time. A possible cause for this finding is discussed in this Letter.
Oldenburg, Amy L.; Yu, Xiao; Gilliss, Thomas; Alabi, Oluwafemi; Taylor, Russell M.; Troester, Melissa A.
2015-01-01
The progression of breast cancer is known to be affected by stromal cells within the local microenvironment. Here we study the effect of stromal fibroblasts on the in-place motions (motility) of mammary epithelial cells within organoids in 3D co-culture, inferred from the speckle fluctuation spectrum using optical coherence tomography (OCT). In contrast to Brownian motion, mammary cell motions exhibit an inverse power-law fluctuation spectrum. We introduce two complementary metrics for quantifying fluctuation spectra: the power-law exponent and a novel definition of the motility amplitude, both of which are signal- and position-independent. We find that the power-law exponent and motility amplitude are positively (p<0.001) and negatively (p<0.01) correlated with the density of stromal cells in 3D co-culture, respectively. We also show how the hyperspectral data can be visualized using these metrics to observe heterogeneity within organoids. This constitutes a simple and powerful tool for detecting and imaging cellular functional changes with OCT. PMID:26973862
NASA Astrophysics Data System (ADS)
Mashayekhi, Parisa; Ghorbani-Dashtaki, Shoja; Mosaddeghi, Mohammad Reza; Shirani, Hossein; Nodoushan, Ali Reza Mohammadi
2016-04-01
In this study, HYDRUS-2D/3D was used to simulate ponded infiltration through double-ring infiltrometers into a hypothetical loamy soil profile. Twelve scenarios of inverse modelling (divided into three groups) were considered for estimation of Mualem-van Genuchten hydraulic parameters. In the first group, simulation was carried out solely using cumulative infiltration data. In the second group, cumulative infiltration data plus water content at h = -330 cm (field capacity) were used as inputs. In the third group, cumulative infiltration data plus water contents at h = -330 cm (field capacity) and h = -15 000 cm (permanent wilting point) were used simultaneously as predictors. The results showed that numerical inverse modelling of the double-ring infiltrometer data provided a reliable alternative method for determining soil hydraulic parameters. The results also indicated that by reducing the number of hydraulic parameters involved in the optimization process, the simulation error is reduced. The best one in infiltration simulation which parameters α, n, and Ks were optimized using the infiltration data and field capacity as inputs. Including field capacity as additional data was important for better optimization/definition of soil hydraulic functions, but using field capacity and permanent wilting point simultaneously as additional data increased the simulation error.
NASA Astrophysics Data System (ADS)
Martin, Roland; Chevrot, Sébastien; Komatitsch, Dimitri; Seoane, Lucia; Spangenberg, Hannah; Wang, Yi; Dufréchou, Grégory; Bonvalot, Sylvain; Bruinsma, Sean
2017-04-01
We image the internal density structure of the Pyrenees by inverting gravity data using an a priori density model derived by scaling a Vp model obtained by full waveform inversion of teleseismic P-waves. Gravity anomalies are computed via a 3-D high-order finite-element integration in the same high-order spectral-element grid as the one used to solve the wave equation and thus to obtain the velocity model. The curvature of the Earth and surface topography are taken into account in order to obtain a density model as accurate as possible. The method is validated through comparisons with exact semi-analytical solutions. We show that the spectral-element method drastically accelerates the computations when compared to other more classical methods. Different scaling relations between compressional velocity and density are tested, and the Nafe-Drake relation is the one that leads to the best agreement between computed and observed gravity anomalies. Gravity data inversion is then performed and the results allow us to put more constraints on the density structure of the shallow crust and on the deep architecture of the mountain range.
NASA Astrophysics Data System (ADS)
Martin, Roland; Chevrot, Sébastien; Komatitsch, Dimitri; Seoane, Lucia; Spangenberg, Hannah; Wang, Yi; Dufréchou, Grégory; Bonvalot, Sylvain; Bruinsma, Sean
2017-01-01
We image the internal density structure of the Pyrenees by inverting gravity data using an a priori density model derived by scaling a Vp model obtained by full waveform inversion of teleseismic P-waves. Gravity anomalies are computed via a 3D high-order finite-element integration in the same high-order spectral-element grid as the one used to solve the wave equation and thus to obtain the velocity model. The curvature of the Earth and surface topography are taken into account in order to obtain a density model as accurate as possible. The method is validated through comparisons with exact semi-analytical solutions. We show that the spectral element method drastically accelerates the computations when compared to other more classical methods. Different scaling relations between compressional velocity and density are tested, and the Nafe-Drake relation is the one that leads to the best agreement between computed and observed gravity anomalies. Gravity data inversion is then performed and the results allow us to put more constraints on the density structure of the shallow crust and on the deep architecture of the mountain range.
NASA Astrophysics Data System (ADS)
Liang, Q.; Chen, C.; Kaban, M. K.; Thomas, M.
2014-12-01
Mantle density structure is a key for tectonics. The density variations in the upper mantle are affected by temperature and composition. Seismic tomography method has been widely applied to obtain the P- and S-wave velocity structure in the mantle, which is then used to calculate the density perturbation. However, the velocity model is mainly due to the thermal effects but not the compositional effects. A method of 3-D inversion of gravity anomaly developed in spherical coordinates is used to image the large-scale density structure of upper mantle in Southeast Asia. The mantle gravity anomalies used in inversion are calculated by removing the crustal effects from the observed gravity. With constraints of thermal density model from seismic tomography, the integrative density structure is estimated from gravity inversion. Consequently, we obtain the compositional density by subtracting the thermal density from the integrative structure. The result of inversion shows the anisotropic composition of subduction zones, Cratons and plates boundary in Southeast Asia. In the shallow depth, the compositional density anomalies of large scales present uniform features in oceanic and continental mantle. In depth of 75-175 km, there are differences between the thermal and the compositional variations. The density anomalies at these depths are both affected by temperature and composition of the upper mantle. Below 175-km depth, the density anomalies are dominated by the compositional variations. Furthermore, comparing with high seismicity occurred at moderate-depth (50-300 km), we found that the compositional density variations is one of the factor that inducing earthquakes. The constrained inversion of mantle gravity anomaly has possibility to reveal the subduction which is not clearly seen from low-resolution tomography data, and may reveal the relation of seismicity and composition in the upper mantle. This study is supported by the Program of International Science and
NASA Astrophysics Data System (ADS)
Kordy, M.; Wannamaker, P.; Maris, V.; Cherkaev, E.; Hill, G.
2016-01-01
We have developed an algorithm, which we call HexMT, for 3-D simulation and inversion of magnetotelluric (MT) responses using deformable hexahedral finite elements that permit incorporation of topography. Direct solvers parallelized on symmetric multiprocessor (SMP), single-chassis workstations with large RAM are used throughout, including the forward solution, parameter Jacobians and model parameter update. In Part I, the forward simulator and Jacobian calculations are presented. We use first-order edge elements to represent the secondary electric field (E), yielding accuracy O(h) for E and its curl (magnetic field). For very low frequencies or small material admittivities, the E-field requires divergence correction. With the help of Hodge decomposition, the correction may be applied in one step after the forward solution is calculated. This allows accurate E-field solutions in dielectric air. The system matrix factorization and source vector solutions are computed using the MKL PARDISO library, which shows good scalability through 24 processor cores. The factorized matrix is used to calculate the forward response as well as the Jacobians of electromagnetic (EM) field and MT responses using the reciprocity theorem. Comparison with other codes demonstrates accuracy of our forward calculations. We consider a popular conductive/resistive double brick structure, several synthetic topographic models and the natural topography of Mount Erebus in Antarctica. In particular, the ability of finite elements to represent smooth topographic slopes permits accurate simulation of refraction of EM waves normal to the slopes at high frequencies. Run-time tests of the parallelized algorithm indicate that for meshes as large as 176 × 176 × 70 elements, MT forward responses and Jacobians can be calculated in ˜1.5 hr per frequency. Together with an efficient inversion parameter step described in Part II, MT inversion problems of 200-300 stations are computable with total run times
NASA Astrophysics Data System (ADS)
Afonso, J. C.; Fullea, J.; Griffin, W. L.; Yang, Y.; Jones, A. G.; D. Connolly, J. A.; O'Reilly, S. Y.
2013-05-01
of natural mantle samples collected from different tectonic settings (xenoliths, abyssal peridotites, ophiolite samples, etc.). This strategy relaxes more typical and restrictive assumptions such as the use of local/limited xenolith data or compositional regionalizations based on age-composition relations. We demonstrate that the combination of our ρ(m) with a L(m) that exploits the differential sensitivities of specific geophysical observables provides a general and robust inference platform to address the thermochemical structure of the lithosphere and sublithospheric upper mantle. An accompanying paper deals with the integration of these two functions into a general 3-D multiobservable Bayesian inversion method and its computational implementation.
NASA Astrophysics Data System (ADS)
Kardell, Dominik A.
The two end-member concept of mantle plume-driven versus far field stress-driven continental rifting anticipates high volumes of magma emplaced close to the rift-initiating plume, whereas relatively low magmatic volumes are predicted at large distances from the plume where the rifting is thought to be driven by far field stresses. We test this concept at the Guinea Plateau, which represents the last area of separation between Africa and South America, by investigating for rift-related volumes of magmatism using borehole, 3D seismic, and gravity data to run structural 3D inversions in two different data areas. Despite our interpretation of igneous rocks spanning large areas of continental shelf covered by the available seismic surveys, the calculated volumes in the Guinea Plateau barely match the magmatic volumes of other magma-poor margins and thus endorse the aforementioned concept. While the volcanic units on the shelf seem to be characterized more dominantly by horizontally deposited extrusive volcanic flows distributed over larger areas, numerous paleo-seamounts pierce complexly deformed pre and syn-rift sedimentary units on the slope. As non-uniqueness is an omnipresent issue when using potential field data to model geologic features, our method faced some challenges in the areas exhibiting complicated geology. In this situation less rigid constraints were applied in the modeling process. The misfit issues were successfully addressed by filtering the frequency content of the gravity data according to the depth of the investigated geology. In this work, we classify and compare our volume estimates for rift-related magmatism between the Guinea Fracture Zone (FZ) and the Saint Paul's FZ while presenting the refinements applied to our modeling technique.
NASA Astrophysics Data System (ADS)
Afonso, Juan Carlos; Rawlinson, Nicholas; Yang, Yingjie; Schutt, Derek L.; Jones, Alan G.; Fullea, Javier; Griffin, William L.
2016-10-01
We apply a novel 3-D multiobservable probabilistic tomography method that we have recently developed and benchmarked, to directly image the thermochemical structure of the Colorado Plateau and surrounding areas by jointly inverting P wave and S wave teleseismic arrival times, Rayleigh wave dispersion data, Bouguer anomalies, satellite-derived gravity gradients, geoid height, absolute (local and dynamic) elevation, and surface heat flow data. The temperature and compositional structures recovered by our inversion reveal a high level of correlation between recent basaltic magmatism and zones of high temperature and low Mg# (i.e., refertilized mantle) in the lithosphere, consistent with independent geochemical data. However, the lithospheric mantle is overall characterized by a highly heterogeneous thermochemical structure, with only some features correlating well with either Proterozoic and/or Cenozoic crustal structures. This suggests that most of the present-day deep lithospheric architecture reflects the superposition of numerous geodynamic events of different scale and nature to those that created major crustal structures. This is consistent with the complex lithosphere-asthenosphere system that we image, which exhibits a variety of multiscale feedback mechanisms (e.g., small-scale convection, magmatic intrusion, delamination, etc.) driving surface processes. Our results also suggest that most of the present-day elevation in the Colorado Plateau and surrounding regions is the result of thermochemical buoyancy sources within the lithosphere, with dynamic effects (from sublithospheric mantle flow) contributing only locally up to ˜15-35%.
Al-Ashmouny, Khaled M; Chang, Sun-Il; Yoon, Euisik
2012-10-01
We report an analog front-end prototype designed in 0.25 μm CMOS process for hybrid integration into 3-D neural recording microsystems. For scaling towards massive parallel neural recording, the prototype has investigated some critical circuit challenges in power, area, interface, and modularity. We achieved extremely low power consumption of 4 μW/channel, optimized energy efficiency using moderate inversion in low-noise amplifiers (K of 5.98 × 10⁸ or NEF of 2.9), and minimized asynchronous interface (only 2 per 16 channels) for command and data capturing. We also implemented adaptable operations including programmable-gain amplification, power-scalable sampling (up to 50 kS/s/channel), wide configuration range (9-bit) for programmable gain and bandwidth, and 5-bit site selection capability (selecting 16 out of 128 sites). The implemented front-end module has achieved a reduction in noise-energy-area product by a factor of 5-25 times as compared to the state-of-the-art analog front-end approaches reported to date.
NASA Astrophysics Data System (ADS)
Suzuki, W.; Aoi, S.; Maeda, T.; Sekiguchi, H.; Kunugi, T.
2013-12-01
Source inversion analysis using near-source strong-motion records with an assumption of 1-D underground structure models has revealed the overall characteristics of the rupture process of the 2011 Tohoku-Oki mega-thrust earthquake. This assumption for the structure model is acceptable because the seismic waves radiated during the Tohoku-Oki event were rich in the very-low-frequency contents lower than 0.05 Hz, which are less affected by the small-scale heterogeneous structure. The analysis using more reliable Green's functions even in the higher-frequency range considering complex structure of the subduction zone will illuminate more detailed rupture process in space and time and the transition of the frequency dependence of the wave radiation for the Tohoku-Oki earthquake. In this study, we calculate the near-source Green's functions using a 3-D underground structure model and perform the source inversion analysis using them. The 3-D underground structure model used in this study is the Japan Integrated Velocity Structure Model (Headquarters for Earthquake Research Promotion, 2012). A curved fault model on the Pacific plate interface is discretized into 287 subfaults at ~20 km interval. The Green's functions are calculated using GMS (Aoi et al., 2004), which is a simulation program package for the seismic wave field by the finite difference method using discontinuous grids (Aoi and Fujiwara, 1999). Computational region is 136-146.2E in longitude, 34-41.6N in latitude, and 0-100 km in depth. The horizontal and vertical grid intervals are 200 m and 100 m, respectively, for the shallower region and those for the deeper region are tripled. The number of the total grids is 2.1 billion. We derive 300-s records by calculating 36,000 steps with a time interval of 0.0083 second (120 Hz sampling). It takes nearly one hour to compute one case using 48 Graphics Processing Units (GPU) on TSUBAME2.0 supercomputer owned by Tokyo Institute of Technology. In total, 574 cases are
NASA Astrophysics Data System (ADS)
Macquet, Marie; Paul, Anne; Pedersen, Helle A.; Villaseñor, Antonio; Chevrot, Sébastien; Sylvander, Matthieu; Wolyniec, David; Pyrope Working Group
2014-10-01
The lithospheric architecture of the Pyrenees is still uncertain and highly debated. Here, we provide new constraints from a high-resolution 3-D S-wave velocity model of the Pyrenees and the adjacent foreland basins. This model is obtained from ambient noise tomography on records of temporary and permanent seismic arrays installed in southwestern France and northern Spain. We first computed group velocity maps for Rayleigh waves in the 5 to 55 s period range using noise correlation stacks at 1500-8500 station pairs. As the crust is very heterogeneous, poor results were obtained using a single starting model in a linearized inversion of group velocity dispersion curves for the shear wave structure. We therefore built a starting model for each grid node by full exploration of the model space. The resulting 3-D shear wave velocity model is compared to data from previous geophysical studies as a validation test. Despite the poor sensitivity of surface waves to seismic discontinuities, the geometry of the top of the basement and the Moho depth are retrieved well, except along the Cantabrian coast. Major reflectors of the ECORS deep seismic sounding profiles in the central and western Pyrenees coincide with sharp velocity gradients in our velocity model. We retrieve the difference between the thicker Iberian crust and the thinner European crust, the presence of low-velocity material of the Iberian crust underthrust beneath the European crust in the central Pyrenees, and the structural dissymmetry between the South Pyrenean Zone and the North Pyrenean Zone at the shallow crustal level. In the Labourd-Mauléon-Arzacq region (western Pyrenees), there is a high S-wave velocity anomaly at 20-30 km in depth, which might explain the positive Bouguer anomaly of the Labourd Massif. This high-velocity lower crust, which is also detected beneath the Parentis area, might be an imprint of the Albian-Aptian rifting phase. The southeastern part of the Massif Central has an unusual
NASA Astrophysics Data System (ADS)
Suzuki, Yuki; Kawai, Kenji; Geller, Robert J.; Borgeaud, Anselme F. E.; Konishi, Kensuke
2016-12-01
We conduct waveform inversion to infer the three-dimensional (3-D) S-velocity structure in the lowermost 400 km of the mantle (the D'' region) beneath the Northern Pacific region. Our dataset consists of about 20,000 transverse component broadband body-wave seismograms observed at North American stations for 131 intermediate and deep earthquakes which occurred beneath the western Pacific subduction region. We use S, ScS, and other phases that arrive between them. Resolution tests indicate that our methods and dataset can resolve the velocity structure in the target region with a horizontal scale of about 150 km and a vertical scale of about 50 km. The 3-D S-velocity model obtained in this study shows three prominent features: (1) prominent sheet-like lateral high-velocity anomalies up to ˜3% faster than the Preliminary Reference Earth Model (PREM) with a thickness of ˜200 km, whose lower boundary is ˜150 km above the core-mantle boundary (CMB). (2) A prominent low-velocity anomaly block located to the west of the Kamchatka peninsula, which is ˜2.5% slower than PREM, immediately above the CMB beneath the high-velocity anomalies. (3) A relatively thin (˜300 km) low-velocity structure continuous from the low-velocity anomaly "(2)" to at least 400 km above the CMB. We also detect a continuous low-velocity anomaly from the east of the Kamchatka peninsula at an altitude of 50 km above the CMB to the far east of the Kuril islands at an altitude of 400 km above the CMB. We interpret these features respectively as: (1) remnants of slab material where the bridgmanite to Mg-post-perovskite phase transition may have occurred within the slab, (2, 3) large amounts of hot and less dense materials beneath the cold Kula or Pacific slab remnants just above the CMB which ascend and form a passive plume upwelling at the edge of the slab remnants.[Figure not available: see fulltext.
NASA Astrophysics Data System (ADS)
Castineira, D.; Jha, B.; Juanes, R.
2016-12-01
Carbon Capture and Sequestration (CCS) is regarded as a promising technology to mitigate rising CO2 concentrations in the atmosphere from industrial emissions. However, as a result of the inherent uncertainty that is present in geological structures, assessing the stability of geological faults and quantifying the potential for induced seismicity is a fundamental challenge for practical implementation of CCS. Here we present a formal framework for the solution of the inverse problem associated with coupled flow and geomechanics models of CO2 injection and subsurface storage. Our approach builds from the application of Gaussian Processes, MCMC and posterior predictive analysis to evaluate relevant earthquake attributes (earthquake time, location and magnitude) in 3D synthetic models of CO2 storage under geologic, observational and operational uncertainty. In our approach, we first conduct hundreds of simulations of a high-fidelity 3D computational model for CO2 injection into a deep saline aquifer, dominated by an anticline structure and a fault. This ensemble of realizations accounts for uncertainty in the model parameters (including fault geomechanical and rock properties) and observations (earthquake time, location and magnitude). We apply Gaussian processes (GP) to generate a valid surrogate that closely approximates the behavior of the high fidelity (and computationally intensive) model, and apply hyperparameter optimization and cross-validation techniques in the solution of this multidimensional data-fit problem. The net result of this process is the generation of a fast model that can be effectively used for Bayesian analysis. We then implement Markov chain Monte Carlo (MCMC) to determine the posterior distribution of the model uncertain parameters (given some prior distributions for those parameters and given the likelihood defined in this case by the GP model). Our results show that the resulting posterior distributions correctly converge towards the "true
NASA Astrophysics Data System (ADS)
Widiwijayanti, C.; Tiberi, C.; Diament, M.; Deplus, C.; Mikhailov, V.; Louat, R.; Tikhotsky, S.; Gvishiani, A.
2003-04-01
The Molucca Sea extending from northeastern Indonesia to southern Philippines islands, is a zone of oceanic basin closure between two opposite-facing subduction zones. This convergence results in the collision of two subduction zones, which style evolves from the southern to the northern parts of the Molucca Sea. In order to provide new insights into the present-day lithospheric structures in the Molucca Sea area, we inverted satellite and sea-surface gravity data into an iterative scheme including a priori seismological data. The seismological data were collected from two networks of Ocean Bottom Seismometer (OBS). These data allowed us to locate local seismic events and to build 3D tomographic images. We relate these results to the different stages of collision. The gravity data consists of combined sea-surface and satellite derived gravity. We used Kolmogorov-Wiener optimal (mean-square) filter to extract the gravity signal associated with lithospheric structures, then analyzed it to determine main regional features of lithospheric structure. For this purpose we employed a selection of Euler solutions based on a new clustering technique. To identify the geometry and nature of lithospheric structures, we also performed a 3-D gravity inversion for the northern Molucca Sea data, introducing our tomographic model as an independent constraint. The combination of both methods permits us to obtain a coherent image of the lithospheric structure. The results of this study illustrate the heterogeneity of lithospheric units in the northern Molucca Sea, which results from the collision between the Sangihe margin and lithospheric fragments from the Phillipine plate such as the Snellius plateau or the Halmahera volcanic arc. Three phenomena can explain the observed lithospheric structure: 1) the rupture of the Molucca Sea plate, accompanied by the appearance at the surface of slices of oceanic crust, favoring the development of suture zones as the collision evolves, 2) the
NASA Astrophysics Data System (ADS)
Pilia, S.; Rawlinson, N.; Direen, N. G.
2013-12-01
Although the notion of Rodinia is quite well accepted in the geoscience community, the location and nature of the eastern continental margin of the Gondwana fragment in Australia is still vague and remains one of the most hotly debated topics in Australian geology. Moreover, most post-Rodinian reconstructions models choose not to tackle the ';Tasmanian challenge', and focus only on the tectonic evolution of mainland southeast Australia, thereby conveniently ignoring the wider tectonic implications of Tasmania's complex geological history. One of the chief limitations of the tectonic reconstructions in this region is a lack of information on Paleozoic (possibly Proterozoic) basement structures. Vast Mesozoic-Cainozoic sedimentary and volcanic cover sequences obscure older outcrops and limit the power of direct observational techniques. In response to these challenges, our effort is focused on ambient seismic noise for imaging 3D crustal shear velocity structure using surface waves, which is capable of illuminating basement structure beneath younger cover. The data used in this study is sourced from the WOMBAT transportable seismic array, which is compounded by around 650 stations spanning the majority of southeastern Australia, including Tasmania and several islands in Bass Strait. To produce the highest quality Green's functions, careful processing of the data has been performed, after which group velocity dispersion measurements have been carried out using a frequency-time analysis method on the symmetric component of the empirical Green's functions (EGFs). Group dispersion measurements from the EGFs have been inverted using a novel hierarchical, transdimensional, Bayesian algorithm to obtain Rayleigh-wave group velocity maps at different periods from 2 to 30 s. The new approach has several advantages in that the number and distribution of model parameters are implicitly controlled by the data, in which the noise is treated as unknown in the inversion. This
NASA Astrophysics Data System (ADS)
Balvert, Marleen; van Hoof, Stefan J.; Granton, Patrick V.; Trani, Daniela; den Hertog, Dick; Hoffmann, Aswin L.; Verhaegen, Frank
2015-07-01
Advances in precision small animal radiotherapy hardware enable the delivery of increasingly complicated dose distributions on the millimeter scale. Manual creation and evaluation of treatment plans becomes difficult or even infeasible with an increasing number of degrees of freedom for dose delivery and available image data. The goal of this work is to develop an optimisation model that determines beam-on times for a given beam configuration, and to assess the feasibility and benefits of an automated treatment planning system for small animal radiotherapy. The developed model determines a Pareto optimal solution using operator-defined weights for a multiple-objective treatment planning problem. An interactive approach allows the planner to navigate towards, and to select the Pareto optimal treatment plan that yields the most preferred trade-off of the conflicting objectives. This model was evaluated using four small animal cases based on cone-beam computed tomography images. Resulting treatment plan quality was compared to the quality of manually optimised treatment plans using dose-volume histograms and metrics. Results show that the developed framework is well capable of optimising beam-on times for 3D dose distributions and offers several advantages over manual treatment plan optimisation. For all cases but the simple flank tumour case, a similar amount of time was needed for manual and automated beam-on time optimisation. In this time frame, manual optimisation generates a single treatment plan, while the inverse planning system yields a set of Pareto optimal solutions which provides quantitative insight on the sensitivity of conflicting objectives. Treatment planning automation decreases the dependence on operator experience and allows for the use of class solutions for similar treatment scenarios. This can shorten the time required for treatment planning and therefore increase animal throughput. In addition, this can improve treatment standardisation and
NASA Astrophysics Data System (ADS)
Favier, L.; Zwinger, T.; Gillet-Chaulet, F.; Durand, G.; Gagliardini, O.
2012-04-01
Ice discharge and grounding line retreat in West Antarctica have been accelerated during the last decades. One of the most striking example is Pine Island Glacier (PIG) which accelerated dramatically over the last 30 years. Such rapid changes in this part of Antarctica are due to large modifications of ice dynamics which are nevertheless poorly understood, and badly represented in numerical models, as pointed out by the IPCC fourth assessment report. Here, a 3D full-Stokes model of a marine ice sheet is used to carry out prognostic simulations of PIG over the next two centuries. The flow problem is coupled with the evolution of the upper and lower free surfaces, and the position of the grounding line is determined by solving the contact problem between the ice-shelf/ice-sheet lower surface and the bedrock. The upper and lower surfaces, and the bathymetry provided on a 1 km grid (courtesy of A. Le Brocq) are used to produce the initial geometry of the entire PIG basin. The mesh refinement is a function of the surface velocities (also provided on a 1 km grid by A. Le Brocq) Hessian matrix and the distance to the grounding line. Surface velocities are also used to infer the basal drag through the resolution of an inverse Robin problem. The initial surface is first relaxed and the results are compared to the observed current surface elevation, surface velocity and change in surface elevation. A perturbation experiment is then performed for which the whole ice-shelf is instantaneously removed. This test can be seen as a worst case scenario as all the buttressing induced by the ice shelf is lost instantaneously. The effect of the ice-shelf disintegration for the following two centuries is discussed in terms of grounding line retreat and increase in sea level.
NASA Astrophysics Data System (ADS)
Lebedeva-Ivanova, Nina; Gaina, Carmen; Minakov, Alexander; Kashubin, Sergey
2016-04-01
We derived Moho depth and crustal thickness for the High Arctic region by 3D forward and inverse gravity modelling method in the spectral domain (Minakov et al. 2012) using lithosphere thermal gravity anomaly correction (Alvey et al., 2008); a vertical density variation for the sedimentary layer and lateral crustal variation density. Recently updated grids of bathymetry (Jakobsson et al., 2012), gravity anomaly (Gaina et al, 2011) and dynamic topography (Spasojevic & Gurnis, 2012) were used as input data for the algorithm. TeMAr sedimentary thickness grid (Petrov et al., 2013) was modified according to the most recently published seismic data, and was re-gridded and utilized as input data. Other input parameters for the algorithm were calibrated using seismic crustal scale profiles. The results are numerically compared with publically available grids of the Moho depth and crustal thickness for the High Arctic region (CRUST 1 and GEMMA global grids; the deep Arctic Ocean grids by Glebovsky et al., 2013) and seismic crustal scale profiles. The global grids provide coarser resolution of 0.5-1.0 geographic degrees and not focused on the High Arctic region. Our grids better capture all main features of the region and show smaller error in relation to the seismic crustal profiles compare to CRUST 1 and GEMMA grids. Results of 3D gravity modelling by Glebovsky et al. (2013) with separated geostructures approach show also good fit with seismic profiles; however these grids cover the deep part of the Arctic Ocean only. Alvey A, Gaina C, Kusznir NJ, Torsvik TH (2008). Integrated crustal thickness mapping and plate recon-structions for the high Arctic. Earth Planet Sci Lett 274:310-321. Gaina C, Werner SC, Saltus R, Maus S (2011). Circum-Arctic mapping project: new magnetic and gravity anomaly maps of the Arctic. Geol Soc Lond Mem 35, 39-48. Glebovsky V.Yu., Astafurova E.G., Chernykh A.A., Korneva M.A., Kaminsky V.D., Poselov V.A. (2013). Thickness of the Earth's crust in the
Structure-, stratigraphy- and fault-guided regularization in geophysical inversion
NASA Astrophysics Data System (ADS)
Wu, Xinming
2017-07-01
Geophysical inversion is often ill-posed because of inaccurate and insufficient data. Regularization is often applied to the inversion problem to obtain a stable solution by imposing additional constraints on the model. Common regularization schemes impose isotropic smoothness on solutions and may have difficulties in obtaining geologically reasonable models that are often supposed to be anisotropic and conform to subsurface structural and stratigraphic features. I introduce a general method to incorporate constraints of seismic structural and stratigraphic orientations and fault slips into geophysical inversion problems. I first use a migrated seismic image to estimate structural and stratigraphic orientations and fault slip vectors that correlate fault blocks on opposite sides of a fault. I then use the estimated orientations and fault slips to construct simple and convenient anisotropic regularization operators in inversion problems to spread information along structural and stratigraphic orientations and across faults. In this way, we are able to compute inverted models that conform to seismic reflectors, faults and stratigraphic features such as channels. The regularization is also helpful to integrate well-log properties into the inversion by spreading the measured rock properties away from the well-log positions into the whole inverted model across faults and along structural and stratigraphic orientations. I use a 3-D synthetic example of impedance inversion to illustrate the structure-, stratigraphy- and fault-guided regularization method. I further applied the method to estimate seismic interval velocity and to compute structure- and stratigraphy-oriented semblance.
Directional structure tensors in estimating seismic structural and stratigraphic orientations
NASA Astrophysics Data System (ADS)
Wu, Xinming; Janson, Xavier
2017-07-01
Estimating orientations of seismic structures (reflections) and stratigraphic features (channels) is important for seismic interpretation, subsurface interpolation and geophysical inversion. Structure tensors, constructed as smoothed outer products of amplitude gradients, are commonly used to estimate seismic reflection normals, which uniquely define the reflection orientations. However, this conventional structure-tensor method often generates significant errors in estimating orientations of the reflections with steep and rapidly varying slopes. To better estimate reflection orientations, we propose to construct structure tensors in a new space, where the reflections are mostly flat or only slightly dipping and the variation of reflection slopes is reduced. We use these constructed structure tensors to compute reflection normals in this new space and then transform the normals back to obtain a better estimation of reflection orientations in the original space. Seismic stratigraphic features such as channels are often aligned within dipping reflections. It is not discussed previously by others to estimate orientations of such features directly from a seismic image. An ideal way to estimate stratigraphic orientations is to first extract a horizon surface with stratigraphic features, and then construct structure tensors with gradients on the surface to estimate the orientations of the features. However, extracting horizon surfaces can be a difficult and time-consuming task in practice. Fortunately, computing gradients on a horizon surface is only a local operation and is equivalent to directly compute directional derivatives along reflection slopes without picking horizons. Based on this observation, we propose to use an equivalent but more efficient way to estimate seismic stratigraphic orientations by using structure tensors constructed with the directional derivatives along reflections. We demonstrate the methods of estimating structural and stratigraphic
NASA Astrophysics Data System (ADS)
Chen, Y. L.; Wu, J. C.; Guo, L. Y.; Wang, X. Y.; Tan, H. B.; Shen, C. Y.
2015-08-01
Conventional D-InSAR (Differential SAR Interferometry) can only monitor 1-D surface deformation along LOS (line of sight) direction. In order to overcome this limitation and extract 3-D coseismic displacement, we combine the LOS displacement derived from D-InSAR technology, the OKADA elastic half space dislocation model theory, jointly the surface rupture distribution by field investigations and the fault model inverted by GPS, level data and gravity survey to retrieve the directions of surface co-seismic displacement, and then have got Wenchuan Ms8.0 Earthquake 3D displacement. Firstly, thirty six L-band PALSAR images of six adjacent ascending tracks are processed with D-InSAR technology to obtain the coseismic displacements along LOS direction. According to the OKADA model and the thrust fault movement model of the Long-Men-Shan Fault , we specify the three directions of surface coseismic displacements. And thus the 3D coseismic displacement field is then recovered by using LOS displacement and relevant geometric projection formulas, obviously including horizontal displacements field and vertical deformation contour maps. By comparing with the 3D displacement estimated from OKADA dislocation model and fault model, the displacement retrieved in this study can give more detail, and reflect seismic characteristics more truly.
Naganawa, Shinji; Ishihara, Shunichi; Iwano, Shingo; Sone, Michihiko; Nakashima, Tsutomu
2010-01-01
To enable volume visualization of endolymphatic hydrops of Ménière's disease via a volume rendering (VR) technique, a three-dimensional (3D) inversion-recovery (IR) sequence with real reconstruction (3D-real IR) sequence after intratympanic injection of Gd-DTPA was optimized for higher spatial resolution using a 32-channel head coil at 3T. Pulse sequence parameters were optimized using a diluted Gd-DTPA phantom. Then, 11 patients who had been clinically diagnosed with Ménière's disease and a patient with sudden hearing loss were scanned. Images were processed using commercially available 3D-VR software. 3D-real IR data was processed to produce endolymph and perilymph fluid volume images in different colors. 3D-CISS data was processed to generate total fluid volume images. While maintaining a comparable signal-to-noise ratio (SNR) and scan time, the voxel volume could be reduced from 0.4 x 0.4 x 2 mm(3) with a 12-channel coil to 0.4 x 0.4 x 0.8 mm(3) with a 32-channel coil. A newly-optimized protocol allowed the smooth, three-dimensional visualization of endolymphatic hydrops in all patients with Ménière's disease. Volumetrically separate visualization of endo-/perilymphatic space is now feasible in patients with Ménière's disease using an optimized 3D-real IR sequence, a 32-channel head coil, at 3T, after intratympanic administration of Gd-DTPA. This will aid the understanding of the pathophysiology of Ménière's disease. (c) 2009 Wiley-Liss, Inc.
NASA Astrophysics Data System (ADS)
Kreeprasertkul, Kritti
Joint PP and SS seismic inversion is a geophysical analysis method that uses the variation in reflectivity of PP and SS seismic data to derive elastic properties of the subsurface and specifically reservoir properties. The major objective of this research is to characterize the elastic properties of the Bakken petroleum system at Banner Field, Mountrail County, North Dakota using joint PP and SS seismic inversion. The combination of PP and SS data into the inversion process helped improve the accuracy of inversion results by increasing the correlation coefficient by 10 percent on both P- and S- impedance. Results from this analysis show a variation in elastic properties from the western part to the eastern portion of the study area. The western part is interpreted to be higher in shale volume, porosity and maturity. Additionally, the natural fracture network is an integral part of a tight oil reservoir. The existence and delineation of natural fractures coincides with faults that have been delineated within the reservoir interval. The elastic parameters and structural detailing from this study has been used to delineate a potential exploration opportunity in the Three Forks Formation on the west side of the survey.
Rutz, Tobias; Piccini, Davide; Coppo, Simone; Chaptinel, Jerome; Ginami, Giulia; Vincenti, Gabriella; Stuber, Matthias; Schwitter, Juerg
2016-12-01
The border zone of post-infarction myocardial scar as identified by late gadolinium enhancement (LGE) has been identified as a substrate for arrhythmias and consequently, high-resolution 3D scar information is potentially useful for planning of electrophysiological interventions. This study evaluates the performance of a novel high-resolution 3D self-navigated free-breathing inversion recovery magnetic resonance pulse sequence (3D-SN-LGE) vs. conventional 2D breath-hold LGE (2D-LGE) with regard to sharpness of borders (SBorder) of post-infarction scar. Patients with post-infarction scar underwent two magnetic resonance examinations for conventional 2D-LGE and high-resolution 3D-SN-LGE acquisitions (both 15 min after 0.2 mmol/kg Gadobutrol IV) at 1.5T. In the prototype 3D-SN-LGE sequence, each ECG-triggered radial steady-state-free-precession read-out segment is preceded by a non-slice-selective inversion pulse. Scar volume and SBorder were assessed on 2D-LGE and matching reconstructed high-resolution 3D-SN-LGE short-axis slices. In 16 patients (four females, 58 ± 10y) all scars visualized by 2D-LGE could be identified on 3D-SN-LGE (time between 2D-LGE and 3D-SN-LGE 48 ± 53 days). A good agreement of scar volume by 3D-SN-LGE vs. 2D-LGE was found (Bland-Altman: -3.7 ± 3.4 ml, correlation: r = 0.987, p < 0.001) with a small difference in scar volume (20.5 (15.8, 35.2) ml vs. 24.5 (20.0, 41.9)) ml, respectively, p = 0.002] and a good intra- and interobserver variability (1.1 ± 4.1 and -1.1 ± 11.9 ml, respectively). SBorder of border "scar to non-infarcted myocardium" was superior on 3D-SN-LGE vs. 2D-LGE: 0.180 ± 0.044 vs. 0.083 ± 0.038, p < 0.001. Detection and quantification of myocardial scar by 3D-SN-LGE is feasible and accurate in comparison to 2D-LGE. The high spatial resolution of the 3D sequence improves delineation of scar borders.
NASA Astrophysics Data System (ADS)
Marinin, I. V.; Kabanikhin, S. I.; Krivorotko, O. I.; Karas, A.; Khidasheli, D. G.
2012-04-01
We consider new techniques and methods for earthquake and tsunami related problems, particularly - inverse problems for the determination of tsunami source parameters, numerical simulation of long wave propagation in soil and water and tsunami risk estimations. In addition, we will touch upon the issue of database management and destruction scenario visualization. New approaches and strategies, as well as mathematical tools and software are to be shown. The long joint investigations by researchers of the Institute of Mathematical Geophysics and Computational Mathematics SB RAS and specialists from WAPMERR and Informap have produced special theoretical approaches, numerical methods, and software tsunami and earthquake modeling (modeling of propagation and run-up of tsunami waves on coastal areas), visualization, risk estimation of tsunami, and earthquakes. Algorithms are developed for the operational definition of the origin and forms of the tsunami source. The system TSS numerically simulates the source of tsunami and/or earthquakes and includes the possibility to solve the direct and the inverse problem. It becomes possible to involve advanced mathematical results to improve models and to increase the resolution of inverse problems. Via TSS one can construct maps of risks, the online scenario of disasters, estimation of potential damage to buildings and roads. One of the main tools for the numerical modeling is the finite volume method (FVM), which allows us to achieve stability with respect to possible input errors, as well as to achieve optimum computing speed. Our approach to the inverse problem of tsunami and earthquake determination is based on recent theoretical results concerning the Dirichlet problem for the wave equation. This problem is intrinsically ill-posed. We use the optimization approach to solve this problem and SVD-analysis to estimate the degree of ill-posedness and to find the quasi-solution. The software system we developed is intended to
NASA Astrophysics Data System (ADS)
Zhou, Li; Zhang, Wei; Shen, Yang; Chen, Xiaofei; Zhang, Jie
2016-06-01
With dense seismic arrays and advanced imaging methods, regional three-dimensional (3D) Earth models have become more accurate. It is now increasingly feasible and advantageous to use a 3D Earth model to better locate earthquakes and invert their source mechanisms by fitting synthetics to observed waveforms. In this study, we develop an approach to determine both the earthquake location and source mechanism from waveform information. The observed waveforms are filtered in different frequency bands and separated into windows for the individual phases. Instead of picking the arrival times, the traveltime differences are measured by cross-correlation between synthetic waveforms based on the 3D Earth model and observed waveforms. The earthquake location is determined by minimizing the cross-correlation traveltime differences. We then fix the horizontal location of the earthquake and perform a grid search in depth to determine the source mechanism at each point by fitting the synthetic and observed waveforms. This new method is verified by a synthetic test with noise added to the synthetic waveforms and a realistic station distribution. We apply this method to a series of M W3.4-5.6 earthquakes in the Longmenshan fault (LMSF) zone, a region with rugged topography between the eastern margin of the Tibetan plateau and the western part of the Sichuan basin. The results show that our solutions result in improved waveform fits compared to the source parameters from the catalogs we used and the location can be better constrained than the amplitude-only approach. Furthermore, the source solutions with realistic topography provide a better fit to the observed waveforms than those without the topography, indicating the need to take the topography into account in regions with rugged topography.
ERIC Educational Resources Information Center
Brown, Malcolm
2009-01-01
Inversions are fascinating phenomena. They are reversals of the normal or expected order. They occur across a wide variety of contexts. What do inversions have to do with learning spaces? The author suggests that they are a useful metaphor for the process that is unfolding in higher education with respect to education. On the basis of…
ERIC Educational Resources Information Center
Brown, Malcolm
2009-01-01
Inversions are fascinating phenomena. They are reversals of the normal or expected order. They occur across a wide variety of contexts. What do inversions have to do with learning spaces? The author suggests that they are a useful metaphor for the process that is unfolding in higher education with respect to education. On the basis of…
Walroth, Richard C; Lukens, James T; MacMillan, Samantha N; Finkelstein, Kenneth D; Lancaster, Kyle M
2016-02-17
The contested electronic structure of [Cu(CF3)4](1-) is investigated with UV/visible/near IR spectroscopy, Cu K-edge X-ray absorption spectroscopy, and 1s2p resonant inelastic X-ray scattering. These data, supported by density functional theory, multiplet theory, and multireference calculations, support a ground state electronic configuration in which the lowest unoccupied orbital is of predominantly trifluoromethyl character. The consensus 3d(10) configuration features an inverted ligand field in which all five metal-localized molecular orbitals are located at lower energy relative to the trifluoromethyl-centered σ orbitals.
2008-09-01
nonunique properties of inversion methods, we may often find a solution for one data type, but we must acknowledge that, although it can predict behavior...of density prisms and a suite of 1D fundamental mode group velocities. (a) A single cell with its input geographic coordinate system . (b) For a...H. K., H. Kanamori, P. C. Jennings, and C. Kissling (Eds.) (2002). International Handbook of Earthquake and Engineering Seismology (CD-ROM
NASA Astrophysics Data System (ADS)
Cárdenas-Soto, M.; Tejero, A.; Nava-Flores, M.; Zenil, D. E.; Vidal-Garcia, M.; Garcia-Serrano, A.
2016-12-01
In this work we build 3D Vs models using seismic tomography of ambient noise. The goal is to characterize the subsurface structure in order to explore the causes of a sudden mine collapse in the 2nd section of Chapultepec park, Mexico City, near to a recreation lake whose subsoil is composed of vulcano-sedimentary materials that were economically exploited in the mid-20th century, leaving a series of underground mines that were rehabilitated for the construction of the Park. In this site we record ambient noise continuously at a 250 Hz sampling rate by intervals of 30 min in three arrays of quadrangular shape with 64 - 4.5 Hz vertical geophones separated 2m. In order to confront the seismic interferometry results, we also obtain 3D models derivated from Electrical Resistivity Tomography (ERT), and inverted surface micro-gravity data. The correlograms show a well defined pulse for those pairs of receivers whose backazimut is perpendicular to the beltway, which is the main source that generates ambient noise. We show that pulses had a dispersive character due to that define a dispersion curve (fundamental mode of Rayleigh wave) whose velocity values are close to 700 m/s at a frequency of 5 Hz, and tend to average values of 380 m/s in frequencies close to 16 Hz. Then, we build tomography images from the maximum time of the envelope pulse filtering in 18 center frequencies between 4 to 16 Hz. Through the relationship f=Vs/4z we create a 3D model in function of the seudo-depth (z). This model allows to distinguish the irregularity of the subsoil around the mine colapse (5m depth), which underlies a competent structure (Vs>450 m/s) surrounded by vulcano sedimentary material with low Vs values (200 m/s). ERT model show that the low velocity zones are associated with saturation areas, result that is corroborated by low-density values derived from micro-gravity model. The results indicate that the collapse was produced by the hydrostatic imbalance of the competent materials
NASA Astrophysics Data System (ADS)
Khalil, Mohamed A.; Santos, Fernando M.; Farzamian, Mohammad
2014-04-01
Sinai Peninsula occupies a part of the arid zone belt of northern Africa and southwestern Asia. The largest ephemeral stream in the Sinai Peninsula is called Wadi El-Arish, which winds down northward to the Mediterranean Sea. The delta of Wadi El-Arish has been built by the heavy floods of the Wadi. The Quaternary aquifer is the main water supply of the delta of Wadi El-Arish and its vicinities. The combined action of aridity and extensive pumping from the Quaternary aquifer led to a noticeable increase in groundwater salinity. The hydrochemistry and isotope hydrology confirm that the Quaternary aquifer is recharged by an old saline groundwater from the Pre-Quaternary. A hydrogeological connection between Quaternary and Pre-Quaternary aquifers in the form of fault(s) should exist to explain the hydro-tectonic regime of this area. The Bouguer gravity map shows the high gravity anomaly of the doubly plunging anticline of Risan Aniza Mountain to the south of El-Arish area, which is a part of the Syrian Arc System of northern Sinai Peninsula. A 3D density contrast model, 3D Euler deconvolution, horizontal derivative and least square separation have been performed. The findings showed that (1) two deep regional faults extending NE-SW, surround the Risan Aniza anticline, and (2) two deep local N-S faults are in the area of Delta Wadi El-Arish. These deep faults are proposed to bring the deep Cretaceous aquifer into contact with the shallow Quaternary aquifer and work as a hydrogeological connection between both aquifers. The present hypothesis has some geological evidences from the subsurface lithology of the nearby wells.
NASA Astrophysics Data System (ADS)
Pilz, Marco; Parolai, Stefano; Woith, Heiko
2017-01-01