Linear Discontinuities Research Articles

Cohesive Gel (Gummy Bear) Silicone Breast Implant Fracture: Linear Discontinuities and Clefts on MRI.

Cohesive Gel (Gummy Bear) Silicone Breast Implant Fracture: Linear Discontinuities and Clefts on MRI.

A method for analyzing discontinuities characterization using the integration of underground drift point cloud with 3DEC software

The geometric statistical characteristics of rock mass discontinuities, such as mean trace length and intensity, cannot be measured directly and require the use of statistical tools (such as sampling lines, sampling windows, and drilling) for analysis. In this paper, we propose a method for extracting discontinuity characteristics using the 3DEC software in three-dimensional (3D) drift models (3DM). Specifically, we introduce the Surface Disk Discontinuity Model (SDDM) as a representation model for planar and linear discontinuities identified in point clouds. By importing the 3DM and SDDM into 3DEC and utilizing a multi-circular window, we calculate the mean trace lengths and two-dimensional (2D) intensity (P21). Additionally, we propose a method to estimate the three-dimensional (3D) intensity (P32), which provides a more comprehensive reflection of the discontinuous characteristics in different spatial orientations. To validate the proposed method, we apply it to the underground drift of the Jiapigou gold mine in Jilin Province to extract the geometric statistical characteristics of discontinuities. The results demonstrate that our method successfully captures the orientation, trace length, and P32 characteristics of four dominant discontinuity groups in the study area. This approach proves to be an effective technique for utilizing 3D laser scanning to obtain accurate discontinuity characteristics of rock mass.

Multi-CrackNet: A Fast Segmentation and Quantification Combined Method for Rock Discontinuity Traces by Capturing an Image

Discontinuity investigation and characterization onsite is a labor-dependent work because current techniques cannot precisely handle multiple discontinuity identifications automatically under different work conditions. This paper proposes the multi-CrackNet which enables us to identify and segment linear discontinuities (joints and cracks) for random types of rock surface. A modified feature extraction network called the multiscale feature fusion pyramid network (MFFPN) has been developed based on FPN to capture and fuse more sensitive texture features of cracks across different types of background. With the help of a new training scheme by setting up 3 stages of training to simulate the human-based learning process, the established model can learn more features steadily and robustly from well-labelled databases. Additionally, a hybrid pixel-level quantification method is proposed to automatically compute the length, width, and inclination of cracks. Results show that the proposed method can achieve a detection accuracy of 87.1% for 1 to 9 sets of cracks on the rock surface across different types of rock. Case studies in Anshan West are provided to verify the reliability and accuracy of our method in macrolinear discontinuity identification and quantification, which sees great potentials in site investigation by saving a large amount of labor force.

Reproducibility of assessment of full-dilatation Cesarean section scar in women undergoing second-trimester screening for preterm birth.

ABSTRACTObjectiveTo assess the reproducibility of a standardized method of measuring the Cesarean section (CS) scar, CS scar niche and their position relative to the internal os of the uterine cervix by transvaginal ultrasound in pregnant women with a previous full‐dilatation CS.MethodsThis was a prospective, single‐center reproducibility study on women with a singleton pregnancy and a previous full‐dilatation CS who underwent transvaginal ultrasound assessment of cervical length and CS scar characteristics at 14–24 weeks' gestation. The CS scar was identified as a hypoechogenic linear discontinuity of the myometrium at the anterior wall of the lower uterine segment or cervix. The CS scar niche was identified as an indentation at the site of the scar with a depth of at least 2 mm. The CS scar position was evaluated by measuring the distance to the internal cervical os. CS scar niche parameters, including its length, depth, width, and residual and adjacent myometrial thickness, were assessed in the sagittal and transverse planes. Qualitative reproducibility was assessed by agreement regarding visibility of the CS scar and niche. Quantitative reproducibility of CS scar measurements was assessed using three sets of images: (1) real‐time two‐dimensional (2D) images (real‐time acquisition and caliper placement on 2D images by two operators), (2) offline 2D still images (offline caliper placement by two operators on stored 2D images acquired by one operator) and (3) three‐dimensional (3D) volume images (volume manipulation and caliper placement on 2D images extracted by two operators). Agreement on CS scar visibility and the presence of a niche was analyzed using kappa coefficients. Intraobserver and interobserver reproducibility of quantitative measurements was assessed using Bland–Altman plots.ResultsTo achieve the desired statistical power, 72 women were recruited. The CS scar was visualized in > 80% of images. Interobserver agreement for scar visualization and presence of a niche in real‐time 2D images was excellent (kappa coefficients of 0.84 and 0.85, respectively). Overall, reproducibility was higher for real‐time 2D and offline 2D still images than for 3D volume images. The 95% limits of agreement (LOA) for intraobserver reproducibility were between ± 1.1 and ± 3.6 mm for all sets of images; the 95% LOA for interobserver reproducibility were between ± 2.0 and ± 6.3 mm. Measurement of the distance from the CS scar to the internal cervical os was the most reproducible 2D measurement (intraobserver and interobserver 95% LOA within ± 1.6 and ± 2.7 mm, respectively). Overall, niche measurements were the least reproducible measurements (intraobserver 95% LOA between ± 1.6 and ± 3.6 mm; interobserver 95% LOA between ± 3.1 and ± 6.3 mm). There was no consistent difference between measurements obtained by reacquisition of 2D images (planes obtained twice and caliper placed), caliper placement on 2D stored images or volume manipulation (planes obtained twice and caliper placed).ConclusionsThe CS scar position and scar niche in pregnant women with a previous full‐dilatation CS can be assessed in the second trimester of a subsequent pregnancy using either 2D or 3D volume ultrasound imaging with a high level of reproducibility. Overall, the most reproducible CS scar parameter is the distance from the CS scar to the internal cervical os. The method proposed in this study should enable clinicians to assess the CS scar reliably and may help predict pregnancy outcome. © 2022 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Geophysical investigation of crustal structural framework of Ilesha, southwestern Nigeria

The interpretation of the aeromagnetic dataset of Ilesha southwestern Nigeria has been carried out to reveal possible future earthquake hazard as well as establish the groundwater potential of the area. The edge detection methods involving the analytical signal amplitude, the total horizontal derivative, the first vertical derivative and the 3D Euler deconvolution were performed on the residual magnetic intensity anomalies to identify the linear structural discontinuities associated with lithological boundaries/ faults in the area. The upward continuation filter and depth estimation procedures of source parameter imaging and radially averaged power spectrum were applied to the residual magnetic intensity data to map geological structures such as faults as well as determine the depth to crystalline basement rocks in the area. The obtained lineaments observed to trend predominantly towards the NE-SW direction indicative of Pan African Orogeny, suggest possible high yield groundwater aquifer zones. The upward continuation filtered maps showed evidence of deep-lying faults to depth beyond 2 km. The 3D Euler deconvolution plots and spectral analysis revealed depth to magnetic sources ranging from 55 m to 345 m and 13 m to 250 m, respectively. The delineated structural discontinuities in the study area revealed stress history similar to Ifewara-Zungeru fault network, suggestive of possible future earthquake occurrence in the area. It is however recommended that further geophysical studies should involve electrical method to establish the groundwater potential as well as the stability of the basement underlying the area.

Semi-analytical model of multiple fractured horizontal well across a discontinuity in a linear composite reservoir

Abstract Many geologic settings can be treated as linear composite (LC) reservoirs, where linear discontinuities divide the formation into multiple zones with different properties. Although there have been many studies on pressure behavior of production wells in an LC reservoir, most of the studies focus on vertical wells. The modeling of multiple fractured horizontal (MFH) wells in an LC reservoir remains limited. The goal of the present work is to propose a general semi-analytical model of an MFH well situated anywhere in a two-zone LC reservoir. This model can take into account the situation where the horizontal well intersects with the discontinuity and hydraulic fractures are distributed in both the two zones. According to the point-source function method, the semi-analytical solution for an MFH well in LC reservoirs is derived by using superposition principle, fracture discrete scheme and numerical inversion algorithm of Laplace transformation. Type curves of MFH wells far away from a discontinuity and across a discontinuity in an LC reservoir are drawn and analysed, respectively. Furthermore, the effects of some parameters on pressure behavior and rate response of an MFH well across a discontinuity are studied. This research finds that the pressure behavior and rate response of an MFH well across a discontinuity are significantly affected by the well location, properties of hydraulic fractures and formation properties.

Machine‐Learning Characterization of Tectonic, Hydrological and Anthropogenic Sources of Active Ground Deformation in California

AbstractTectonic, hydrological and industrial processes coexist in the dynamic natural environments. However, our knowledge of ground deformation associated with tectonic, hydrological and anthropogenic processes and their interactions remains limited. California represents a natural laboratory that hosts the San Andreas fault system, Central Valley and other aquifer systems, and extensive human extraction of natural resources. The attendant multi‐scale ground deformation that has been mapped using Copernicus Sentinel‐1 Synthetic Aperture Radar (SAR)‐satellite constellation from four ascending and five descending tracks during 2015–2019. We consider the secular horizontal surface velocities and strain rates, constrained from GNSS measurements and tectonic models, as proxies for tectonic processes, and seasonal displacement amplitudes from interferometric SAR (InSAR) time series as proxies for hydrological processes. We synergize 23 types of multidisciplinary datasets, including ground deformation, sedimentary basins, precipitation, soil moisture, topography, and hydrocarbon production fields, using a machine learning algorithm–random forest, and we succeed in predicting 86%–95% of the representative data sets. High strain rates along the SAF system mainly occur in areas with a low‐to‐moderate vegetation fraction (∼0.3), suggesting a correlation of rough/high‐relief coastal range morphology and topography with the active faulting, seasonal and orographic rainfall, and vegetation growth. Linear discontinuities in the long‐term, seasonal amplitude and phase of the surface displacement fields coincide with some fault strands, the boundary zone between the sediment‐fill Central Valley and bedrock‐dominated Sierra Nevada, and the margins of the inelastically deforming aquifer in the San Joaquin Valley, suggesting groundwater flow interruptions, contrasting elastic properties, and heterogeneous hydrological units.

Lateral fluid propagation and strike slip fault reactivation related to hydraulic fracturing and induced seismicity in the Duvernay Formation, Fox Creek area, Alberta

SUMMARY Fault shear slip potential is analysed in the area where induced earthquakes (up to 3.9 Mw) occurred in May–June 2015 approximately 30 km south of Fox Creek, Western Canada Sedimentary Basin, Canada. The induced earthquakes were generated by the hydraulic fracturing of the Upper Devonian Duvernay Formation. Interpretation of a 3-D seismic survey and analysis of the ant tracking attribute identifies a linear discontinuity that likely represents a subvertical fault with strike length of 1.4 km, which is aligned with the zone of induced earthquake hypocentres. 1-D–3-D geomechanical modelling is conducted to characterize mechanical rock properties, initial reservoir pressure and stress field. Hydraulic fracture propagation and reservoir pressure buildup simulations are run to analyse lateral fluid pressure diffusion during well treatment. The interaction of natural fractures introduced as Discrete Fracture Network and hydraulic fractures is tested. 3-D poroelastic reservoir geomechanical modelling is completed to simulate slip reactivation of the identified fault zone. The obtained results support that additional pressure buildup of 20 MPa in treatment wells can propagate laterally along hydraulic fractures (and potentially natural fracture network) for about 550 m and reach the fault zone. The increase of fluid pressure by 20 MPa in the fault zone results in dextral slip along the fault, mostly in the interval of the Duvernay and overlying Ireton Formations, corroborating prior focal mechanism results and hypocentral depths. The simulations indicate that lateral transmission of additional fluid pressure from the fracturing stimulation area to the fault zone could happen in a few days after the treatment of lateral wells that is supported by the observed induced earthquakes. This study helps to quantify changes in fluid pressure and stresses that may result in fault shear slip during hydraulic fracturing and predict the potential of induced seismicity connected to hydrocarbon production from the Duvernay Play.

Exploring the Interactions Between Rift Propagation and Inherited Crustal Fabrics Through Experimental Modeling

AbstractContinental rifting is a geodynamic process that involves the breakup of the crust and may eventually evolve to seafloor spreading. Although it is often assumed to be a product of orthogonal divergence, continental rifting may result from oblique extension, and in several cases, it is related to the rotation of plates or crustal blocks about a vertical axis. This implies the occurrence of rifts with straight but not parallel margins and rift axis‐parallel gradients in extension velocity and amount of strain. The effects of rift propagation through the continental crust has only recently started to be addressed, and even less investigated is the interaction between rift propagation and inherited crustal fabrics. We have studied this issue by carrying out a series of analog laboratory experiments. Modeling results suggest that inherited linear discontinuities in the model brittle upper crust that are oriented above a threshold angle (≥45°) from the orthogonal to the rift axis have the ability to interact with rift‐related structures. Depending on their orientation, such inherited discontinuities are reactivated as either transfer zones or rift‐bounding faults. We compare our models with four natural prototypes in which rift propagation is likely to have occurred (the Trans Mexican Volcanic belt, the Gofa Province, the Gulf of Suez, and the Kenya Rift). For each case study, we show how the kinematics of propagating rifts is comparable to our model results, and we provide insights into how rift‐related deformation may interact with inherited crustal fabrics.

Application of seismic prospecting to determine the width of influence of surface faults associated to land subsidence – a case of study in the Aguascalientes Valley, México

Abstract. Aguascalientes valley, located in the central part of México, is affected for a land subsidence process triggered by groundwater withdrawal since the 1980's. Currently, the occurrence and the reactivation of surface faults and earth fissures due to differential subsidence, is the main concern for government bureaus dealing with urban planning, because of the damages that these terrain discontinuities are able to cause in constructions and infrastructure. The deformation and rupture process produces an active linear discontinuity with a variable width of influence, where the constructions and infrastructure are prone to get damage. Therefore, the determination of this width of influence is critical for urban planning and hazard determination. In this work, the results of a geophysical seismic survey carried out in six surface discontinuities located in the subsidence area of the Aguascalientes Valley, are presented and discussed. The study included acquisition of seismic tomography profiles measured perpendicularly to the discontinuities, in order to obtain the P-wave velocity sections. The resulted P-wave velocity models show a low-velocity anomaly within the fracture trace with widths from 50 to 100 m. This anomaly is interpreted as a mechanically disturbed zone due to the activity of the surface fault, this is, due to the presence of fracturing caused to the adjacent material by the differential subsidence. The results suggest that the material in the disturbed zone, is experiencing a increase in secondary porosity, caused by the deformation and rupture process, and the subsequent generation of small fissures and voids. The results of this study have practical implications because the methodology allows defining the influence zone of an active discontinuity, and therefore, to establish a restricted width along the surface discontinuity. The definition of this restraint zone is a first step to produce a subsidence hazard zoning including not only the discontinuity trace but its width of influence.

Extraction and statistics of discontinuity orientation and trace length from typical fractured rock mass: A case study of the Xinchang underground research laboratory site, China

The geological parameters of rock discontinuities are of great significance for the evaluation of high-level radioactive waste repository and underground research laboratory (URL) site characteristics. To provide sufficient basis for the construction of the Xinchang URL site, this paper presents a comprehensive set of methods for acquisition of discontinuity parameters. In this set of methods, a high precision three-dimensional point cloud model of an outcrop with real geographic information is established based on close-range photogrammetry technology, from which not only planar discontinuities but also linear discontinuities can be identified and extracted by a semi-automatic method. A new fast-fuzzy clustering method is proposed to cluster discontinuity sets. The statistics method based on topographic window projection is improved to increase the rationality of estimating the geometric characteristics of fracture traces. As a preliminary validation, the results of this case study reveal that these methods have good applicability in acquiring discontinuity parameters, which is also conducive to the establishment of a deterministic-stochastic discrete fracture network (DSDFN) model to further analyze the properties of fractured rock mass. In addition, it is preliminarily found that some outcrops different locations have structures with similar geological features to a certain extent; moreover, the fractures exposed on the outcrop surface have distribution characteristics similar to those in the granite body obtained by drilling. Above all, the presented multidisciplinary methods could provide an alternative and practical approach for low-cost and accurate acquisition of discontinuity parameters, and thus, to study the properties of fractured rock mass effectively.

Determination of statistical discontinuity persistence for a rock mass characterized by non-persistent fractures

The discontinuity persistence is an important parameter that affects the strength of rock masses and stability in rock engineering. However, determining the 3D discontinuity persistence in practical field projects remains difficult. This study proposes an approach to determine the 3D discontinuity persistence (percentage of total discontinuity area to the area of the potential failure surface) on the basis of Dijkstra's shortest-path algorithm and Bayesian bootstrap method. First, Dijkstra's shortest-path algorithm is used to determine the linear discontinuity persistence (percentage of total discontinuity trace length to the length of 2D potential failure surface), which is essential to determining 3D discontinuity persistence. Second, geological analysis is performed to deduce 3D discontinuity persistence as a function related to two linear discontinuity persistence in two vertical directions. Lastly, Bayesian bootstrap method is used to analyze the linear and 3D discontinuity persistence. This approach can substantially simplify the process of determining discontinuity persistence and comprehensively considers the uncertainty of the fracture network. The mean, standard deviation, and p-value (i.e., value at the 95% confidence limit) are used as the statistical parameters of the linear and 3D discontinuity persistence.

5D geostatistics for directional variables: Application in geotechnics to the simulation of the linear discontinuity frequency

In geotechnics and geomechanics, many rock mass properties are quantified by numerical variables defined by the observation or the testing of a borehole core sample. The value measured depends not only on the in-situ geographic coordinates of the sample, but also on the in-situ borehole direction. Interpolating such numerical variables in space without accounting for their directionality may produce misleading results, insofar as the interpolated values are representative of the rock mass properties in the sampling directions and not necessarily in other directions. A solution to this issue is to regionalize the geotechnical variables in a five-dimensional space, consisting of the Cartesian product of the three-dimensional Euclidean space and the unit 2-sphere, in order to account for both their geographic and directional variations. Spatial correlation analysis can be performed easily under an assumption of stationarity in the three-dimensional Euclidean space and isotropy on the sphere, so that the covariance or the variogram between two data only depends on their geographic and angular separations. The fitting of nested separable covariance functions eases the search for a valid spatial correlation model and for algorithms to simulate the geotechnical variables in the above-defined five-dimensional space. The concepts are applied to the modeling of the linear frequency of weak veins in a Chilean porphyry copper deposit, where the importance of accounting for directionality is demonstrated. Regionalized azimuthal projections are introduced as a visualization tool for structural geologists and geotechnicians to map the directional variations of the weak vein frequency at given locations in the geographic space.

The Bunce Fault and Strain Partitioning in the Northern Lesser Antilles

AbstractStrain partitioning related to oblique plate convergence has long been debated in Northern Lesser Antilles. Geophysical data acquired during the ANTITHESIS cruises highlight that the sinistral strike‐slip Bunce Fault develops along the vertical, long, and linear discontinuity between the sedimentary wedge and a more rigid backstop. The narrowness of the 20‐ to 30‐km‐wide accretionary wedge and its continuity over ~850 km is remarkable. The Bunce Fault extends as far south as 18.5°N where it anastomoses within the accretionary prism where the sharp increase in convergence obliquity possibly acts as a mechanical threshold. Surface traces related to subducting seamounts suggest that 80% of the lateral component of the convergent motion is taken up by internal deformation within the accretionary prism and by the Bunce Fault. The absence of crustal‐scale, long‐term tectonic system south of the Anegada Passage casts doubt upon the degree of strain partitioning in the Northern Lesser Antilles.

Influence of small intestine wall changes after electrically welded anastomoses of different types for the anastomotic tensile strength

The aim — to study the effect on the clinical rupture properties of the electric welded anastomosis, the morphological transformations in the wall of the small intestine after the linear and multi­point methods application.Materials and methods. In the areas of the small intestine with a diameter of 25 to 26 cm, under the conditions of a complex acute experiment on pigs, two double­row staple anastomoses with a stapler and 72 electro welded spot welds (toothed tweezers with a tip pressure of 1.8 N/mm2) and linear circular (2.1 N/mm2) as an end­to­end type. The program of the electric welding machine «Patonmed» EKVZ­300 (440 kHz) was used. Anastomoses were tested with a slow (up to 15 mm Hg/min) injection of liquid. A blind option was chosen for each type of electro welded connection: before the rupture or to the level of loss of tightness by the bracket anastomosis (24.5 mm Hg). Unbroken anastomoses were sent for histological examination.Results and discussion. All electrically welded anastomoses remained sealed at a bursting pressure of 24.5 mm Hg. A linear discontinuity was observed at 56.6 ± 9.2 mm Hg, point — at 38.2 ± 4.2 mm Hg. The thickness of the linear anastomosis compound was 0.1 to 0.16 mm and was slightly different in morphological characteristics in the segment from 1/2 to 1/3 of the circumference, in which a greater proportion of brakes and the number of gaps between connected coagulated muscle membranes was found, although in general, the integrity of the coagulation changes along the circumference persisted. The break occurred in this segment. The thickness of the point anastomosis fluctuated wavy from 0.8 to 3.4 mm. At the point of reduction of the jagged electrodes, there was a connection of the muscular membranes, a spatial orientation of the cell fragments and fibers, and the formation of a conglomerate. Perifocal muscular layers did not merge, although they were part of the coagulation conglomerate, which covered mainly the muscular and submucosa layers. Serous membranes were connected. On the example of a multipoint electrically welded junction of the intestinal walls, it is possible to estimate the margin of safety, which can have a continuous electro welded connection, and also characterize the permissible unevenness of the morphological transformations while providing clinically necessary strength and tightness parameters.Conclusions. Despite the fluctuations of the electrically welded tissues transformations depth along the ileum anastomosis circumference, the coagulated muscle layers merge presence and the integrity of the welding changes along the anastomosis line, which is based on parameters of the instrument and impulses, provides the significantly higher bursting pressure, comparing the stapled anastomosis. The tissues transformations depth as well as continuous merge density of coagulated muscles and fibers inside the linear type of welded anastomosis establishes it’s comparatively exceeded strength.

Near-diffraction-limited focusing with gradient high-impedance metasurface

We propose a new technique for wavefront manipulation using a high-impedance metasurface made of a reflectarray containing gradient mushroom-shaped elements, which provide a full-range phase shift for accomplishing the manipulation. The reflection phase of the high-impedance metasurface shows a linear discontinuity dependence on the sizes of the unit elements. Near-diffraction-limited focusing and a high efficiency of 80% were achieved by modulating the reflection phase using the gradient high-impedance metasurface. The experimental results and the theoretical simulation were in good agreement. The proposed gradient high-impedance metasurface can be employed for highly effective wavefront engineering.

Small-displacement linear surface ruptures of the 2016 Kumamoto earthquake sequence detected by ALOS-2 SAR interferometry

We constructed and analyzed the ground surface displacement associated with the 2016 Kumamoto earthquake sequence using satellite radar interferometry images of the Advanced Land Observing Satellite 2. The radar interferogram generally shows elastic deformation caused by the main earthquakes, but many other linear discontinuities showing displacement are also found. Approximately 230 lineaments are identified, some of which coincide with the positions of known active faults, such as the main earthquake faults belonging to the Futagawa and Hinagu fault zones and other minor faults; however, there are much fewer known active faults than lineaments. In each area, the lineaments have a similar direction and displacement to each other; therefore, they can be divided into several groups based on location and major features. Since the direction of the lineaments coincides with that of known active faults or their conjugate faults, the cause of the lineaments must be related to the tectonic stress field of this region. The lineaments are classified into the following two categories: (1) main earthquake faults and their branched subfaults and (2) secondary faults that are not directly related to the main earthquake but whose slip was probably triggered by the main earthquake or aftershocks.

Application of a Multi-dimensional Limiting Process to Central-Upwind Schemes for Solving Hyperbolic Systems of Conservation Laws

In this paper, we study semi-discrete central-upwind difference schemes with a modified multi-dimensional limiting process (MLP) to solve two-dimensional hyperbolic systems of conservation laws. In general, high-order central difference schemes for conservation laws involve no Riemann solvers or characteristic decompositions but have a tendency to smear linear discontinuities. To overcome this drawback of central-upwind schemes, we use a MLP that uses multi-dimensional information for slope limitation to control the oscillations across discontinuities for multi-dimensional applications. Some numerical results are provided to demonstrate the performance of the proposed scheme.

Second Order Finite Volume Scheme on Tetrahedral Meshes for Three-Dimensional Maxwell’s Equations with Discontinuous Dielectric Permittivity

An extension of a finite volume scheme for three-dimensional Maxwell’s equations with discontinuous dielectric permittivity on tetrahedral meshes is discussed. The scheme is second order accurate in time and space for regions with linear and curvilinear discontinuities. It was tested on problems with linear and curvilinear discontinuity configurations. The test results support the second order accuracy of the proposed scheme.

High Spatial and Spectral Details Retention Fusion and Evaluation

To retain spatial and spectral details simultaneously from source images is a trade-off in image sharpening. Fourier and wavelet transform based image fusion methods retain better spectral quality but represent less spatial details as in source images. Wavelets and Laplacian pyramid perform well only at linear discontinuities because they do not consider the geometric properties of structures and do not exploit the regularity of edges. In this paper we proposed a novel image fusion method to preserve high spatial and spectral details based on the curvelet transforms. Curvelet transforms overcome the difficulty to identify the critical transient features. To retain high spatial details, finer and detailed scale coefficients of High Resolution (HR) PAN image are substituted in Low Resolution (LR) multispectral (MS) bands in the Fast Discrete Curvelet Transforms (FDCT) domain. Spectral details in the fused image are preserved by following the shape of the spectral reflectance curve of each pixel in the resample MS image. Spectral profile of the each pixel in spatially fused image is parallel to the spectral profile of the corresponding pixel in the resampled MS image. For experimental study of this method, Indian Remote Sensing (IRS) Resourcesat-1 LISS IV images are used as LR MS image and Cartosat-1 images are used as HR PAN Image. Proposed fusion method is evaluated against state of the art fusion techniques and quality measures.