Identifying resistivity-depth information of stratified media by using 1D occam inversion method

2021 ◽  
Author(s):  
S. Ai ◽  
D. Hou ◽  
H. Ni ◽  
Y. Huang ◽  
Y. Ren ◽  
...  
Keyword(s):  
Inversion Method ◽  
Depth Information ◽  
Stratified Media ◽  
Occam Inversion

Inversion of magnetotelluric data for 2D structure with sharp resistivity contrasts

Geophysics ◽  
2004 ◽  
Vol 69 (1) ◽  
pp. 78-86 ◽  
Author(s):  
Catherine de Groot‐Hedlin ◽  
Steven Constable
Keyword(s):  
Real Data ◽  
Fixed Number ◽  
Inversion Method ◽  
Magnetotelluric Data ◽  
2D Structure ◽  
Discrete Values ◽  
Modeling Code ◽  
Occam Inversion ◽  
Synthetic Models ◽  
Good Agreement

We have developed a linearized algorithm to invert noisy 2‐D magnetotelluric data for subsurface conductivity structures represented by smooth boundaries defining sharp resistivity contrasts. We solve for both a fixed number of subsurface resistivities and for the boundary locations between adjacent units. The boundary depths are forced to be discrete values defined by the mesh used in the forward modeling code. The algorithm employs a Lagrange multiplier approach in a manner similar to the widely used Occam method. The main difference is that we penalize variations in the boundary depths, rather than in resistivity contrasts between a large number of adjacent blocks. To reduce instabilities resulting from the breakdown of the linear approximation, we allow an option to penalize contrasts in the resistivities of adjacent units. We compare this boundary inversion method to the smooth Occam inversion for two synthetic models, one that includes a conductive wedge between two resistors and another that includes a resistive wedge between two conductors. The two methods give good agreement for the conductive wedge, but the solutions differ for the more poorly resolved resistive wedge, with the boundary inversion method giving a more geologically realistic result. Application of the boundary inversion method to the resistive Gemini subsalt petroleum prospect in the Gulf of Mexico indicates that the shape of this salt feature is accurately imaged by this method, and that the method remains stable when applied to real data.

A Weighting Function-Based Method for Resistivity Inversion in Subsurface Investigations

2020 ◽  
Vol 25 (1) ◽  
pp. 129-138
Author(s):  
Lichao Nie ◽  
Zhao Ma ◽  
Bin Liu ◽  
Zhenhao Xu ◽  
Wei Zhou ◽  
...  
Keyword(s):  
Objective Function ◽  
Weighting Function ◽  
Real Data ◽  
Weighting Factor ◽  
Inversion Method ◽  
Depth Information ◽  
Detection Accuracy ◽  
Resistivity Inversion ◽  
Inversion Procedure ◽  
Anomalous Bodies

There is a high demand for high detection accuracy and resolution with respect to anomalous bodies due to the increased development of underground spaces. This study focused on the weighted inversion of observed data from individual array type electrical resistivity tomography (ERT), and developed an improved method of applying a data weighing function to the geoelectrical inversion procedure. In this method, the weighting factor as an observed data weighting term was introduced into the objective function. For individual arrays, the sensitivity decreases with increasing electrode interval. Therefore, the Jacobian matrices were computed for the observed data of individual arrays to determine the value of the weighting factor, and the weighting factor was calculated automatically during inversion. In this work, 2D combined inversion of ERT data from four-electrode Alfa-type arrays is examined. The effectiveness of the weighted inversion method was demonstrated using various synthetic and real data examples. The results indicated that the inversion method based on observed data weighted function could improve the contribution of observed data with depth information to the objective function. It has been proven that the combined weighted inversion method could be a feasible tool for improving the accuracies of positioning and resolution while imaging deep anomalous bodies in the subsurface.

scholarly journals The collocation approach to Moho estimate

2014 ◽  
Vol 57 (1) ◽  
Author(s):  
Riccardo Barzaghi ◽  
Ludovico Biagi
Keyword(s):  
Gravity Data ◽  
The Body ◽  
Observation Equation ◽  
Moho Depth ◽  
Inversion Method ◽  
Depth Information ◽  
Constant Density ◽  
Separation Surface ◽  
Collocation Approach ◽  
Moho Depths

<p>In this paper, the collocation approach to Moho estimate is presented. This method is applied to the inversion of gravity data that can be complemented by Moho depth information coming from e.g. seismic information. In this context, a two layers model is considered and discussed in order to give a general theoretical framework for the inversion method. A body with two inner constant density layers and an inner separation surface between is considered and a uniqueness theorem is proved for the estimability of the separation surface given the gravity outside the body itself. Based on this result, a discussion is given on the estimation of the Moho depths based on terrestrial gravity observations. The observation equation is presented and its local planar approximation is derived. The application of the collocation method to the estimate of Moho depths is then studied and discussed in relationship to the planar observation equation. Also, numerical tests are presented. To this aim, the collocation inversion algorithm is implemented and tested on simulated data to prove its effectiveness. The results show that the proposed method is reliable provided that proper data reductions for model discrepancies are taken into account.</p>

Formulation, Design and Development of Niosome Based Topical Gel for Skin Cancer

2017 ◽  
Vol 2 (3) ◽  
Keyword(s):  
Skin Cancer ◽  
Drug Release ◽  
Hemorrhagic Cystitis ◽  
The Body ◽  
Cancer Drug ◽  
Inversion Method ◽  
Body Parts ◽  
Basal Cells ◽  
Formulation Design ◽  
Topical Gel

Melanoma is the most dangerous type of skin cancer in which mostly damaged unpaired DNA starts mutating abnormally and staged an unprecedented proliferation of epithelial skin to form a malignant tumor. In epidemics of skin, pigment-forming melanocytes of basal cells start depleting and form uneven black or brown moles. Melanoma can further spread all over the body parts and could become hard to detect. In USA Melanoma kills an estimated 10,130 people annually. This challenge can be succumbed by using the certain anti-cancer drug. In this study design, cyclophosphamide were used as a model drug. But it has own limitation like mild to moderate use may cause severe cytopenia, hemorrhagic cystitis, neutropenia, alopecia and GI disturbance. This is a promising challenge, which is caused due to the increasing in plasma drug concentration above therapeutic level and due to no rate limiting steps involved in formulation design. In this study, we tried to modify drug release up to threefold and extended the release of drug by preparing and designing niosome based topical gel. In the presence of Dichloromethane, Span60 and cholesterol, the initial niosomes were prepared using vacuum evaporator. The optimum percentage drug entrapment efficacy, zeta potential, particle size was found to be 72.16%, 6.19mV, 1.67µm.Prepared niosomes were further characterized using TEM analyzer. The optimum batch of niosomes was selected and incorporated into topical gel preparation. Cold inversion method and Poloxamer -188 and HPMC as core polymers, were used to prepare cyclophosphamide niosome based topical gel. The formula was designed using Design expert 7.0.0 software and Box-Behnken Design model was selected. Almost all the evaluation parameters were studied and reported. The MTT shows good % cell growth inhibition by prepared niosome based gel against of A375 cell line. The drug release was extended up to 20th hours. Further as per ICH Q1A (R2), guideline 6 month stability studies were performed. The results were satisfactory and indicating a good formulation approach design was achieved for Melanoma treatment.

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