THE INTERPRETATION OF GEOPHYSICAL DATA

Geophysics ◽  
1937 ◽  
Vol 2 (2) ◽  
pp. 95-113 ◽  
Author(s):  
Ludwig W. Blau
Keyword(s):  
Physical Properties ◽  
Geophysical Methods ◽  
Present Knowledge ◽  
Geophysical Data ◽  
Surface Mapping ◽  
Contour Maps ◽  
Physical Effects ◽  
Data Result ◽  
Geologic Information

Geophysical data result from measurements of physical properties. The geophysicist postulates certain possible physical causes of the observed effects. The geologist reasons from observed geologic effects to geologic causes. The difficulties confronting the interpretation of physical effects as reflected in geophysical data in terms of geologic causes are pointed out. The author takes the position that geophysical data must be worked up independently. A competent geophysicist‐geologist may combine geophysical and geologic information in the preparation of a report which will then, and only when this procedure is followed, include all present knowledge of the area under investigation. The requirement that geophysical data be immediately translatable into geologic language and furnish material for drawing geologic contour maps is shown to be incompatible with the nature of geophysical data. Attention is drawn to the changing geophysical scene and to the tendency to use geophysical methods after they have ceased to be adequate for the solution of prospecting problems. It is suggested that geology can aid geophysics principally through library reconnaissance and advance surface mapping. Geophysics has become a serious competitor of geology in the search for oil, and the geophysic‐geological ecotone has advanced steadily into geologic territory.

The use of geophysical prospecting for imaging active faults in the Roer Graben, Belgium

Geophysics ◽  
2001 ◽  
Vol 66 (1) ◽  
pp. 78-89 ◽  
Author(s):  
Donat Demanet ◽  
François Renardy ◽  
Kris Vanneste ◽  
Denis Jongmans ◽  
Thierry Camelbeeck ◽  
...  
Keyword(s):  
High Resolution ◽  
Physical Properties ◽  
Fault Zone ◽  
Geophysical Methods ◽  
Depth Range ◽  
Electrical Tomography ◽  
Reflection Seismic ◽  
Refraction Seismic ◽  
Geophysical Surveys ◽  
Geophysical Techniques

As part of a paleoseismological investigation along the Bree fault scarp (western border of the Roer Graben), various geophysical methods [electrical profiling, electromagnetic (EM) profiling, refraction seismic tests, electrical tomography, ground‐penetrating radar (GPR), and high‐resolution reflection seismic profiles] were used to locate and image an active fault zone in a depth range between a few decimeters to a few tens of meters. These geophysical investigations, in parallel with geomorphological and geological analyses, helped in the decision to locate trench excavations exposing the fault surfaces. The results could then be checked with the observations in four trenches excavated across the scarp. Geophysical methods pointed out anomalies at all sites of the fault position. The contrast of physical properties (electrical resistivity and permittivity, seismic velocity) observed between the two fault blocks is a result of a differences in the lithology of the juxtaposed soil layers and of a change in the water table depth across the fault. Extremely fast techniques like electrical and EM profiling or seismic refraction profiles localized the fault position within an accuracy of a few meters. In a second step, more detailed methods (electrical tomography and GPR) more precisely imaged the fault zone and revealed some structures that were observed in the trenches. Finally, one high‐resolution reflection seismic profile imaged the displacement of the fault at depths as large as 120 m and filled the gap between classical seismic reflection profiles and the shallow geophysical techniques. Like all geophysical surveys, the quality of the data is strongly dependent on the geologic environment and on the contrast of the physical properties between the juxtaposed formations. The combined use of various geophysical techniques is thus recommended for fault mapping, particularly for a preliminary investigation when the geological context is poorly defined.

Geophysical research of the undefined on the surface of the medieval nacropolis Shekshovo-9 (Suzdal Opole)

2020 ◽  
pp. 3-15
Author(s):  
I. N. Modin ◽  
S. A. Erokhin ◽  
A. M. Krasnikova ◽  
I. G. Shorkunov ◽  
V. A. Shevchenko ◽  
...  
Keyword(s):  
Geophysical Methods ◽  
Main Idea ◽  
Geophysical Data ◽  
Geophysical Research ◽  
Soil Structures ◽  
Geophysical Study ◽  
Archaeological Objects

The problem of modern archeology is the study of monuments that are not expressed on the surface due to centuries of plowing. Using the example of a geophysical study of the Shekshovo 9 monument (Suzdal Opolie region), we consider the use of geophysical methods for mapping the structure of the necropolis. The main idea is to search and interpret archaeological objects in geophysical data as heterogeneities towards background geological and soil structures.

scholarly journals Proposed methodology for measurement, survey and assessment of vertical deformation of structures

2016 ◽  
Vol 34 (3) ◽  
pp. 276-296 ◽  
Author(s):  
Jonathan Ruiz-Jaramillo ◽  
Emilio Mascort-Albea ◽  
Antonio Jaramillo-Morilla
Keyword(s):  
Three Dimensional ◽  
Outcome Analysis ◽  
Vertical Deformation ◽  
Surface Mapping ◽  
Content Type ◽  
Contour Maps ◽  
Survey Results ◽  
Increasing Demand ◽  
High Level ◽  
Inspection Techniques

Purpose – Growing awareness of the importance of preserving the built environment has created an increasing demand for experts capable of performing building inspections to ensure a high level of preservation. Technical surveys include a set of procedures and tests that have become essential tools providing the necessary knowledge required for maintenance, preservation and improvement of buildings. The paper aims to discuss these issues. Design/methodology/approach – Within this set of inspection techniques, this paper presents a method developed to produce vertical deformation plans from the levelling data obtained from different floors of a building. It also explains how to perform accurate levelling and an outcome analysis to provide displacement maps. Thus, based upon obtained measurements, it is possible to achieve 2D contour maps and three-dimensional (3D) surface mapping by means of specialized software that is typically used for cartographic and territorial analysis. Findings – The developed methodology provides easier analysis of the deformation of buildings and structures. Consequently, the method produces relatively accurate outcomes that are sufficient to make a proper assessment that facilitates the diagnostic and decision-making process. The case studies analysed show the applicability and usefulness of the procedure. Originality/value – This sustainable and non-destructive system is an essential instrument for providing valuable and useful information to the specialist. The 2D/3D graphical data displays enable easier analysis of survey results, also aiding comprehension of these results in the context of liability claims.

Resolution measures for 3D magnetic inversions

Geophysics ◽  
2016 ◽  
Vol 81 (2) ◽  
pp. J1-J9 ◽  
Author(s):  
Mark Pilkington
Keyword(s):  
Physical Properties ◽  
Theoretical Basis ◽  
3D Models ◽  
Magnetic Data ◽  
Limited Attention ◽  
Resolution Measure ◽  
Calculated Model ◽  
Geologic Information

Inversion of magnetic data into 3D models is becoming commonplace. The theoretical basis of the method is well established and has been extended to include constraints based on physical properties and geologic information. Nevertheless, only limited attention is paid to assessing the reliability of computed models, which usually involves deriving some measure of how well features within the models can be resolved. Resolution lengths determined from resolution matrices can be unrealistically small, suggesting that the recovered models are more reliable than they really are. One cause of this effect is the calculated model itself, which directly influences the character of the resolving functions. We have developed an approximate resolution measure not affected by the calculated model, and we found it to give more realistic resolving lengths. This approximation is computationally less demanding and can be calculated prior to inversion. It suggests that the resolution length is equal to the depth of the parameter or model feature of interest.

scholarly journals A new model for quantifying subsurface ice content based on geophysical data sets

2010 ◽  
Vol 4 (2) ◽  
pp. 787-821 ◽  
Author(s):  
C. Hauck ◽  
M. Böttcher ◽  
H. Maurer
Keyword(s):  
Seismic Velocity ◽  
Geophysical Methods ◽  
Geophysical Data ◽  
Swiss Alps ◽  
Unfrozen Water ◽  
Detailed Knowledge ◽  
Data Sets ◽  
Rock Glacier ◽  
Heterogeneous Distribution ◽  
Rock Glaciers

Abstract. Detailed knowledge of the material properties and internal structures of frozen ground is one of the prerequisites in many permafrost studies. In the absence of direct evidence, such as in-situ borehole measurements, geophysical methods are an increasingly interesting option for obtaining subsurface information on various spatial and temporal scales. The indirect nature of geophysical soundings requires a relation between the measured variables (e.g. electrical resistivity, seismic velocity) and the actual subsurface constituents (rock, water, air, ice). In this work we present a model, which provides estimates of the volumetric fractions of these four phases from tomographic electrical and seismic images. The model is tested using geophysical data sets from two rock glaciers in the Swiss Alps, where ground truth information in form of borehole data is available. First results confirm the applicability of the so-called 4-phase model, which allows to quantify the contributions of ice-, water- and air within permafrost areas as well as detecting the firm bedrock. Apart from a similarly thick active layer with enhanced air content for both rock glaciers, the two case studies revealed a heterogeneous distribution of ice and unfrozen water within rock glacier Muragl, where bedrock was detected at depths of 20–25 m, but a comparatively homogeneous ice body with only minor heterogeneities within rock glacier Murtèl.

scholarly journals FEATURES OF THE GEOLOGICAL STRUCTURE OF SEDIMENTARY COVER OF FROLOVSKAYA MEGADEPRESSION DERIVED FROM THE RESULTSOF GENERALIZATION OF GEOLOGICAL AND GEOPHYSICAL DATA

2018 ◽  
pp. 7-16
Author(s):  
S. R. Bembel ◽  
V. G. Kobzov ◽  
R. M. Bembel ◽  
F. Z. Khafizov
Keyword(s):  
Sedimentary Cover ◽  
Geophysical Methods ◽  
Geological Structure ◽  
Geophysical Data ◽  
Seismic Profiles ◽  
Gravity And Magnetic ◽  
Drilling Data ◽  
Entire Complex ◽  
Cretaceous Deposits

The article is devoted to the features of the geological structure of Jurassic-Cretaceous deposits of Frolovskaya megadepression. These features are derived from the results of the generalization of the materials of regional seismic profiles, maps of gravity and magnetic prospecting, drilling data. The main petroleum prospects are associated with Jurassic deposits and pre-Jurassic basement. We conclude that it is necessary to intensify further researches with carrying out the entire complex of geophysical methods, including magnetic and gravity prospecting with an increased density of observations.

scholarly journals Assessment of the facial affiliation of local oil and gas objects based on geophysical data

2021 ◽  
Vol 21 (4) ◽  
pp. 241-247
Author(s):  
Boris A. Golovin ◽  
◽  
Konstantin B. Golovin ◽  
Marina V. Kalinnikova ◽  
Sergey A. Rudnev ◽  
...  
Keyword(s):  
Oil And Gas ◽  
Facies Analysis ◽  
Geophysical Methods ◽  
Well Logging ◽  
Geophysical Data ◽  
Gas Content ◽  
Seismic Exploration ◽  
Core Material ◽  
Genetic Characteristics ◽  
Reservoir Potential

In the established practice of geological exploration for oil and gas conclusions about the facies belonging of the rocks of oil and gas basins and individual exploration areas were made mainly on the basis of the study of core material. Recently for this purpose the results of seismic exploration and well logging have been used. Geophysical methods despite their obvious progress are indirect and intermittent core sampling and incomplete coring make facies analysis difficult. Тhe study of cuttings during the well logging process makes it possible to fill this gap through direct continuous observations along the well section. The use of the whole complex of geophysical methods allows one to mutually compensate for the limitations and disadvantages of each of them and more fully and reliably assess the genetic characteristics and reservoir potential of productive deposits. Sequential accumulation, comparison and analysis of heterogeneous geophysical data make it possible to continuously refine apriori facies models and forecast oil and gas content which ultimately allows to optimize the directions and volumes of drilling.

Multiphysics anomaly map: A new data fusion workflow for geophysical interpretation

2020 ◽  
Vol 8 (2) ◽  
pp. B35-B43
Author(s):  
Julio Cesar S. O. Lyrio ◽  
Paulo T. L. Menezes ◽  
Jorlivan L. Correa ◽  
Adriano R. Viana
Keyword(s):  
Data Fusion ◽  
Geophysical Methods ◽  
Real Data ◽  
Logistic Function ◽  
Geophysical Data ◽  
Data Set ◽  
Geophysical Interpretation ◽  
Wide Range ◽  
Anomaly Map ◽  
Different Response

When collecting and processing geophysical data for exploration, the same geologic feature can generate a different response for each rock property being targeted. Typically, the units of these responses may differ by several orders of magnitude; therefore, the combination of geophysical data in integrated interpretation is not a straightforward process and cannot be performed by visual inspection only. The multiphysics anomaly map (MAM) that we have developed is a data fusion solution that consists of a spatial representation of the correlation between anomalies detected with different geophysical methods. In the MAM, we mathematically process geophysical data such as seismic attributes, gravity, magnetic, and resistivity before combining them in a single map. In each data set, anomalous regions of interest, which are problem-dependent, are selected by the interpreter. Selected anomalies are highlighted through the use of a logistic function, which is specially designed to clip large magnitudes and rescale the range of values, increasing the discrimination of anomalies. The resulting anomalies, named logistic anomalies, represent regions of large probabilities of target occurrence. This new solution highlights areas where individual interpretations of different geophysical methods correlate, increasing the confidence in the interpretation. We determine the effectiveness of our MAM with application to real data from onshore and offshore Brazil. In the onshore Recôncavo Basin, the MAM allows the interpreter to identify a channel where a drilled well found the largest sandstone thickness on the area. In a second example, from offshore Sergipe-Alagoas Basin, the MAM helps differentiate between a dry and an oil-bearing channel previously outlined in seismic data. Therefore, these outcomes indicate that the MAM is a valid interpretation tool that we believe can be applied to a wide range of geologic problems.

OIL AND GAS EXPLORATION IN ALABAMA, GEORGIA, AND FLORIDA

Geophysics ◽  
1953 ◽  
Vol 18 (2) ◽  
pp. 340-359 ◽  
Author(s):  
Robert B. Baum
Keyword(s):  
Cross Sections ◽  
Oil And Gas ◽  
Geophysical Methods ◽  
Oil Field ◽  
Oil Fields ◽  
Seismic Events ◽  
Oil And Gas Exploration ◽  
Contour Maps ◽  
Reflection Seismic ◽  
Southern Florida

The discovery of the Pollard oil field in southern Alabama early in 1952 sparked a campaign of leasing and exploration which spread quickly into Georgia and Florida. Three fields in southwestern Alabama and one in southern Florida account for all the oil production in the three states. Some aspects of the general geology and geophysics of the area, illustrated with maps, cross sections, and correlation charts, suggest the presence of geologic conditions favorable for the possible trapping and accumulation of oil and gas. Early seismograph exploration in much of the area was not effective, but in recent months the tempo of seismic activity has been accelerating, and improvements in instrumental and interpretive techniques are being achieved through current experimental work. The use of the various geophysical methods contributed to the discovery of the four oil fields located in the area. The structural traps indicated by the contour maps of the four fields are of the type sought by the reflection seismic method. Examples of representative reflection records indicate the presence of usable and correlatable seismic events. A seismic cross section prepared from data of this type shows the fault zone associated with the Pollard field. The existence of favorable geologic conditions in the southeastern states and the recent oil field successes at Pollard and South Carlton indicate the continuing of active development and exploration throughout the area.

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