THE XVIth SYMPOSIUM OF EARTH PHYSICS AND APPLIED GEOPHYSICS

Within the XVIth Symposium 67 papers were programmed; besides 4 lectures in the opening meeting.
The papers were presented within three traditional sections:
– Section I – Geophysical researches for energy resources and engineering
geophysics – 7 papers
– Section II – Geophysical investigations for solid mineral substances – 27 papers
– Section III – Earth Physics – 29 papers.

OPENING MEETING

PROBLEMS OF THE GEOPHYSICAL ACTUALITY
Liviu Constantinescu
Romanian Academy, Bucharest

An important actual problems of geophysics – with the two fold meaning of the word "actual": (1) of present-day relevance and (2) of obvious effectiveness – various aspects of the interdisciplinarity in geophysical research are mentioned not only in the conventional integrated interpretation of results, but also in the initial phases planning, data acquisition and processing. With special emphasis are presented the implications of geophysical activity in the programmes being carried out under the aegis of ICSU and/or UNESCO, such as the International Geosphere – Biosphere Programme and the International Decade for Natural Disasters Reduction.
Key words: interdisciplinarity, data acquisition, processing and interpretation, international pogrammes.

RADU BOTEZATU – A REMARKABLE PROSPECTOR
OF THE ROMANIAN TERRITORY
M. Visarion
Institute of Geology and Geophysics, Bucharest

Among the personalities who brilliantly represented the earth sciences in Romania, Radu Botezatu stands out through his valuable efforts in deciphering the deep structure and the development of a new conceptual framework for the geological interpretation of the geophysical data. The researches carried out over the Carpathian Orogene, the Moesian Platform, the East European Platform and the North Dobrogea Intracratonic Orogene provided new information on the structural edifice with implications in the orientation of the geophysical prospecting activity. The metrological and methodological improvements, the processing of the primary geophysical data by adequate means, including original methods, the modelling of the potential fields anomalies are factors that ensured the reduction of the risk in the geological interpretation of the results. The work achieved by Radu Botezatu designates him as one of the most prominent researchers who contributed to the appearance of a new discipline "The geological interpretation of the geological data" within the wider sphere of geosciences.
Key words: intracratonic orogene, modelling of the potential fields anomalies.

GEOPHYSICAL DATA BASE IN ROMANIA; NECESSITY AND POSSIBILITIES
M. Pauca
Bucharest University, Faculty of Geology and Geophysics, Bucharest

The note presents the proposal for creating the data base of the Geophysical Department. It justifies the need for a data base and how the department is involved in creating it. The structure and some of the technical elements are presented together with its means of access. The note ends with an appeal to all the Romanian Geophysicists to support this action.
Key words: Data base, file, viewing, human potential, Geophysical Department.-

THE MULTIDISCIPLINARY CHARACTER OF SOME THEORETICAL RESULTS
OF EXPLORATION GEOPHYSICS
V. Bardan
Prospecting Company, Computer Center, Bucharest

In the last 30 years exploration geophysics and mainly reflexion seismics developed in a very large extent due to the implementation of digital techniques both for field acquisition and data processing. These new techniques allowed a substantial progress in theoretical and applied research for the exploration geophysics, resulting in the new trends for development. New concepts and results from the other branches of science as: statistical communication theory, wave propagation theory, signal processing theory, etc., were used with a practical purpose. Therefore the exploration geophysics research got an interdisciplinary character.
Also, it could be possible that some solution of the problems arisen in exploration geophysics be extended to other fields of physics. In this paper we try to emphasize the multidisciplinary character of these results. For this reason some geophysical results published by the author in well-known international scientific journals or presented abroad at several meetings or symposium are commented upon.
Key words: exploration geophysics, reflexion seismics, theoretical and applied results, interdisciplinary character, multidisciplinary character, fields of physics.

Ist Section: GEOPHYSICAL RESEARCHES FOR ENERGY RESOURCES
AND ENGINEERING GEOPHYSICS

NEW RESULTS OBTAINED FROM WELL LOGS SOURCE ROCKS EVALUATION
AND HYDROCARBON MIGRATION ON THE ROMANIAN TERRITORY
V. Negoita
Institute of Technological Research and Design, Campina

Nowadays, the identification of source rocks, the quantification of organic matter contained by them as well as the thermal evolution stage estimation of this organic matter are carried out by geochemical laboratory analyses on a preselected reduced number of cuttings and samples from the boreholes. However, the same tasks may be approached using the continuous measurements of well logs recorded during the customary wireline operations. Such a method developed in Romania under the name of "Well Logging Prospecting" is particularly devoted to sedimentary basin study.
Several field applications related to source rock evaluation and hydrocarbon primary and secondary migration are finally presented.
Key words: well logs, source rock, hydrocarbon migration.

GEOPHYSICAL SURVEY CARRIED OUT BY FOREIGN COMPANIES IN ROMANIA
M. Visarion
Institute of Geology and Geophysics, Bucharest

The paper presents data on the geophysical surveys carried out in the period 1925 – 1947 by foreign companies (Astra Romana, Romanian-American Companie Générale de Géophysique, Société de Prospection Electrique Schlumberger, A.B.E.M. etc.) with a view to discovering oil structures mostly in the Carpathian Foredeep, Moesian Platform and Pannonian Depression. The researches carried out in the Transylvanian and Pannonian depressions until the year 1916 and in the period 1941 – 1943 in the territories temporarily and arbitrarily annexed to neighboring countries are also taken into account. This paper deals with the geophysical methods employed, the equipment and methodologies adopted pointing out the contributions brought to the outlining of the geological structure related to the present knowledge.

ON DIP-MOVEOUT IMPLEMENTATION
V. Bardan1, Elena Chiscan1, N. Moldoveanu2
1Prospecting Company, Computer Center, Bucharest, Romania
2GECO-SCHLUMBERGER , Calgary, Canada

The main benefits of including dip-moveout (DMO) in seismic data processing are that (1) stacking velocities after DMO are dip-independent, and (2) "reflection point smear" associated with dipping events is eliminated by laterally shifting the reflection points to their zero-offset position. These effects of DMO are also beneficial for estimation of stacking velocities by simplifying the interpretation of velocity analysis. There are many different approaches to accomplish DMO. The DMO methods are implemented and tested. By using examples of synthetic and real seismic sections we demonstrate the feasibility of these DMO methods.
Key words: seismic data processing, dip-moveout (DMO), implementation, test, feasibility.

INVESTIGATION OF THE GEOTHERMAL AREAS IN THE
NEOGENE VOLCANIC ZONE OF THE EAST CARPATHIANS
(GURGHIU – CALIMANI – HARGHITA MOUNTAINS)
Al. Patruti1, Emilia Patruti1, C. Visarion2, C. David1, A. Viforeanu2
1Prospecting Company, Bucharest
2Institute of Geology and Geophysics, Bucharest

This work presents some peculiarities related to application of geothermal, geoelectrical methods in investigating geothermal areas, results of geothermal, geoelectrical and geochemical anomalies on the area of Gheorghieni, Ciuc and Baraolt depressions being pointed out.
Based upon results formerly presented, the hypothesis of a deep fracture system developing along Olt and Mures valleys is put forward, system constituting the major way for conductive and convective heat transfer from deep zones towards surface.
Key words: geothermal prospecting, geothermal area, depressions, deep fracture, geothermal anomaly.

CONTRIBUTIONS TO THE DETERMINATION OF THE GEOTHERMAL FIELD IN THE SOUTHERN AREA OF THE APUSENI MOUNTAINS
Al. Patruti and Emilia Patruti
Prospecting Company, Bucharest

The presence of geothermal springs in the region (Rapolt, Bobalna, Geoagiu) where a normal geothermal gradient is typical, is explained by the existence in the Rapolt metamorphics of a convective system whose ascending branch reaches the surface in the anticline axis zone.
Various dynamics of underground waters is noticed on the two flanks of the Rapolt anticline, as well as the presence of fractured zones constituting circulating ways of thermal waters within the Rapolt metamorphics.
Key words: convective system, normal geothermal gradient, Rapolt metamorphics, anticline.

MICROSEISMIC RESONANCE METHOD FOR DETECTING HOLES UNDER
THE CONCRETE PLATFORMS OF ROADS AND INDUSTRIAL PLANTS
M. Pauca, T. Orban
Bucharest University, Faculty of Geology and Geophysics, Bucharest

The method allows the estimation of the size of places and the holes by measuring the resonance frequency and attenuation factors of the zone of the concrete plate which is not supported by the ground. The measured vibration may be the result of an artificial impact or the vibration of the surrounding plant. This method is recommended for the control of heavy traffic roads, airfield runways, technological platforms in order to avoid serious accidents due to ruptures over such holes.
The paper presents several geophysical non-destructive methods for detecting holes, the used technologies and results interpretation, emphasizing the advantages of microseismic resonance method.
Key words: resonance frequency, geophysical non-destructive methods.

SPECIAL SEISMIC SURVEYS ON THE SALT DOMES
V. Manj, P. Cristea
Institute of Geology and Geophysics, Bucharest

The seismic method used to investigate for special purposes the salt domes can offer needful information, as well as the details of complicated structural areas and on in situ geoelastic properties.
Adopting particular techniques of data acquisition and processing we have performed surveys for salt deposits and the main results are put together in this paper.
These results regard directly the detailed structure of flank dip, emphasizing the underground cavities and other inhomogeneities and allowing the evaluation of Poisson's ratio, Young's modulus, shear and bulk modulus in salt works.
The information have been used directly for the salt exploiting monitoring.
Key words: seismic method, aplanatic curves, tomography, P and S velocities, geoelastic properties.

IInd Section: GEOPHYSICAL INVESTIGATION
FOR SOLID MINERAL SUBSTANCES

SOME CONTRIBUTIONS TO RECOGNITION OF THE MAGNETIC ANOMALY
SOURCES FROM THE MOLDAVIAN PLATFORM (SOUTH IASI)
B. Hanu1, C. Cranganu1, Daniela Zamfir2
1"Al. I. Cuza" University, Faculty of Geology-Geography, Iasi
2Prospecting Company, Bucharest

Five main magnetic anomalies of maximum were distinguished within the Moldavian Platform (south Iasi area). They have different spreadings and are superimposed on a magnetic calm background. The negative values grow towards the Prut river (eastward), leading to the idea of an existence, within this zone, of a non-magnetic basement because the sedimentary cover has thicknesses more reduced than in the SW area.
Different tendencies of anomalous orientation of N – S and NW – SE to, finally,
W – E may be observed. Interpreting these anomalies may distinguish interesting aspects about their deeper sources.
Key words: magnetic anomalies, Moldavian platform, anomalous sources.

QUANTITATIVE INTERPRETATION OF GAMMA RAY LOGS
R. S. Constantinescu
Rare Metals State Company, Bucharest

To optimize the accuracy and resolution of the quantitative uranium determination, by gamma ray logs, especially in complex sequences, some methods were tested based on application of the procedures of digital time series analysis; comparative results are discussed. These experiments lead to the elaboration of a quantitative interpretation procedure, started from J. H. Scott's iterative algorithm. By application of a similar technique to the interpretation of gamma-ray spectrometric logs, was elaborated a method of quantitative interpretation of these logs, with complete elimination of the effects of the variation of stripping coefficients between measuring channels.
Key words: quantitative interpretation, gamma log.

A RANDOM NUMBER ALGORITHM FOR GRAVITY
AND MAGNETIC DATA INVERSION
M. Ivan
Bucharest University, Faculty of Geology and Geophysics, Bucharest

A fast algorithm based on the constrained global optimization of an objective function is described. The procedure is applied to gravity magnetic data inversion by using a theoretical but realistic model. Various models consistent with other geological information are reconstructed from the field measurements. They are analyzed using statistical methods. Different objective functions are discussed in terms of speed and accuracy. The multiple minima problem is investigated by using the Jensen inequality.
Better results are obtained with respect to other similar procedures.
Key words: gravity/magnetic, inversion, random numbers, Jensen inequality, The depth of investigation of the electrical prospecting arrangements.

STATISTICAL MODEL FOR AUTOMATICAL INTERPRETATION FOR DATA
OF PHYSICAL FIELD WITH RADIAL PROPAGATION
G. Patriche
Institute of Geology and Geophysics, Bucharest

This is a processing of the Romanian invention No. 77237 of the same author and it consists in a statistical interpretation for observational data, based on the percentage comparison of the transmitting – receiving rays number between the total of them and those carrying anomaly information on the researched medium unit.
The grouping of the medium elements of which the number of rays, corresponding to both categories of information, coincides then represents the form, the size and the location of perturbing geological non-homogeneity, existing between two or more drillings or mine galleries, as well as between each of them and surface.
This model for statistical – automatical interpretation can be used for all physical fields with radial propagation in fault detection purposes and non geological only – by means of the tomography.
Key words: tomography, statistical interpretation, automatical interpretation, transmitting-receiving rays, radial propagation, fault detection, medium elements.

INTEGRATED MAGNETICS AND BIOGEOPHYSICAL RESEARCHES
IN GEOLOGICAL INVESTIGATIONS
L. Besutiu, A. Nicolescu, D. Svoronos
Institute of Geology and Geophysics, Bucharest

Looking for a new approach, able to diminish the uncertainty of the solution gathered within magnetics interpretation, detailed magnetics were performed along with biogeophysical researches in two test areas, Northern Dobrogea located.
The experiment was sustained by the latest results obtained in Romania within the domain of the quantitative analysis of the biogeophysical determinations.
Usual geometrical parameters of the target sources (depth to the roof, dip angle) were computed and compared for both magnetics and biogeophysical data.
Key words: magnetics, biogeophysics, geology, interpretation.

THE GEOPHYSICAL MODEL SIMULATING THE SUMULEU ERUPTIVE
STRUCTURE (GURGHIU MOUNTAINS) BASED ON THE QUANTITATIVE
INTERPRETATION OF GRAVITY AND AEROMAGNETIC DATA
C. Calota1, D. Ioane1, D. Ion2
1Bucharest University, Faculty of Geology and Geophysics, Bucharest
2Institute of Geology and Geophysics, Bucharest

Taking into account the synthesis of geological, petrophysical and geophysical data (mainly gravity and aeromagnetic data), an interpretative model for the Sumuleu volcanic structure has been prepared.
The model will allow the most probable interpretation hypothesis of the geological structure in the much analyzed case within the framework of the East Carpathians volcanic chain.
Key words: Gravity and aeromagneatic modelling, eruptive structure, East Carpathians.

IMAGE PROCESSING WITH ERDAS SYSTEM FOR GEOLOGIC PURPOSES
Vl. Glancz
Institute of Geology and Geophysics, Bucharest

This paper presents the possibilities of satellite image processing with ERDAS (Earth Resources Data Analysis System) to put into evidence the interesting characteristics of images for geologic aims.
The image processing refers particularly to a new method of image "derivation" using convolution filters.
Several examples from our territory are given.
Key words: remote sensing, satellite images, lineament, image processing, filtering, derivation of the image.

INTERPRETING MAGNETIC ANOMALIES: GEOLOGICAL AND PHYSICAL BOUNDARIES
D. Oncescu
Prospecting Company, Bucharest

Chemical analytical data for titanomagnetites content in rocks permitted to appreciate the Curie temperatures of rocks and, according to Kawai's method, the depth of the formation of plutonic igneous rocks. The initial temperature, speed of cooling and depth of the formation of plutonic igneous rocks become sufficiently useful, to estimate the spatial dimensions of a halo where the magnetic properties of surrounding rocks are changed.
So, the magnetic map for Cerbia Zone, Drocea Mountains, permitted to draw two kinds of boundary: a physical boundary between rocks (basalts) thermal affected and unaffected and a geological boundary between the plutonic igneous rocks (granite) and surrounding rocks (basalts).
Key words: magnetization, physical limits, magnetic anomaly.

DETERMINING THE SPECTRAL SIGNATURES FOR SOME TYPES
OF IGNEOUS ROCKS IN THE VISIBLE AND NEAR INFRARED RANGE
(0.3 – 3.0 m) WITH "IRIS" SPECTRORADIOMETER AND SPECTRAL
REFLECTANCE DATA PROCESSING
Anca Maria Vajdea, V. Vajdea, M. Ghiran
Institute of Geology and Geophysics, Bucharest

Knowing the spectral signature allows to deal with the remote sensing techniques on a new basis with the remote sensing techniques on a new basis, superior to the present state, by selecting, during both the process to data acquisition and data processing, the proper spectrum bands in which the materials of interest show diagnostic features.
The paper presents the curves of spectral reflectance of some types of igneous rocks measured in the laboratory and on the field with IRIS (Infra Red Intelligent Spectroradiometer) and the facilities of data processing with the software available.
Key words: electromagnetic radiation, wavelength, spectral reflectance, spectroradiometer, spectra processing, igneous rocks.

GENERAL VIEW ON THE DISTRIBUTION OF PHYSICAL PROPERTIES OF
IGNEOUS ROCKS FROM CALIMANI – GURGHIU – HARGHITA MOUNTAINS
V. Stoenescu, D. Romanescu, Elena Szabo, Anca Georgescu, D. Alexandrescu
Institute of Geology and Geophysics, Bucharest

A graphic synthesis of magnetic properties and density of the igneous rocks from different zones in Calimani-Gurghiu-Harghita mountains is presented. A graduate decrease of the magnetic susceptibility and density, as well as an increase of the remanent magnetization from the north to the south has been observed.
This paper is the result of the researches carried out in the 1980 – 1990 period.
Key words. magnetic properties, density, Calimani-Gurghiu-Harghita mountains.

A PETROMAGNETIC STUDY CONCERNED WITH AMPHIBOLITES
OF THE MIOARELE FORMATION
Vl. Rosca, T. Nestianu, Anca Georgescu
Institute of Geology and Geophysics, Bucharest

A petromagnetic study concerned with amphibolites included in the Mioarele formation (South Fagaras Mountains) showed a series of peculiarities among which a North-South magnetic susceptibility compartments pattern is pointed out. Statistic revealed a long-normal magnetic susceptibility distribution for gneissic rocks and an altered log-normal one for amphibolites. It has been evinced also the remanent magnetization, overall normal, is polarized around the plumb line.
Where metal sulphurs (Ni, Cu) are present, no evidence of a correlation with magnetic properties might be claimed.
Key words: petromagnetics, amphibolite, Fagaras Mountains.

A PECULIAR CASE OF APPLICATIONS OF THE VAJK METHOD ON
THE BOUGUTER GRAVITY MAPS BUILDING WITH VARIABLE DENSITIES
J. Andrei, R. Crahmaliuc, Anca Crahmaliuc
Institute of Geology and Geophysics, Bucharest

The Bouguer gravity map of the North Dobrogea, calculated for the unique density of 2.65 g/cm, points out some supracompensation effects on the area of the Babadag basin. With a view to eliminating those distortions, a Bouguer gravity map with variable densities has been built, through the Vajk method, for the area of this basin. Because of the particular geological conditions, the authors have used a simplified form of the mentioned method, adapted to a semiautomatic calculation system.
Key words: the Bouguer map, variable densities, the Vajk method, the North Dobrogea.

GEOELECTRICAL SURVEY FOR THE SOIL AGGRESSIVITY DETERMINATION
I. Munteanu, D. I. Rosca
Prospecting Company, Bucharest

Applied methodology for estimating soil aggressivity based upon its electrical resistivity is presented in the work. Soil electrical resistivity along a line designed for setting up a metallic water pipe was determined by carrying out measurements with symmetric electrode array, resistivity and vertical electrical sounding. By apparent data inversion, real resistivity sections were derived along the line. The intersection of the pipe-line drawn up on these sections with the resistivity domains, stated upon soil aggressivity criteria, represents the answer to the problem set.
Key words: soil aggressivity, geoelectrical survey, apparent resistivity, real resistivity.

GEOELECTRICAL IVNESTIGATIONS OF LEAD-ZINC MINERALIZATION
IN BUDA MINE EXTENSION
P. Tambrea
Prospecting Company, Bucharest

The paper synthetically presents the results derived from induced polarization resistivity and self potential investigation carried out both for identifying the extension of lead-zinc mineralization and for clearing up geological uncertainties in Buda area, Fagaras Mountains.
Induced polarization, resistivity and natural polarization anomalies outline the continuity of carbonic levels bearing lead-zinc mineralizations in a zone of very complex morphology ranging between Buda and Podul Giurgiului valleys.
Graphically correlating electrical measurement, geological and mining works results, a structural map was drawn up showing the spatial development of mineralized levels in the area between Buda and Podul Giurgiului valleys.
Key words: Buda mine, Fagaras Mountains, induced polarization, resistivity, self potential lead-zinc mineralization.

A GEOELECTRICAL PROCEDURE OF REVEALING THE INTERVALS
WITH HIGH PERMEABILITY IN WATR-BEARING COMPLEXES
LINKED WITH QUATERNARY DEPOSITS IN NORTH DOBROGEA
D. Rosca
Prospecting Company, Bucharest

The work deals with investigation by vertical electrical sounding of water-bearing complexes ranging within Quaternary deposits in North Dobrogea.
A procedure for making up a nomogram enabling to appraise porosity and lithology of the aquifers upon their electrical resistivity and water resistivity has been worked out. Water-bearing complexes resistivities are derived from 1-D inversion VES diagrams, while water resistivity is measured on samples collected from drillings and wells. It has been ascertained that middle porosity rocks in this region are the most permeable ones.
Key words: vertical electric soundings, DC resistivity, Quaternary deposits, water-bearing deposit, North Dobrogea.

GEOELECTRICAL INVESTIGATION OF A MINERALIZED FAULT
IN BASIC ROCKS
M. Munteanu
Prospecting Company, Bucharest

A case of prospecting by geoelectrical methods a sulphide mineralization located on a fracture affecting basic igneous rocks is presented. Mineralization was initially identified by IP and resistivity measurements in time domain, longitudinal gradient variant, and subsequently was intercepted through a baring. For stating the optimum IP and resistivity variant, profile measurements were carried out in various electrode arrangements. Besides, self potential measurements (SP) were conducted, as well as "in situ" polarizability and resistivity ones.
The most intense IP and resistivity anomalies are resulting from profile measurements and pole-dipole soundings, while the images of apparent geoelectrical parameters beast suggesting the geometry of the anomalous body are those ones derived from symmetric electrode array profiling, Schlumberger V.E.S., longitudinal gradient and pole-dipole profiling.
Key words: induced polarization, resistivity, self potential, mineralized fault, basic rocks, measuring arrays.

GEOELECTRICAL CONTRIBUTIONS TO THE RESEARCH OF THE LODE
MINERALIZATIONS OF ROATA-CAVNIC ZONE GUTAI MOUNTAINS
T. Sileam
Prospecting Company, Bucharest

The paper presents the results of geoelectrical survey, by the induced polarization and resistivity method, carried out in zones near to the Roata-Cavnic polymetallic sulphides deposit.
After short considerations concerning the geological structure of the region and field technique used, the geoelectrical significance of the geoelectrical anomalies is presented comparatively with the results of geological research and mining exploration.
Finally some conclusions are emphasized concerning the possibilities and limitations of the used geoelectrical method for the research of the lode mineralizations.
Key words: Cavnic, induced polarization, resistivity, array, lode mineralization, mining exploration.

METHODOLOGICAL CONTRIBUTIONS TO THE GRAVIMETRIC MAPPING
OF THE SHALLOW-WATER MARINE AND LACUSTRINE ZONES
R. G. Dumitru, C. S. Sava, C. Maran
Institute of Geology and Geophysics, Bucharest

This study gives a solution for covering with bottom gravimetric measurements the shallow-water zone of the Black-Sea off-shore and the lacustrine on-shore in order to join the terrestrial and marine gravimetric maps.
This paper presents the results of the experimental measurements carried out in the Razelm-Sinoe lagunar zone.
Key words: gravimetric mapping, marine and lacustrine shallow-water.

GEOTECTONIC FRAMEWORK STRUCTURAL PARTICULARITIES AND
ECONOMIC PERSPECTIVES OF BEIUS BASIN BY SYNTHESIS OF
GEOLOGICAL AND GEOPHYSICAL DATA
C. Dinu, C. Calota, V. Mocanu, D. Ciulavu
Bucharest University, Faculty of Geology and Geophysics, Bucharest

By corroborating geological and geophysical data, existing and of own observation, the ensemble structure of Beius, Basin was outlined.
Data processing and their interpretation pointed out a series of structural alignments, corresponding to some areas of uplift or subsidence basement, along gravity faults. In this framework, the sedimentary formations have important thick variability and some intrusive bodies appear.
Finally, a model of formation and evolution of the basin was carried out. It explains the basin's structure and the economic perspective of different areas from its extent.
Key words: geotectonic framework, structures, economic perspective, geophysical information (seismic, gravity, magnetic), interpreting level of formation and evolution.

THE INVESTIGATION DEPTH OF THE ELECTRICAL PROSPECTION DEVICES
P. Georgescu, D. Ion
Bucharest University, Faculty of Geology and Geophysics, Bucharest

The depth of investigation has been defined till now only for the prospecting of homogeneous or horizontal layered media. In this paper the authors deal with the case of unlayered media giving their own definition for the depth investigation.
Different variants of this parameter as well as the results of the study performed on the theoretical models of unlayered media are presented.
Several examples show that the depth of investigation depends not only on the medium peculiarities and the type of the prospecting arrangement but on the AB/MN value.
Key words: depth of investigation, electrical prospecting arrangement, alpha center.

" CHANNEL-FILL" TYPE FACIES IDENTIFIED BY WELL LOGS
WITH APPLICATIONS ON LEBADA AND SINOE FIELDS (BLACK SEA SHELF)
A. Negut, C. Dinu, D. Lutac, M. Sisman
Bucharest University, Faculty of Geology and Geophysics, Bucharest

The "channel fill" types facies and its specific features on well logs are analyzed in the paper. Using lithological analysis by volume columns obtained by integrated well logs processing from few wells of Lebada and Sinoe Fields as well as seismic information, the possibility of sand-sandstone "channel fill" deposits presence in the Albian formations is inferred.
Some elements of identified sand (sandstone) bodies development predictions and implications concerning the hydrocarbon exploration orientation are underlined.
Key words: geophysical logs, "channel-fill" type facies.

GAMMA RAY SPECTRAL DATA CONTIBUTIONS TO OUTLINING
THE MINERALIZATION ZONE ASSOCIATED WITH NATURAL RADIOACTIVE
ELEMENTS IN DITRAU AREA
I. Manea, L. Podoleanu, I. Fekete
Institute of Geology and Geophysics, Bucharest

This paper presents the basic principles of gamma ray spectral logging, the opportunity of its applications, especially in the investigations of solid mineral ores.
The measurements were accomplished using original models achieved in the Nuclear Geology Laboratory. These helped us to standard the spectral equipment and the determination of the Th, U and K concentrations of the geological formations crossed by the drilling.
Our results (correlated with the results of order specific methods) in several wells in Ditrau area made this method indispensable.
Key words: stripping factors, model, geological interpretation.

THE UTILITY OF THE CORRELATION ANALYSIS
IN THE INTERPRETATION OF GRAVITY DATA
M. Albaiu, C. Postolache
Prospecting Company, Bucharest

The utility of the correlation analysis is presented in the case of gravity data interpretation as a quantification of the possibility to identify anomalous areas influenced by the incomplete removing of relief effects.
The suggested procedure may be also successfully employed in analyzing the correlation degree between geophysical anomalies outlined by prospecting a zone using various methods (gravity and magnetism, for instance) or between any two physical elements.
Key words: correlation, Bouguer anomaly, Ditrau, computer programme.

THE GRAVITY DATA CONTRIBUTION FOR DELIMITATION
OF THE GURA SLANIC SALT DEPOSITS
Cristina Deaconu, F. Deaconu
Prospecting Company, Bucharest

Gravity prospecting (scale 1:5,000) carried out in 1989 in Tg. Ocna region outlined zones bearing salt accumulations (Gura Slanicului, Cucuieti) by minimum anomalies and pointed out the presence of tectonic features directly involving the existing structural relationship between salt accumulations and adjoing deposits.
The most important minimum anomaly was mapped in Gura Slanicului zone. It shows the eastward expansion if Gura Slanicului deposit. Drillings carried out, whose location was based upon gravity data, pointed out the existence of a new salt deposit in this zone.
Key words: gravity anomaly, salt, Gura Slanic region.

GRAVITY AND MAGNETIC SURVEYS CONTRIBUTION REGARDING
THE UNDERSTANDING OF DEEP STRUCTURE OF THE MOLDAVIAN
PLATFORM
Daniela Gorie, J. Gorie, S. Croitorescu
Prospecting Company, Bucharest

The geophysical surveys conducted in the north-east of the Moldavian Platform pointed out the structural relations between the crystalline basement and the covering sedimentary deposits and also between possible intrusive bodies included in the crystalline basement and the surroundings formations. Three possible models for the sources generating gravity and magnetic anomalies were considered and all three geological and structural resulting versions were analyzed. Thus, a few theories on the crystalline basement structure were evolved, based upon the latest gravity and magnetic data.
Key words: gravity, magnetic survey, Moldavian Platform, crystalline basement.

THE CONTRIBUTION OF GRAVITY, GEOCHEMICAL AND INDUCTED
POLARISATION DATA IN AN ATTEMPT TO ESTIMATE A NEW
ECONOMIC POTENTIAL OF THE JIRCA STRUCTURE
Ana Tudor, D. Tudor, C. Diaconescu
Prospecting Company, Bucharest

The integrated interpretation of geochemical, electrical and gravity data looked out for a better estimation of the economic potential of the area by yielding information regarding the relation between the undervolcanic major Jirca structure and the surrounding deposits. It has also emphasized data regarding the possible existence of intrusive bodies that could be associated with ore deposits pointed out by geochemical and electrical survey and by the already made drillings.
Key words: gravity survey, geochemical survey, induced polarisation survey, undervolcanic Jirca structure, intrusive bodies.

A NUMERICAL MODELLING OF THE TRANSIENT ELECTROMAGNETIC
RESPONSE OF A CONDUCTIVE ISOMETRIC BODY BY USING A SYSTEM
OF ELECTRICAL FILAMENT CIRCUITS
I. I. Stoica
Prospecting Company, Bucharest

A procedure is shown for the numerical modelling of TEM response of a conductive isomeric body by using a system of three electrical filamental circuits, RL type, which are not inductively coupled to each other. According to the procedure a programme for one loop version of the TEM method was implemented on the IBM PC compatible computer. The procedure of numerical modelling is calibrated above the body by using the exact quasisitatic solution of the sphere. The procedure is verified for some TEM physical scale modelling cases.
Key words: TEM numerical modelling, TEM physical scale modelling, TEM one loop version method, conductive isomeric body, electrical filamental circuit.

IIIrd Section: EARTH'S PHYSICS

NATIONAL GEODETIC NETWORK-LABORATORY FOR TESTING
MODERN GEODETIC EQUIPMENT AND TECHNOLOGIES
I. Popescu, N. Gulie, G. Loghin
Military Topographical Department, Bucharest

Designing rules and geodetical measurement achieved in this testing network are presented.
Processing methods are reviewed and appreciations about the quality of the obtained results are made.
Moreover, the possibilities offered by the national geodetic network for testing measuring and processing technologies in modern geodesy are enounced.
Key words: geodetical polygon, triangulation, levelling, gravitation, level difference, mean square error.

MAGNETIC DECLINATION SPATIAL VARIATION
IN EUROPE FOR 1950 – 1991 YEARS PERIOD
I. Radu
Military Topographical Department, Bucharest

The geographical distribution and variation of the magnetic declination in different intervals have been calculated, based on its annual average values analysis at more than 50 magnetic observatories. An algorithm for analytical estimations of magnetic declination and its variation is presented.
Maps of average declination for 5 years intervals between 1950 and 1990 were drawn up; including a map with predicted 1991.5 values. The declination values on the Romanian territory were fit in these maps as well.
Key words: magnetism, magnetic declination, Europe.

THE POSSIBILITY OF USING THE MODERN SYSTEMS OF COLLECTING
DATA IN THE LOCAL GEODETIC NETWORKS
E. Balint
Military Topographical Department, Bucharest

In this paper the existing modern systems of collecting geodetic data are presented and their possible use in local geodetic networks is analyzed.
The necessity of modifying the present technology of collecting and processing the data in local geodetic networks is analyzed too.
Key words: geodetic networks, geodetic data, systems of data collection.

TOPOGRAPHICAL MAP OF ROMANIA
Gh. Ciobanu, L. Gagea
Military Topographical Department, Bucharest

The topographical map of Romania has been made using the Gauss-Krüger projection for 1:25,000, 1:50,000, 1:100,000, 1:200,000 and 1:500,000 scales and the modified polyconical projection for 1:1,000,000.
The accuracy and content of land mapping is provided by the cartographical symbols and representation conditions.
The entire surface of the country is covered by the above-mentioned maps. Four basical colours are used for printing.
Key words: topographical map, cartographical projection, planimetry, relief, scale.

HEAT FLOW AND VELOCITY
OF Pn WAVE IN THE WESTERN BLACK SEA REGION
S. Veliciu, S. Spanoche
Institute of Geology and Geophysics, Bucharest

The dependence of the Pn-wave velocities, temperature and rocks composition in the Western Black Sea region was investigated. New and older heat flow data indicated values ranging from 32 to 92 mW/m depending upon different tectonic units: Black Sea basin, Moesian and Scythian platforms, Eastern Carpathians Alpine orogenic area.
A Pn-velocity map has been performed derived from the heat flow distribution. The main conclusion is that the temperature effect provides some explanations for the observed regional changes of the Pn velocities (from 7.8 to 8.2 km/s) related to the lateral inhomogeneities in the lower crust and upper mantle.
Key words: Black Sea, heat flow, velocity of seismic waves, tectonic origin.

GEOLOGICAL STRUCTURE F THE CARPATHIAN OROGEN AND
ITS FORELAND ALONG THE HRUIESTI – TARGU OCNA –
VLAHITA GEOTRAVERSE
M. Visarion, M. Sandulescu, D. Stanica, Maria Stanica, Ligia Atanasiu
Institute of Geology and Geophysics, Bucharest

The study of the geological and geophysical data along the Huruiesti – Targu Ocna – Vlahita geotraverse made possible the clearing up of the major structure of the units belonging to the Median Dacides, External Dacides and Moldavides and of their relationship with the foreland. The results obtained revealed the western extension of the underthrust platform elements up to a consumption paleoplane of the flysch nappes primary basement situated in the Neogene eruptive zone. The total thickness of the sedimentary formations attains 10 – 12 km, out of which 6 – 8 km represent the cover nappes thickness. The preliminary data supplied by magnetotelluric soundings point out significant variations of the depth of the high conductivity layer (HCL) from more than 150 km in the eastern segment of the profile to about 90 km west of the crust consumption paleoplane.
Key words: crust consumption paleoplane, underthrust platform elements, high conductivity layer.

DEEP STRUCTURE OF THE INNER CARPATHIANS IN THE
MARAMURES AND TISA AREAS (EAST CARPATHIANS)
M. Sandulescu, M. Visarion, D. Stanica, Maria Stanica, Ligia Atanasiu
Institute of Geology and Geophysics, Bucharest

The structural model elaborated on the basis of geological and geophysical data from Maramures and the Subcarpathian Ukraine reveals the existence of two consumption paleoplane of the primary basement of the flysch and pienine nappes, between which the sialic block corresponding to the Median Dacides is situated. The relative closeness of the two planes indicates the more restricted initial width of the Median Dacides as well as their transversal shortening. From west to east the separate blocks are characterized by different crust thicknesses: 25 – 26 km, 30 – 35 km, 50 – 52 km. The tectonic sketch elaborated points out the obvious bending of the Pienides in the terminal area in the Gutai-Maramures Mts determined by the tertiary overthrust of the Internal Dacides. The separation of the Babesti-Tiacev Nappe, consisting of Mesozoic formations and ophiolitic rocks, and the extension in the Romanian territory of the Kricevo Nappe represent clearly a novelty.
Key words: crust consumption paleoplane.

DATA CONCERNING SEISMIC MICROZONING OF BUCHAREST
N. Mandrescu
Center of Earth Physics, Bucharest – Magurele

During the last fifty years, three large intermediate-depth earthquakes occurred in the Vrancea region, in 1940 (M = 7.4), 1977 (M = 7.2) and 1986 (M = 7.0). The first two above-mentioned earthquakes have caused huge damage in Bucharest. The 1986 earthquake has a particular importance due to the fact that it triggered more than fifty strong motion accelerographs from the Romanian network. The paper attempts to review the available data concerning the effects of the mentioned earthquakes in Bucharest and to compare them with the seismic microzoning maps.
Key words: intermediate-depth earthquake, seismic microzoning, strong motion.

ANALYSIS OF THE SEISMICITY
IN THE FOCSANI – RAMNICU SARAT REGION
Luminita Ardeleanu, V. Smalbergher
Center of Earth Physics, Bucharest – Magurele

The Focsani – Ramnicu Sarat zone, situated outside the Carpathian Arc, has a complex geological structure characterized by active seismic faults.
A very homogeneous and complete data set is obtained for the period March 1977 – December 1988 (magnitude threshold ML = 2.5).
The paper attempts to model the seismic activity using a parameterization related to the earthquake interactions and derived from the Weilbull distribution function.
Key words: Focsani – Ramnicu Sarat seismic region, seismic activity, seismicity, patterns.

A NEW PROCESSING AND EDITING MANNER OF THE SURLARI
OBSERVATORY DATA
Alexandra Ionescu, Gabriela Cucu, Ramona Plavita
Institute of Geology and Geophysics, Bucharest

The minute mean data of the H, D, Z components of geomagnetic field are recorded on 5.25 inch floppy disks, with the sensitivity of 1nT/nm, due to the digital recording system DIMARS. The processing programs are suitable for the PC – IBM computer supplied together with the recording system. The final result is the Observatory Yearbook ready to be sent to the World Data Centers in the IAGA formats and to the geomagnetic world-wide network observatories.
Key words: DIMARS, geomagnetic field, programmes, IAGA format.

SOME PECULIARITIES OF THE CRUSTAL SEISMIC REFLECTIVITY
IN THE WEST FALTICENI AND NORTH-WEST PITESTI ZONES
V. Varodin1, V. Raileanu2, D. Talos1, D. Stiopol1, V. Dumitrescu1, D. Mateiciuc2
1Prospecting Company, Bucharest
2Center of Earth Physics, Bucharest – Magurele

Two deep reflection seismic profiles situated in the Carpathian Foredeep in the west Falticeni (F) and in the north-west Pitesti (P) ones, with 15 seconds two time way rcorded are presented.
Each profile gives deep information, everyone reflecting crustal peculiarities about the investigated seismic line.
The F profile shows a lower crust with high seismic reflectivity, in opposition with the upper crust which is less reflective, while P profile illustrates a continuous decrease in the crustal seismic reflectivity versus depth.
A quantification of seismic reflectivity versus depth is tried, then it is compared with the local heat flow. A diminution in crustal seismic reflectivity with the heat flow decreasing is found.
The resulted crustal patterns of the two processed seismic profiles are presented finally.
Key words: deep seismics, (continental) crust, seismic reflectivity, heat flow.

SEISMIC VELOCITY DISTRIBUTION IN THE LITHOSPHERE
OF VRANCEA REGION
M. Anghel, F. Radulescu, V. Smalbergher
Center of Earth Physics, Bucharest – Magurele

The intermediate earthquakes produced in the Vrancea region, below the Vrancioaia seismological station, in the period 1980 – 1987 were analyzed. The seismic velocity distribution in the underground of this region at depths of 65 – 160 km, was determined by using arrival times of P and S seismic waves. The analysis of these earthquakes showed an important decreasing of velocity from the depth of 100 km, where authors considered the top of the asthenospheric layer. So, variation of the ratio VP/VS, and the Poisson coefficient in time and in space are presented.
Key words: intermediate earthquake, lithosphere, P and S seismic waves, velocity depth distribution.

GLOBAL POSITIONING IN GPS SYSTEM USING RECEIVERS AS TERMINALS
IN SHORT BASE INTERFEROMETRY BY DOPPLER OBSERVATIONS
I. Radu, Monica Rotaru, Liana Filip
Military Topographical Department, Bucharest

The Global Positioning System can be used for geodetical purpose by using Doppler observations when the code (C/A and P) are unknown.
These kinds of measurements can be used only in relative positioning.
An algorithm for processing GPS data in this case is presented.
Key words: GPS system, relative positioning, Doppler positioning.

SOME ASPECTS OF USING THE TIME IN THE ROMANIAN GEODETICAL
DOPPLER SYSTEM (DOGER) FOR THE GLOBAL GEOMETRIC POSITIONING
I. Radu, Monica Rotaru, Liana Filip, I. David
Military Topographical Department, Bucharest

The necessary accuracy for geodetic positioning in the establishing Doppler counts making up time is presented after time scales definition.
The time intervals at different arrival time of the information in the system floors are defined.
Key words: Doppler positioning, time system.

HIGH ACCURACY REPEATED LEVELMENT ON RAMNICU-SARAT –
MARASESTI AND FOCSANI – TARGU SECUIESC PROFILES
V. Dragomir, Dorel Zugravescu, Ileana Fatulescu
Institute of Geodynamics of the Romanian Academy, Bucharest

The high accuracy repeated levelment (1.5 mm/km) made between March 1989 – November 1991 in conditions imposed by the characteristics of the geodynamic studies on the judiciously selected profiles in Vrancea zone has confirmed the existence of some relative displacements of the tectonic compartments of several centimeters per year. The jump of 5 cm/6 months in the Colacu – Valea Sarii zone, observed between the measurements made before and after the May 30th, 1990 earthquake has to be mentioned.
Key words: high accuracy repeated levelment, Vrancea zone, relative displacements, geodynamics, crust deformations.

VRANCEA – AN ACTIVE GEODYNAMIC ZONE; PECULIARITIES
OF THE HIGH ACCURACY LEVELMENT
Dorel Zugravescu, V. Dragomir, Ileana Fatulescu
Institute of Geodynamics of the Romanian Academy, Bucharest

The relative displacement between tectonic compartments in the Vrancea zone is evidenced by reinterpreting the information with implicit geonomical value contained in the raw data of the high accuracy repeated levelment. The order of magnitude of these displacements, which in certain zones can reach some cm/year, leads to a new vision concerning the way which the Ist order repeated levelment should be planned. In the same time it becomes an important criterion to discriminate the models trying to explain the dynamics of the zone.
Key words: high accuracy repeated levelment, Vrancea zone, relative displacements, crust deformations.

THE DEALUL PISCULUI – CALDARUSANI ASTROGEODYNAMIC POLYGON
Dorel Zugravescu1, Marian Rotaru2
1Institute of Geodynamics of the Romanian Academy, Bucharest
2Topographic Military Department, Bucharest

Completing of the Dealul Piscului Astronomic observatory with equipment devoted to continuously monitoring the crust deformation, doing repeated astro-geodetical measurements in the Caldarusani – Gruiu Geodynamic Polygon, connecting by systematically repeated gravimetric measurements the Dealul Pisculuui and Caldarusani observatories, as well as including of the two observatories in the Global Positioning System, make the Astronomic Dealul Piscului and Geodynamic Caldarusani Observatories basic elements of an Astrogeodynamic Polygon, which can bring important contributions to the surveying of the phenomena causally connected with the geodynamic active Vrancea zone.
Key words: crust deformation, astro-geodetic measurements, repeated gravimetric measurements, Global Positioning System.

ON THE GENERALITY OF THE MATERIALS FRAGMENTATION LAW:
IMPLICATIONS IN GEODYNAMICS
F. Munteanu1, Dorel Zugravescu1, M. Rusu2, C. Suteanu1
1Institute of Geodynamics of the Romanian Academy, Bucharest
2Bucharest University, Faculty of Physics, Bucharest

Lately, many researches regarding the ruptures mechanics have had as object of study some peculiarities of the rupture processes that seem to prove the existence of some evolution laws, irrespective of the kind of material. In this context, one of the research directions, with direct implications in Geodynamics modelling has in view the way the fragmentation process develops.
Starting from the experimental results in literature, partially acknowledged by own experiments, this paper presents a dichotomic, quasialeatory model of recursive dividing if a whole, as well as the peculiarities regarding the geometric structure and the statistic distribution of the obtained parts, that are specific for this model.
The satisfactory agreement between the model and the experimental data, as well as the facility of widening the understanding in this way regarding the mechanisms the fragmentation processes are based on, suggests the opportunity to continue the refining and completing efforts of this model.
Key words: fragmentation, hierarchization, self-structuring, self-similarity, fractals.

ON A POSSIBLE GEODYNAMIC ORIGIN IN THE 1/f NOISE
IN THE ELECTRONIC SYSTEMS
F. Munteanu1, Dorel Zugravescu1, M. Rusu2
1Institute of Geodynamics of the Romanian Academy, Bucharest
2Bucharest University, Faculty of Physics, Bucharest

The recent both theoretical and experimental researches regarding the fractal structure of the solid matter, suggests the hypothesis of a hierarchical distribution of the masses, that manifest themselves dynamically by means of a vibration spectrum of 1/f type.
Considering a mechanical-electrical coupling, it can be said that the mechanic dynamics of the solid structures will also determine an electromagnetic noise of the same type 1/f; (0.8 – 1.2). The weak shielding of the passive or active electronic devices for low frequencies (f 100 Hz), as well as the identification of the 1/f type noise in systems with different operational principles, makes that at least theoretically, part of the noise has a reason external to the studied system.
Structured as mentioned above, this paper presents the theoretical and experimental context in which the electrical type noise produced in the active electronic devices was studied, as well as some preliminary results, suggesting the use of this phenomenon in the estimation of some geodynamic phenomena.
Key words: hierarchy, fractal, 1/f noise, deterministic chaos.

REGARDING THE FACILITY OF USING THE FEIGENBAUM SCENARIO
IN MODELLING SOME GEODYNAMIC PHENOMENA
F. Munteanu, Dorel Zugravescu, C. Ioana, C. Suteanu
Institute of Geodynamics of the Romanian Academy, Bucharest

The discovering by Feigenbaum of the chaos transition scenario, as well as its experimental checking in the case of the biogeophysical processes have generated a new paradigm in the study of Nature. The evolution of the meeorological phenomena, the turbulent flow, the spatial-temporal distribution of earthquakes, the heart rhythm and many other processes, considered up to now as having a random evolution, have entered the category of chaotic phenomena and benefit from a specific mathematical modelling.
This paper presents some peculiarities of the Feigenbaum scenario, insisting upon the study of convergent subrows, generated in the bifurcation process. An estimator of the "dynamic behavior" is defined: the convergence speed and its dependence of the initial value. An algorithm is proposed able to identify whether a digital series was generated by means of the basic scenario: Xn+1 = Xn[1+k(1–Xn)] and references are made to the peculiarities implied by experimental application of geophysical phenomena modelling, relying on recursive methods.
Key words: random, chaotic, bifurcation, convergence speed.

COMPLEXITY SCIENCE – AN INTEGRATING VISION ON
THE BIOGEODYNAMIC REALITY
F. Munteanu
Institute of Geodynamics of the Romanian Academy, Bucharest

The results of the last decades regarding the nonlinear treatment of the Nature phenomena, the constituting of some synthesis branches as: synergetics, complexity physics, catastrophies theory, the issuing of some more convenient mathematical models for the description of the surrounding reality: fractals, chaos transition theory, as well as of the cell automata and neuronal computers have allowed the scientific unitary approach of the triangle: information, energy matter, creating the frame for a synthesis of the knowledge acquired by mankind from immemorial times up to now.
This paper tries to define the complexity science as discipline studying the universe fundamental unity, in which the observer and the observed object are placed in a permanent movement and mutual change.
Key words: synergy, fractals, cell automata, selforganizing.

SHALLOW DEPTH WATERS MAGNETIC IN NORTHERN DOBRUDJA - RAZIM LAKE
I. Besutiu, Vl. Rosca, A. Nicolescu, Cr. Gavriliu, I. Petrisor
Institute of Geology and Geophysics, Bucharest

Shallow depth waters magnetics for the achievement of a comprehensive magnetic map of Northern Dobrudja went on during 1989 and 1990 years by mapping the western part of Razim Lake.
The performed maps, T and Ta, have permitted the statement of some pioneer hypothesis concerning the geological structure of the investigated area. Major contacts between the main geological units have been revealed within the water covered area. An interesting N – S faults system is also pointed out. Basement uplift region as Unirea-Dolosman, Tasburun-Iancila and Popina Island alterate with depressions filled by thick sediments, perspective areas for oil accumulations.
Key words: magnetics, magnetic maps, shallow depth waters, Northern Dobrudja, oil.

CRUSTAL VERTICAL MOVEMENTS IN THE PORTILE DE FIER REGION
R. Radulescu1, I. Buse2, V. Nacu1, M. Biter1
1Center of Earth Physics, Bucharest – Magurele
2Institute of Geodesy, Photogrammetry, Cartography and Land Management, Bucharest

The results of high accuracy levelling measurements performed along the Danube (Socol – Izvoarele sector) in 1978, 1983 and 1988 were analysed. The annual average velocity of the vertical movement for three periods between measurements, in correlation with the geological structure is presented. These data shown different geodynamic regime of various crystalline and sedimentary areas of the Southern Carpathians and the Carpathian Foredeep too. Transition zones from uplift movements to strong subsidence movements suggest the presence of some deep faults, of which the fracture between the Carpathian and Moesian basement has a geodynamic importance.
Key words: geometric levelling, velocity of vertical movement, geodynamic regime.

VECTORS OF HORIZONTAL GRADIENTS OF CRUSTAL MOVEMENTS IN ROMANIA
V. I. Mocanu1, F. Radulescu2
1Bucharest University, Faculty of Geology and Geophysics, Bucharest
1Center of Earth Physics, Bucharest – Magurele

A map of horizontal gradients of vertical movements velocity was, for the first time, carried out for the Romanian territory. The authors utilized the velocity values of second variant of the national map of recent crustal movements, scale 1:1,000,000 elaborated in 1986. Respective calculations made in points of a square net of 10 km using the Thurm's method. Geodynamic elements of this map were correlated with important tectonic areas and lines of Romania.
Key words: Geodynamics, map vectors of vertical movements, Romania, national geodetic network.

ESTABLISHING SPACE DEVELOPMENT OF WEAK MAGNETIC SOURCES
THROUGH MAGNETIC GRADIENT INTERPRETATION
D. Onescu, D. Hannich
Prospecting Company, Bucharest

It is possible to detect weak magnetic sources, through magnetic gradient measurements in weak magnetic fields, in the situation of ore deposits, localized in strongly hydrothermal magnetic rocks, in the Micanesti – Cerbia zone (Metaliferi Mountains).
The paper presents a comparison of magnetic gradient field measurements with computed gradient data, by means of the Cosntantinescu-Eldaiem method. The measured and computed data, presented in two maps, offer a good approach.
Key words: magnetic gradient, weak magnetic sources, interpretation.

PALEOMAGNETISM OF UPPER CRETACEOUS MAGMATIC ROCKS
IN THE BANAT AREA (ROMANIA)
St. Patrascu1, C. Panaiotu2
1Bucharest University, Faculty of Physics, Bucharest, Romania
2Institute of Geodynamics, Bucharest

Forty four sites were sampled for this study in the western part of the Southern Carpathians. After detailed AF demagnetization only 10 sites yielded primary remanent magnetizations, in the directions of which are similar to those identified in Senonian magmatic rocks from the Apuseni Mountains and Hateg and Rusca Montana Basins. The mean paleomagnetic pole for these three areas is compared with those form coeval formations of stable Europe and stable Africa. This comparison shows a large clockwise rotation with respect to Africa and Europe and a northward transport to reach their present-day position during the Tertiary.
Key words: paleomagnetism, Banat, tectonic implications

CARPATHIAN CONDUCTIVITY ANOMALY AND ITS RELATION
TO DEEP STRUCTURE
E Pinna1, A. Soare2, D. Stanica2, Maria Stanica2
1Earth's Science Department, Univ. of Pisa, Italy
2Institute of Geology and Geophysics, Bucharest, Romania

The Carpathian electrical conductivity anomaly (CECA) has been approximately marked on the Wiese induction arrows map and discussed in many papers since 1963, when it was related for the first time by Wiese. In this paper, after the description of a new geographical position of the CECA, some hypotheses on its origin, taking into account the distorsions of the magnetotelluric sounding curves in connection with geotectonic relation and other geophysical data, are presented.
Key words: Electrical conductivity, Wiese induction arrows, magnetotelluric sounding, Carpathians.

STRUCTURAL MODEL FOR THE GODEANU MASSIF DEDUCED FROM
THE MAGNETIC COMPONENT VALUES OF THE NATURAL
ELECTROMAGNETIC FIELD
V. Furnica, Cornelia Furnica
Institute of Geology and Geophysics, Bucharest

Supposing the spatial structure of the original electromagntic field is known, its source being considered an arc current, it is possible to determine, based on the relationships dependent on the variable geomagnetic field components, the electrical properties of the geological structure, over which the magnetic vector is measured. The adaptation to the conditions of our country represents the new element introduced by this work. The application was carried out on two magnetotelluric sounding profiles crossing the Godeanu Massif, achieved in 1989.
Key words: variable geomagnetic field, profiles with magnetotelluric sounding, Godeanu Massif.

A NORMAL FIELD FOR THE ROMANIAN SECTOR OF THE BLACK SEA SHELF
C. Demetrescu1, R. G. Dimitriu2, C. S. Sava2, Maria Andreescu1
1Institute of Geodynamics, Bucharest
2Institute of Geology and Geophysics, Bucharest

The normal geomagnetic field for the Romanian Black Sea shelf, epoch 1985.0, adopted as reference level for the magnetic survey of the area of the scale 1:200,000, is presented. The optimum variant has been chosen by analyzing the advantages and drawbacks of several candidates. Advantages related to the larger area of validity and possibilities of direct comparison with measurements on land and on future marine panels, made us suggest the International Geomagnetic Reference Field as the beast variant. For the study area, an additional "crustal field", also given in the paper, might be used, as an option, to remove a weak remnant regional variation.
Key words: geomagnetic exploration, reference field, shelf, Black Sea, Romania.