Chairman: Prof. LIVIU CONSTANTINESCU, corresponding member of the Academy
MODELS OF THE LITHOSPHERIC STRUCTURE ON THE ROMANIAN TERRITORY
C. DEMETRESCU, MARIA ANDREESCU, M. ENE, F. RADULESCU, M. BITER, V. RAILEANU
Center for Earth Physics and Seismology Bucharest – Magurele
The lithospheric structure along the Galati – Chisinau Cris and Iasi – Turnu
Magurele profiles was investigated by using mainly deep seismic sounding and
heat flow data. Notable lateral differences of the crustal structure and of
the thermal structure of the lithospheric were rendered evident and discussed.
Key words: lithosphere, crust, structure, heat flow, deep seismic sounding,
Romania.
THERMAL CONVECTION AND HEAT BUDGET IN SOME GEOTHERMAL SYSTEMS FROM ROMANIA
H. MITROFAN, RODICA FIRAN
The paper is presented in extenso in this issue, page. 23.
SOME ASPECTS OF DATA INTEGRATION OF THE SURLARI GEOMAGNETIC OBSERVATORY
INTO THE EUROPEAN OBSREVATORY NETWORK
A. SOARE, A. COSMA, ALEXANDRA IONESCU
Institute of Geology and Geophysics, Bucharest
Some aspects of "momentary values" analysis at the Surlari Geomagnetic
Observatory are presented. They are correlated with similar data from other
14 European observatories, in order to establish the absolute level of the
recordings.
Key words: momentary values, geomagnetic observatory, absolute level.
A WAY TO OUTLINE SOME REGIONAL AND LOCAL PECULIARITIES OF THE LONG PERIOD
GEOMAGNETIC VARIATIONS
A. COSMA
Institute of Geology and Geophysics, Bucharest
A possible source of long period geomagnetic variations through a circular
current loop is modelled on the basis of data from 14 European geomagnetic
observatories.
Key words: geomagnetic variations, model, circular current loop.
SECULAR VARIATION OF THE GEOMAGNETIC FIELD REFLECTED
IN THE VERTICAL COMPONENT MAGNETIC MAP ON THE
ROMANIAN TERRITORIY
L. BESUTIU, GEORGETA BESUTIU
Institute of Geology and Geophysics, Bucharest
The preliminary results obtained within the framework of the national magnetic
reference network have allowed an analysis of the general deformations of the
geomagnetic field – in the 
Z
and Za
images – due to the secular
variation, by confronting the field values determined within the network with
those offered by the national magnetic map.
The consequences of an incorrect choice of the normal field formulae are also
discussed.
Key words: geomagnetic field, secular variations, broadscale magnetic map,
Romania.
GEOMAGNETIC EXCURSIONS – METHODOLOGIES OF INVESTIGATION, APPLICATION
SORIN RADAN, MARIA RADAN
Institute of Geology and Geophysics, Bucharest
The detailed study of the geomagnetic field variations during the Brunhes
normal polarity epoch emphasized a number of "paleomagnetic anomalies" or "geomagnetic
excursions". With the purpose of their identification some specific sampling
methods were used which are discussed in detail in the central part of the
paper. Finally, some preliminary results obtained by the authors on some Quaternary
sedimentary formations are presented.
Key words: geomagnetic excursion, Quaternary period, Brunhes epoch, sedimentary
formations, samplind method.
STATISTICAL ANALYSIS APPLIED TO DATA DERIVED FROM
A VISUAL INTERPRETATION OF LANDSAT IMAGES IN ORDER TO
IMPROVE THE EXTRACTABLE INFORMATION
DANA FEKETE, C. NITICA
Institute of Geology and Geophysics, Bucharest
In the first stage the lineaments maps were obtained from the interpretation
of the LANDSAT images in the western part of the South Carpathians. Statistical
analysis of these maps led to new elements which describe the spatial distribution
of the identified lineaments, improving the objectiveness of the information
obtained.
Key words: remote sensing, statistical analysis, LANDSAT image, lineament.
DEEP STRUCTURE IN EASTERN ROMANIA AS DETERMINED BY THE MAGNETOTELLURIC
METHOD
D. STANICA, MARIA STANICA
Institute of Geology and Geophysics, Bucharest
Magnetotelluric researches carried out along two profiles crossing the Eastern
Carpathians give new information on the electrical conductivity distribution
within the crust and upper mantle.
The magnetotelluric soundings reveal the crystalline basement at depths from
the Earth's surface to 15 km and the upper limit of the asthenosphere in the
deep ranges from 80 to 300 km.
Key words: astenosphere, electrical conductivity, magnetometric sounding.
STUDY OF THE TILTS OF THE EARTH'S CRUST AT THE PADES-GORJ AND
CRACIUNESTI-DEVA UNDERGROUND OBSERVATORIES, ROMANIA
(1 JANUARY 1979 – 30 JUNE 1984)
DOREL ZUGRAVESCU1, D. DELION1, ILEANA FATULESCU1,
R. DOROBANTU1, MANUELA CALINESCU2
1Centre for Earth Physics and Seismology Department of Geodynamics, Bucharest
2Enterprise of Geological and Geophysical Surveys, Bucharest
The Earth's crust tilts, computed as derivatives of actually recorded values,
point out for both observatories, some preferential directions along which
they can be observed in a certain period: a characteristic feature is the fact
that although the orientations of these directions have a time evolution for
both observatories, they remain perpendicular to each another.
Key words: geodynamics, tiltmetric tides, Earth's crust tilt, underground observatory,
angular distribution.
REAL TIME FACILITIES PROGRAMMING LANGUAGE FOR DATA ACQUISITION AND STORAGE
MICROSYSTEM
D. DELION, V. GHEMIGIAN, DOREL ZUGRAVESCU, R. DOROBANTU
Center for Earth Physics and Seismology, Department of Geodynamics, Bucharest
Written on three levels each of them subordonating the preceding ones and
allowing to be used as an independent language, the software structure of the
microsystem, for the on-line acquisition and processing of the geodynamic data,
is built on an 8-bit microprocessor.
The programming of the real time processes (acquisition and preliminary data
processing) as well as the command of feedbacks (drift corrections) are possible
in this way.
Key words: geodynamics, Earth tides, data acquisition system, programming language,
direct memory acces.
THERMAL CONDUCTIVITY OF THE MARINE SEDIMENTS
DETERMINED BY THE THERMISTOR DIGITAL THERMOGRAPH
DEVOTED TO EQUIP GEODYNAMIC OBSERVATORIES (TTGO)
C. DEMETRESCU1, DOREL ZUGRAVESCU1, R. DOROBANTU2, O. HARADJA1
1Center for Earth Physics and Seismology, Group of Natural Fields, Bucharest – Magurele
2Center for Earth Physics and Seismology, Department of Geodynamics, Bucharst
The use of TTGO in transitory thermal regime in determining the thermal conductivity
of marine sediments, offers the following advantages:
– existence of an internal tact assuring the carrying out of temperature
measurements at required time intervals;
– possibility to display and/or store information;
– possibility to calibrate the recording with a 103 °C resolution-along
the entire measuring range.
Key words: thermal conductivity, digital thermograph, marine sediments, geodynamic
observatory.
TESTING AND AGEING WITHIN THE FRAMEWORK OF LCAGA OF THE DZ – 03 TYPE
HORIZONTAL QUARTZ PENDULUM RESPECTIVELY OF THE HORIZONAL AND VERTICAL QUARTZ PENDULA EQUIPPED WITH A CAPACITIVE TRANSDUCER
DOREL ZUGRAVESCU1, R. DOROBANTU1,
N. PUSCASU2, ILEANA FATULESCU1, D. DELION1
1Center for Earth Physics and Seismology, Department of Geodynamics, Bucharest
2Enterprise of Geological Surveys and Exploration "Oltenia", Craiova
The functional parameters of the realized clinographs were compared with
those of the DZ – 01 and DZ – 02 type quartz clinographs.
The functional parameters of the capacitive transducer equipping horizontal
and vertical quartz pendula were established by the testing system (SFPCT).
The calibrating of all these devices is carried out within the framework of
the Laboratory of calibration and ageing of the geodynamical apparatus (LCAGA)
under the influence of the artificial vibrations produced by the activity of
the Bucharest town.
Key words: geodynamic instruments, tiltmetric Earth tides, crust deformations,
underground observatory, clinograph, capacitive transducer.
NEW RESULTS IN SEISMIC DIRECTIVITY OF MULTISHOCK SOURCES AND THEIR IMPORTANCE
IN SEISMIC RISK STUDIES
I. CORNEA, M. MISICU, M. C. ONCESCU
Center for Earth Physics and Seismology, Bucharest – Magurele
On the base of directivity and isochronism studies of seismic waves radiated
by multishock sources, as that of March 4, 1977 from Vrancea region, new data
concerning the superposition of seismic oscillations were obtained. These results
permit a better design of resistance structures in the investigated zone.
Key words: seismic risk, seismic directivity
DETERMINATION OF THE HYPOCENTRAL PARAMETERS OF TELESEISMIC
EVENTS BY USING THE ROMANIAN TELEMETRED SEISMIC NETWORK
V. BURLACU, VICTORIA OANCEA, OLIVIA BAZACLIU
Center for Earth Physics and Seismology, Bucharest – Magurele
A method for computing the origin time and the epicentral coordinates of
teleseismic events recorded by Romania's telemetred seismic network was developed,
by using the P wave arrival times. The computation procedure was applied to
different teleseisms stored on magnetic tapes.
Key words: hypocentral parameters, teleseismic event, seismic network.
CHARACTERISTICS OF THE SECULAR VARIATION OF THE GEOMAGNETIC FIELD DURING
THE LAST 20 YEARS IN ROMANIA
C. DEMETRESCU1, MARIA ANDREESCU1, T. NESTIANU2, M. ENE1
1Center for Earth Physics and Seismology, Bucharest – Magurele
2Institute of Geology and Geophysics, Bucharest
The variation of the H, Z and T components of the geomagnetic field at repeat
situations on the Romanian territory between 1964 and 1981 is discussed in
terms of the interval variation and the related to the solar cycle. Their geographical
distribution is accounted for by the magnetic and electric structures of the
interior of the Earth. The effects of magnetic and electromagnetic induction
caused by the variation related to the solar cycle.
Key words: secular variation, magnetic induction, deep structure, Romania.
TEMPORAL FLUCTUATION OF P-WAVES SECOND ORDER RESIDUALS FOR VRANCEA EARTHQUAKES
AND ITS PREDICTIVE CHARACTER
SIEGLINDE IOSIF, T. IOSIF, M. C. ONCESCU
Center for Earth Physics and Seismology, Bucharest – Magurele
The study of second order of P waves generated by Vrancea earthquakes emphasizes
the temporal fluctuation of seismic velocity and stress accumulation within
the zone, which represents important precursors for a short-term earthquake
prediction.
Key words: temporal fluctuation, second order residuals, stress accumulation,
earthquake prediction.
ROMANIA'S HORIZONTAL GRADIENT AND CURVATURE MAPS OF RECENT CRUSTAL MOVEMENTS
S. MANTU
Center for Earth Physics and Seismology, Bucharest – Magurele
Maps of horizontal gradients and mean curvature of vertical recent crustal
movements are drawn in order to emphasize the behavior of the earth's crust.
Key words: recent crustal movements, gradient, curvature.
ACTIVE TECTONIC BEHAVIOUR OF SEVERAL FAULTS IN SOUTHERN ROMANIA
S. MANTU1, ELENA MANTU2
1Center for Earth Physics and Seismology, Bucharest – Magurele
2School 46, Bucharest
The spatial analysis of recent crustal movement velocities along the Orsova – Calarasi
line emphasizes an increased tectonic activity in the areas of the Olt's embouchure
and Calarasi, corresponding to the crossing of the Olt and Calarasi faults
by the measurement line.
Key words: recent crustal movements, earth crust, tectonic activity.
SOURCE AND ATTENUATION EFFECTS ON SEISMIC CODE WAVES OF LOCAL EARTHQUAKES
VICTORIA OANCEA, V. BURLACU, OLIVIA BAZACLIU
Center for Earth Physics and Seismology, Bucharest – Magurele
The effects of attenuation, excitation and radiation at the source on the
seismic coda waves are analysed.
A scaling law of the earthquake source spectrum is obtained by using the spectral
ratios of coda source factors.
Key words: coda waves, source spectrum, attenuation, scaling law.
RECENT RESULTS CONCERNING THE DEEP STRUCTURE OF VRANCEA REGION
M. C. ONCESCU
Center for Earth Physics and Seismology, Bucharest – Magurele
Vhe results of simultaneous inversion for hypocenters and 3-d velocity structure
in Vrancea region, as well as those of relocations using the "master event" technique
led to two modifications in the tectonic model proposed by Fuchs et al. (1979):
a) the intermediate seismic activity occurs at the limit of separation between
the decoupled slab and the rest of the NE – SW paleosubduction;
b) the relative motion toward NW of the Black sea platelet "helped" the
decoupling of the lithospheric slab.
Key words: 3-D velocity structure, earthquake relocation, tectonics of Vrancea
region.
SOME CHANGES TO THE ASTRONOMICALA REFERENCE SYSTEM AND THEIR EFFECTS ON
COORDINATE TRANSFORMATIONS
RADU C. ION
Military Topographic Direction, Bucharest
The changes in defining the astronomical reference system are based upon
a number of resolutions passed by the International Astronomical Union (I.A.U.)
at previous meetings. They include six recommendations which will affect the
satellites ephemeris generations.
Key words: reference system, coordinate frame, tracking data, standard epoch,
precession mutation, apparent sideral time, polar motion, transformation matrices.
THE VRANCEA INTERMEDIATE-DEPTH EARTHQUAKES AND THE PECULIARITIES
OF THE SEISMIC INTENSITY DISTRIBUTION OVER THE ROMANIAN TERRITORY
N. MANDRESCU, M. ANGHEL, V. SMALBERGhER
Center for Earth Physics and Seismology, Bucharest – Magurele
On the basis of the isoseismal maps of the largest Vrancea intermediate-depth
earthquakes, occurred between 1893 and 1977, a map of maximum seismic intensity
has been compiled.
The map points out the influence of source mechanism and site conditions, on
the seismic effect distribution over the extra-Carpathian territory.
Key words: intermediate-depth earthquake, seismic intensity, attenuation, site
effect.
AUTOMATED METHOD IN DETERMINING THE FAULT'S PARAMETERS BY USING GRAVITY
DATA
D. V. STEFLEA
Center for Earth Physics and Seismology, Bucharest – Magurele
The first and second horizontal derivatives and the first vertical derivative
are calculated from a gravity profile over a geological contact. By plotting
the horizontal derivative against the vertical derivative, a number of specific
points are determined and it is possible to obtain the angle of dip, the depths
to the upper and lower faces and the density contrast.
Key words: faults, gravity data interpretation, automated methods
TEMPORARY CHANGES OF ELECTROMAGNETIC INDUCTION AT SURLARI GEOPHYSICAL OBSERVATORY
A. SOARE
Institute of Geology and Geophysics
Some data on the transfer function variations for the geoelectromagnetic
field at the Surlari Geophysical Observatory are presented. The possibility
of their application to the tectonomagnetic event detection, after the filtering
of the instability caused by the external field sources is analysed.
Key words: induction vectors, external sources, geoelectromagnetic field.
DETERMINATION OF THE SEISMIC MOMENT TENSOR FROM SHORT PERIOD BODY WAVES.
APPLICATION TO INTERMEDIATE VRANCEA EARTHQUAKES
M. C. ONCESCU, C. I. TRIFU
Center for Earth Physics and Seismology, Bucharest – Magurele
An original, robust and efficient method to determine the seismic moment
tensor from long period levels of body wave displacement spectra – with
the signs of first motions associated, was developed. The method was applied
to several tens of Vrancea intermediate earthquakes, assuming several source
models.
Key words: seismic moment tensor, intermediate earthquakes, Vrancea region.
SEISMIC RESPONSE TO LOCAL GEOLOGICAL STRUCTURE TO PLANE WAVES
M. RADULIAN
Center for Earth Physics and Seismology, Bucharest – Magurele
The local structure effects on ground motion are determined for vertically
incident P, SH and SV waves. The solution of seismic wave propagation problem
in laterally inhomogeneous media is given by using the finite difference method.
Only two-dimensional models are considered. The effects due to sedimentary
basins, alluvial valleys and topography are particularly analysed.
Key words: local response, lateral inhomogeneity, finite difference method,
two-dimensional model.
CHARACTERISTICS OF NEAR FIELD GROUND MOTION FOR CRACK SOURCE MODELS
C. I. TRIFU, M. RADULIAN
Center for Earth Physics and Seismology, Bucharest – Magurele
Ground motion on fault and in the near field is analysed based on a two-dimensional
stress-drop source model. The obtained results are compared with some others
known in literature and both advantages and restrictions of the proposed model
are emphasized when used for near field dynamic studies.
Key words: seismic source, crack model, near field, synthetic accelerograms.
COMPARISON OF THE RECORDING BASE LEVELS AT THE SURLARI (SRR)
NIEMEGK (GDR) AND HURBANOVO (CSR) OBSERVATORIES
C. DEMETRESCU1, ALEXANDRA IONESCU2, T. NESTIANU2
1Center for Earth Physics and Seismology, Bucharest – Magurele
2Institute of Geology and Geophysics, Bucharest
On the basis of the comparison measurements results, made in October 1984
at Hurbanovo (CSR), the differences between the recording base level of the
Surlari, Niemegk and Hurbanovo observatories are presented.
Some considerations concerning the drift of the main constant of the quartz
horizontal magnetometer (QHM) are made.
Key words: base level, drift, magnetometer, Surlari, Niemegk, Hurbanovo.
UPPER ATMOSPHERE DENSITY AND TEMPERATURE FROM THE MOTION OF THE SATELLITES
POLIOT 1 AND SAMOS 2
MAGDALENA CRASMARU, IRINA PREDEANU, T. OPROIU
Center of Astronomy and Space Sciences, Bucharest
The upper atmosphere density at heights between 200 and 400 km is computed
from orbital drag data of the satellites 1963.043.01 – Poliot 1 and 1961.001.01 – Samos
2. The exospheric temperature corresponding to the observed density is also
determined. The results are compared to the values given by the models CIRA – 72
and DTM. Some conclusions concerning the improvement of the atmospheric model
are drawn.
Key words: aeronomy, upper atmosphere, parameters, satellite orbit analysis,
Poliot 1, Samos 2, CIRA – 72 model, DTM model.
TOTAL OZONE DISTRIBUTION AT BUCHAREST
M. FRIMESCU, LAURA MANEA
Institute of Meteorology and Hydrology, Bucharest
Based upon total ozone measurements made by means of Dobson spectrophotometer
the main variations of this atmospheric parameter were established.
The contribution of the Romanian ozone station to the Global Ozone Research
and Monotoring Project initiated by W.M.O. and to the European Correlation
Programme between the strathospheric warmings and great ozone variations are
also presented.
Key words: total ozone, Dobson spectrophotometer, stratospheric warmings.
THEORETICAL MODELS FOR THE FREE SURFACE DISPLACEMENT PRODUCED BY FAULT
MOVEMENTS
D. V. STEFLEA, DORINA DANCHIV
Center for Earth Physics and Seismology, Bucharest – Magurele
The paper is presented in extenso in this issue, page. 3.
ON THE POSSIBILITY TO STUDY THE DATA RECORDINGS CARRIED OUT
IN THE GEODYNAMICS OBSERVATORIES BY A MULTICHANNEL ANALYSIS
D. DELION, DOREL ZUGRAVESCU, ILEANA FATULESCU, V. GHEMIGIAN
Center for Earth Physics and Seismology, Gepartment of Geodynamics, Bucharest
The possibility to use a multichannel analysis to study the geodinamycal
data is analysed for the simple case of the correlation of vertical component
of the gravity field recorded at the Geodynamical Observatory Caldarusani with
theoretical components of the long period, diurnal, semidiurnal and terdiurnal
Earth tides. The result suggests that this method has the possibility to separate
more conveniently, geonomic information from the local perturbating influences
(atmosphere dynamics, local tectonics, temperature, etc.).-
Key words: geodynamics, Earth tides, geodynamical observatory, data analysis,
multichannel system.
LOVE NUMBER VALUES DETERMINED FROM EARTH TIDE RECORDINGS CARRIED OUT IN
THE S. R. OF ROMANIA
DOREL ZUGRAVESCU1, D. DELION1, R. DOROBANTU1, ILEANA FATULESCU1, V. GHEMIGIAN1, N. PUSCASU2
1Center for Earth Physics and Seismology, Department of Geodynamics, Bucharest
2Enterprise of Geological Surveys and Explorations "Oltenia", Craiova
The values of k2 and h2 Love numbers, characterizing Earth deformations under
the influence of a disturbing potential, were calculated for M2 wave from the
Earth tide recordings carried out in the 1980 – 1984 period within the
framework of the geodynamical observatories of the S. R. of Romania. The geodynamical
information contained by these values, respectively, by their time evolution,
will be able to be analyzed, only when the time interval is long enough.
Key words: geodynamics, Earth tide, Love numbers, geodynamic observatory.
THE NEW MAP OF RECENT VERTICAL CRUSTAL MOVEMENTS IN THE S. R. OF ROMANIA – SCALE
1 : 1,000,000
N. M. POPESCU1 and I. DRAGOESCU2
1Center for Earth Physics and Seismology, Bucharest – Magurele
2Institute of Geodesy, Photogrammetry, Cartography and Land Management, Bucharest
The new map of recent vertical crustal movements is a progressive step in
the knowledge of the Earth's crust surface deformation, due to interior factors,
during the last period, in Romania. It is important to take into account that
between the epoch of this map and that of the previous one (edited in 1977)
the great seismic event of March 4, 1977 has occurred. On the other hand, the
geodetic network, used for high precision repeated levelling measurements,
was completed with some new levelling lines. The new map is better correlated
with the tectonic map of S.R. of Romania.
Key words: high precision repeat levelling, recent vertical crustal movements,
levelling line.