Ph.D. Theses


A gravity model of the deep structure of the Earths crust and geodynamic peculiarities of the South – Eastern Caucasus

Applicant: Gunel Rafael Sadigova

Speciality: 2507.01 - Geophysics, geophysical methods of minerals exploring

Field of science: Earth sciences


Relevance and state of knowledge of the topic

Gravity anomalies and their transformations play an important role in the study of the geological structure of the Earths crust, and their analysis with the results obtained from other geophysical methods (seismic, electrical, magnetic, etc.) allows us to obtain fundamentally new information about the geological and tectonic structure.

Beginning at the end of the 20th century, digital methods were rapidly applied to the interpretation of geopotential areas. In this area can be noted V.I.Aronov, E.Q.Bulakh, R.J.Blakely, R.W.Simpson, F.A.Kadirov, A.K.Malovichko, T.S.Amiraslanov, S.A.Serkerov, V.A.Gadirov, V.O.Mixaylov, V.I.Starostenko, İ.E.Stepanova, V.N.Straxov, A.V.Tsirulskiy, S.A.Tikhotskiy and the work of other scientists.

Over the last decade, the mathematical theory of the interpretation of gravity anomalies has developed significantly. Currently, the digital analysis of gravity field data is considered a new direction in the theory of the interpretation of potential fields. The development and application of gravity field transformation methods to determine the density boundaries in the geological structure of any area are very relevant. The development and practical application of new algorithms for the calculation of gravity field transformations expands the possibilities of analysis in solving geological problems.

The issues of digital modelling of gravity field data of the South-East Caucasus (PreCaspian-Guba zone) are considered in the dissertation. The territory of Azerbaijan is located in the zone of active interaction between the Arabian and Eurasian plates (Mckenzie, 1972, Philip et al., 1989). The interaction between these plates began 10-30 million years ago and continues to this day (Robertson, 2000; Allen et al., 2004). The long-term interaction of plates determines the geodynamic conditions of the area and plays an important role in forming density boundaries in the Earths geological structure. Taking this into account, the obtained digital gravity models in the South-East Caucasus are interpreted in a complex way together with the parameters characterizing the geodynamic conditions of the research area (seismic, horizontal and vertical velocities, strain and deformations).

In the dissertation, the geodynamic conditions and kinematic properties are studied using the results, obtained by the method of space geodesy, GPS (Global Positioning System) and compared with gravity models. At the same time, the results of measurements conducted with the new ZLS BURRIS gravimetry and modern geodetic instruments (GPS Trimble 5700, Level
Pentax-AFL320, LEICA total station TS06), available at the institute allowed us to obtain new information and make new interpretations of the gravity field and modern movements in the selected Samur-Baku profile.

It should be noted that the correlation between the digital gravimetric models of the depth structure in the area and the new kinematic parameters characterizing the geodynamic conditions has not been sufficiently studied to date. The study of this problem is of great scientific and practical importance, and the results of the complex analysis conducted in the research area can be used to study the geodynamic hazard for infrastructure in the region (Baku-Novorossiysk oil pipeline, Takhtakorpu reservoir and Shollar water pipeline, etc.) and the detection of oil and gas structures.

Purpose and objectives of the research
Digital modelling of Bouguer gravity field data of the South-East Caucasus and study of the correlation of the obtained results with the parameters characterizing the geodynamic conditions of the area.
In this regard, several main issues have been resolved:
  • Determination of the power spectrum and density boundaries of the gravity field of the research area;
  • Development and application of a program for calculation of local anomalies of the gravity field;
  • Construction of a 3D digital gravity model of the sedimentary layer;
  • Conduction gravity field measurements in the Samur-Baku profile, construction of a 2D gravity model of the depth structure;
  • GPS data is used to calculate the strain caused by horizontal movements on the Earths surface;
  • Investigation of regularities between digital gravity models of the research area and the parameters characterizing the geodynamic conditions.

Research methods:
In the dissertation, the following research methods were used:
  • The Hartley transform was used to calculate the power spectrum and local anomalies of the research area Bouguer gravity field;
  • The Spector-Grant method was applied to determine the average depth values of the main density boundaries in the depth structure;
  • The Butterworth filter was used to calculate low-pass and high-pass gravity anomalies;
  • The 3D digital gravity model of the sedimentary layer was constructed by the GR3DSTR program;
  • E.Q.Bulakhs matching method was used to construct a 2D gravity model of the Earths crust depth structure in the Samur-Baku profile.

Main defending statements:
  • 3D digital gravity models of the research area depth structure;
  • Regularities between digital gravity models of depth structure and parameters characterizing geodynamic conditions.

Scientific novelty of the research:
  • The average depth of the density boundaries (16.6 km and 1.8 km) of the research area, which causes intensive anomalies in the Earths crust, was determined;
  • Low-pass and high-pass gravity anomalies were calculated using the cut-off wavenumber of the power spectrum;
  • A computer program was developed to calculate local anomalies in the gravity field;
  • The correspondence of the Bouguer gravity field local anomalies to oil and gas structures was determined;
  • The sedimentary layer depth 3D digital gravity model was constructed using a quadratic density function. The maximum depth was determined in the Guzdek and Maraza regions (11 km) and the minimum depth in the Gonagkend, Gilazi, Garabulag, Dubrar regions (4 km);
  • A 2D gravity model of the Samur-Baku geologicalgeophysical profile depth structure was constructed and the MOHO boundary was clarified;
  • Comparison of the sedimentary layer gravity model and the velocity model at a depth of 5 km has determined the presence of small seismic wave velocities in the deep part and high seismic wave velocities at low depths of the sedimentary layer;
  • Comparison of the gravity field regional anomalies and the velocity model at a depth of 15 km showed a decrease in seismic wave velocity in the zone of regional minimums and an increase in the velocity in the transition zone of anomalies;
  • The minimum deformation velocity was observed in the zone of regional anomalies and the deformation velocity increased in the transition zone of anomalies.

Theoretical and practical significance of the research:
The methodology developed in the dissertation is of theoretical importance and can be applied in other regions. The results of the complex analysis of the South-East Caucasus are of great practical importance in the study of geodynamic hazards for the infrastructure located in the region (Baku-Novorossiysk oil pipeline, Takhtakorpu reservoir and Shollar water pipeline, etc.). At the same time, the sedimentary layer depth gravity model and local gravity anomalies are of practical importance in oil and gas exploration and well location selection.


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