Ph.D. Theses

Structural analysis of contemporary horizontal velocities and strains of the Earth’s crust of the territory of Azerbaijan

Applicant: Elnara Vagif Ahmadova

Speciality: 2507.01 - Geophysics, methods of geophysical exploration of minerals

Field of science: Earth sciences

Relevance and processing degree of the topic:
The contemporary geodynamic state of the territory of Azerbaijan is determined by the interaction of Arabian and Eurasian plates within the framework of plate tectonics. Space geodesy GPS (Global Positioning System) method is a modern method used in the world to study the interaction of plates and the strains resulting from this and to track horizontal movements in the lithosphere (J.T.Freymueller, T.A.Herring, Ch.Reigber, R.E.Reilinger, Floyd M., Vernant Ph., S.McClusky, F.Kadirov, R.King, A.Barka and others). Over the past 25 years, the application of space geodesy GPS method has created opportunities to measure the contemporary movement velocities of lithosphere plates and the strains at the contact boundaries of plates with high accuracy, at the same time to verify a large number of hypotheses about plate interactions. Contemporary GPS velocity data not only allows the verification of many theoretical tectonic considerations, but also contributes to the investigation of the main point of the strains that occur during the contemporary development of the Earth’s crust.

The study of the regularities of dislocations and strains happened in the Earth’s crust within the plates is of great importance in clarifying the nature of geological processes (earthquakes, eruption of mud volcanoes, landslides, etc.) and is one of the topical issues of geophysics. One of the topical issues that need to be clarified from this point of view is the identification of different geodynamic areas in the structure of spatial distribution of GPS horizontal velocities of the lithosphere in the territory of Azerbaijan, which forms the eastern part of the Caucasus block, modeling the interaction of blocks and identifying small plate interior areas (“domains”). Besides GPS measurements, other field data is also used to solve the problem.

Research aims and objectives:
The aim of the dissertation is to conduct a structural analysis of the spatial distribution of contemporary horizontal velocities of the Earth’s surface obtained from new measurement data in the Azerbaijan GPS network, to identify the small plate interior domains, which are distinguished by their individual kinematic features and to research the correlation of the area by its tectonic elements, gravitational anomalies and seismicity.
The following issues have been solved to achieve the aims:
  • Conducting periodic measurements, collection and processing of database at the Azerbaijan GPS polygon;
  • Calculation of the velocity field of GPS contemporary horizontal movements of Azerbaijan and neighboring areas (2000-2017), preparation of distribution maps of GPS velocity vectors, its Northern (VN) and Eastern (VE) components;
  • Identification of areas with different geodynamic regimes and theoretical calculation of horizontal velocities for GPS points, which are located here, based on the model of block interaction;
  • Creating digital 3D geological model of the Earth’s surface, basalt and Mokhorovichich borders in the Caucasus region (Azerbaijan) with GOCAD and Abaqus software;
  • Compilation of a map of stress distribution in Azerbaijan and neighboring areas according to the mechanisms of earthquake focuses with magnitude Mw ≥5 during 1990-2017 using the CASMO method (World Stress Map);
  • Structural analysis of GPS velocity distribution in the territory of Azerbaijan, identification of domains with different GPS velocity and geophysical field characteristics and their comparative analysis with tectonic structures;
  • Construction of distance dependence graphs of VN and VE components of GPS velocity vectors on selected profiles and study of kinematics of defined domains;
  • Correlation of domains, which are distinguished by different characteristics, in the GPS velocity field with local gravitational anomalies and their geological interpretation.

Research methods:
The following research methods were used in the dissertation:
  • The method of Space geodesy (GPS) was used to study con-temporary movements in the Earth’s crust;
  • The data obtained by GPS method was processed by GAMIT/GLOBK software package developed by Massachusetts Ins-titute of Technology;
  • TDEFNODE – Fortran program for modeling the rotation of elastic lithosphere blocks;
  • Stress and strain state of the Caucasus region (Azerbaijan) was investigated by using Abaqus TM and “World Stress Map” programs;
  • The distribution map of the earthquake counts was compiled by the sliding window technique;
  • Generic Mapping Tools (GMT) and SURFER programs were used to compile the maps.

The key points of the defense:
  1. Movement of the Lower Kura, Gobustan and Absheron structural areas in the direction of NE in accordance with the kinematics of the South Caspian block under the influence of the Iranian plate
  2. Plate interior “domains”, which are separated by a complex approach, in a new field of discrete GPS velocity and their correlation with the area of local gravitational anomalies in the territory of Azerbaijan based on the data of 2000-2017.

Scientific innovation of the research:
The following scientific innovations were obtained by a comprehensive comparative study of stress and gravitational anomalies using GPS measurement and seismic monitoring data in Azerbaijan and neighboring areas, topographies of the Earth’s surface, Mokhorovich and Basalt geological surfaces and mechanisms of earthquake focuses:
  1. Taking into account the new GPS measuring points of Azerbaijan, which is the eastern part of the Caucasus block, the parameters of contemporary horizontal movements were determined on the basis of the monitoring results of 2000-2017.
  2. It was determined that Lower Kura, Gobustan and Absheron structural zones in the east of the Western Caspian fault are moving clockwise together with the South Caspian block under the influence of the Iranian plate.
  3. A map of the distribution of the earthquakes counts for Azerbaijan and neighboring areas was compiled and it was determined that the maximum value of GPS velocity vectors belongs to the areas where both the direction and the value change.
  4. It was noted that the direction of the horizontal stress vector (σ max) calculated by the CASMO (World Stress Map) method in the territory of Azerbaijan is mainly in the direction of contemporary movement of the Earth’s crust and there is a difference in some places and it is assumed that besides collision tectonics, local sources of stress also played a certain role in the formation of stress.
  5. “Domains” that behave as plate interior block and are important in clarifying the nature of tectonic processes (earthquakes, eruption of mud volcanoes, landslides, etc.) have been identified in the field of GPS velocity and contemporary strain in the territory of Azerbaijan.
  6. It was determined that there is a correlation between the area of local gravitational anomalies and the spatial distribution of domains in the territory of Azerbaijan, which indicates that these domains are related to the structural forms of the Earth’s crust and the composition of rocks.
  7. The sharp change of the direction of the velocity vector at the Yevlakh (YEVL) GPS point relative to the surrounding points is due to the nature of the Yevlakh-Agjabadi large negative local gravitational anomaly, especially volcanic occurrences in the geological structure of the depression in the Middle Kura “domain”.

Theoretical and practical significance of the research:
The obtained research results and GPS measurement data can be used to determine the kinematics of lithosphere plates, as a rule, to discover and clarify the boundaries of the plate, where strong earthquake focuses are located; to identify major fault systems and relatively more seismic hazard zones; to monitor changes of stress and strain state of the environmental and the accumulation of elastic strain in this type of fracture zones.

The developed GPS velocities, the database of their processing and analysis results can be attached to the regional archive and used for applied research in the territory of the Republic of Azerbaijan, including for solving engineering seismological issues.

The obtained results can be useful in a research such as the assessment of endogenous processes and a study of the strain mechanisms of the Earth’s crust. Especially, since the horizontal movements of the Earth’s crust influence the processes in the mantle, the study of this interaction is a database for studying the contemporary evolution of the Earth’s crust. The obtained results are important for evaluating interpretation in solution of the various raised issues.

So, the obtained structural and kinematic schemes can be useful in the creating seismotectonic models, as well as in the specifying con-temporary seismic hazard maps.

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