**2.4 Magnetic anisotropy**

The magnetic anisotropy transformant, reduced to the pole (**Figure 2B**), shows the boundaries of anomaly-forming objects in contrast. To calculate this transformant, a sliding window size of 5 x 2 km was used.

#### **Figure 2.**

*(A) Module of the horizontal gradient of the geomagnetic field normalized to the pole. (B): Anisotropic transformant of the geomagnetic field normalized to the pole. Black dotted lines indicate major faults. Dashed pink lines indicate tectonic faults identified by the complex of studies performed (gravity exploration, magnetic prospecting, thermal fields, and day surface topography).*

*The Geomagnetic Field Transformants and Their Complexing with Data of Gravitational… DOI: http://dx.doi.org/10.5772/intechopen.111560*

The southern and northern boundaries of the Shakhpakhty tectonic step, in the zone of its junction with the Assakeaudan depression and the Central Ustyurt system of dislocations (up to 0.002 standard units), are characterized by higher-than-usual values of the magnetic anisotropy transformant, which indicates an increase in the degree of heterogeneity of the basement rocks (**Table 1**).

Actually, the Shakhpakhty step is distinguished by reduced values of magnetic anisotropy (0–0.0005 standard units), including the Utezhan, Kozhantai, Northen Kozhantai, Otynshy local structures (**Figure 2B**), which is considered as a favorable historical and geological factor that had an indirect sedimentary section.

#### **2.5 Analytic signal**

Several areas are distinguished according to the nature of the distribution of this transformant.

The areas of local structures Utezhan, Koskudyk, Kozhantai, Northen Kozhantai, and Otynshy are characterized by lower values of the analytical signal, which are isolated in the northern part of the Shakhpakhty tectonic step and in the zone of its junction with the Central Ustyurt dislocation system.

To the southeast of these local structures within the Shakhpakhty tectonic step, but situated in the territory of the Republic of Uzbekistan, Shakhpakhty and Dzhel large gas fields were explored in the Upper Jurassic sediments.

To the south of the Shakhpakhty step, within the Assakeaudan trough, the transformant of the analytical signal exhibits the minimum values at the Kyzgurly, Birinzhik, and Northern Birinzhik local structures.

At the Central Ustyurt system of dislocations (Akmechet structure), increased values of this transformant are observed.

The revealed zonation is quantitatively confirmed by the values of the transformant of the analytical signal. At the Shakhpakhty step, they vary in the range of 0.005–0.008 nT/m, at the Assakeaudan depression they are 0–0.005 nT/m and at the Central Ustyurt system of dislocations they are 0.002–0.02 nT/m (**Table 1**).

A similar nature of the distribution of this transformant, apparently, is associated with: a) the general deepening of the upper edges of the magnetically disturbing masses in a southerly direction; and b) the block structure of the basement, in which magnetically active rocks of various scales are distributed.

#### **2.6 The angle of the geomagnetic field gradient vector—TDR (tilt derivative)**

This transformant (measured in radians) shows the maxima of the initial geomagnetic field regardless of their intensity and makes it possible to trace structural elements and map the position of the studied objects and their contours [4, 5].

The assessment of the depth of the studied objects is determined by the intensity of the TDR maxima (of both signs), which correspond to the axial lines of magnetically active objects. Zero values are their outer boundaries.

The northern part of the Shakhpakhty tectonic step is distinguished by the minimum values of TDR transformant (from 1.567 to 0 radians) normalized to the pole (Utezhan, Koskudyk, Kozhantai, Northen Kozhantai, and Otynshy local structures) (**Table 1**).

Near values of this transformant (0–1.560 rad.) were recorded in the Assakeaudan depression and at the southern part of the Shakhpakhty step (Samtyr, Tabyn, Kyzgurly, Birinzhik, and Birinzhik northern structures).

The maximum negative values (1.200–1.560 rad.) of the dip angles of the TDR transform (Akmechet structure) were found in the Central Ustyurt dislocation system.
