Determination of transverse structures based on lineament analysis: a case study of the Fergana valley

Abstract

As a result of the stress state of the lithospheric block, a structure of orthogonal cracks may appear as a network of straight or arcuate topographic elements of the regional extent on the Earth’s surface—lineaments. In the last decade, one of the directions of lineament analysis had been the identification of the so-called transverse structures using remote sensing methods, which often serve as the geological boundaries of crustal blocks. Various lineament analysis methods are being actively developed: image enhancement, manual digitizing methods, and automatic extraction using software and algorithms. Revealing the relationship between lineaments and their characteristics with natural and anthropogenic processes is the relevant task. The tectonic lineament network is associated with deep faults and, in particular, ore regions that can be localized at the intersection of large lineaments. Therefore, most studies of increased accumulation of lineaments are carried out in areas where mineral deposits and groundwater deposits are identified. These areas include the Fergana region, which is one of the five oil and gas regions of the Republic of Uzbekistan. The presence of a fund of promising traps justifies the need for comprehensive geoinformation support, including satellite methods, and the possibility of transition to automatic methods for analyzing tectonic processes. Therefore, in this study, an automated lineament analysis was carried out in order to identify and interpret the transverse structures in this region. The study period (May–November 2019) was chosen to take into account the intensive exploration work in the region and the technical parameters of the images (without clouds). Landsat 8 satellite images were processed by the automated method of lineament structures interpretation in the LEFA program in the MATLAB environment. During the visual analysis of the processed images, it was identified that there was a temporary change in the number of lineament structures by month. At the same time, the northwestern part of the region (Namangan region) is characterized as the zone of the strongest manifestation of lineament structures. Further detailing of the lineament structures in terms of direction and orientation made it possible to determine the transverse structures. Thematic maps with the geospatial location of transverse structures showed that the nature and clarity of transverse structures varied depending on the features of the geological structure of the sections they intersected.