Active fault of Eurasia database (explanatory note)
Principles and methods
2. Principles and methods of creating a database
2.1 Editing database objects
. Objects of the database are active faults and fault zones, as well as active flexures and folds under which a fault is assumed, and zones of deep disturbances, expressed in geophysical fields and manifested on the surface only by indirect signs. The structural expression of the database object is the fault itself and the entire complex of active elements accompanying it, among which a discontinuous or folded component may predominate. The fault line usually corresponds to the most pronounced and emerging to the surface of the discontinuous element of the zone. Separate segments of faults and fault zones can be distinguished as database objects if they are separated from neighboring segments and / or differ from them. Differences can be expressed: a change in the morphology, kinematics or strike of the fault; a change in its severity in the relief, for example, the appearance or disappearance of ledges, hollows and ridges associated with a fault; dividing a single fault into separate branches or adjoining other faults; change in the nature of seismicity. Only such a segment is disseminated by information on active movements obtained during studies within it, and only the epicenters of earthquakes closest to it are correlated with it.
. When editing and evaluating database objects, contextual materials are involved - a set of data that continuously and uniformly covers the entire territory of Eurasia and is reliably tied to the terrain. Based on comparison with contextual materials, the characteristics of each database object are compulsory controlled, which allows us to consider their combination as a single system. The most important of these materials is Toposnov, which is selected as a digital terrain model of 3-sec resolution SRTM V3 (basic toposnov). By comparing with it, all objects are reduced to a single level of image detail and location accuracy. The second element of the kit is a mosaic of color satellite images of LandSat ETM + 15-meter resolution. Based on their interpretation, the location of objects in areas with a poorly divided relief is monitored, the internal structure of fault zones is detailed, and signs of activity of structures and a preliminary assessment of their kinematics are sometimes detected. The kit also includes seismological data borrowed from various catalogs. The results of comparison with them, taking into account the slope of the fault, are used to clarify the position and parameters of database objects as indirect features.
. The interpretation of the database compilation results depends on the scale at which contextual materials are decrypted, objects are edited, and their parameters are evaluated. The working scale at which editing and evaluation of objects is carried out directly in the process of compiling a database is limited by the resolution of the basic topobase. At the same time, it should be generalized enough to provide a high-quality image of the relief model when it is decrypted. As the working editing scale, a scale of 1: 500000 was selected. The scale, in which the database is supposed to be visualized in the form of a map and interpreted by the user (the base scale of the presentation), must provide a high-quality image of objects edited on a working scale. It takes into account the detail of the image that is characteristic of regional maps of active faults as the main source materials for the database and should be more detailed in order to provide the possibility of clarifying the data entered from them. Therefore, the scale of 1: 1,000,000 was chosen as the base demo.
Editing the configuration of objects
. The transfer of lines of objects from source materials differing in their detail to the database is not formal. If the important structural elements on the source materials are not shown in sufficient detail or are displaced relative to the real location, their position and configuration are refined by deciphering the base topography or satellite images, with possible separation into several objects, if the element detects a complex structure or different expression in different parts. If the structural elements in the materials are too detailed, they are generalized with the possible combination of adjacent elements into a single object. All database objects are brought to a view when the intervals between the nodal points of their lines are comparable. The number of points describing the object must be at least four, and the maximum bending angle at the nodal point must not exceed 45º. Thus, all the objects introduced into the database are reduced to a single image detail and standard geometric characteristics.
When decoding the lines of database objects, it is assumed that the active fault is somehow expressed in relief. Regardless of how the structure of the object is expressed on more detailed materials, in the database, lines of objects are drawn according to the decryption elements of the relief (ledges, hollows, ridges) that are distinguishable on the base topography, taking into account the kinematics indicated in the source or assumed from the context. Cases where the fault line remains inconsistent with the relief on a working scale are allowed if it was mapped in this form directly on the ground or in a detailed picture. The condition for including new objects in the database is the consistency of their kinematics with adjacent objects already existing in the database, structural integrity and consistency of the violation system. In nature, simple (without local complications) intersections of active structures are not found. Thus, the intersection of shear zones leads to their curvature and the sequential development of new segments of both zones [Trifonov et al., 1993]. Therefore, the intersection of objects without the presence of these signs, as well as the proximity of parallel multidirectional shifts, are not allowed in the database. Usually, cruciform overlays arise when superimposing objects borrowed from different sources. In these cases, one of them is assigned a lower reliability, and this object at the intersection point is divided and adjusted to obtain a realistic kinematic ratio.
Relationship between private data and generalizations
. Information about the general regional structure is taken into account by including in the database the results of generalized studies, overview maps, and databases reflecting the results of an already conducted interpretation of the primary field information. Parameters resulting from such generalizations are included in the database either in those areas where the properties of existing objects do not contradict them, or if, based on decryption, you can create a new object that matches the generalization, or several objects that differ in the degree of compliance with the properties indicated in the material - source for the zone as a whole.
Different authors interpret the structure differently, and when superimposed in the database, independent materials may partially contradict each other. Nevertheless, the entire body of information is whenever possible fixed and integrated into the general system of database objects. This provides the possibility of different options for its interpretation, which is important for constructing various hypotheses and planning further research. The purpose of compiling the database is to fully and comprehensively present the whole variety of elements of the active violation system. The signs of the key components of this system will naturally appear in the aggregate material of the database as all new local data about specific objects are included in it.
The emerging system of database objects is the result of an analysis of their particular relationships on a local scale. In this case, a local mutual coordination of the properties of the edited and related objects is based on structural and kinematic principles. It is forbidden to evaluate the ratio of objects on the basis of general ideas about the surrounding structure and the possible position of objects in a wide geodynamic context. The regional situation should not be the basis for evaluating data. On the contrary, it is the result of compiling a database and manifests itself with a holistic perception of the material on a more general scale as a form of representing new knowledge.
When the user considers the entire system of database objects on a generalized regional scale, it becomes the basis for further analysis. In this case, the significance of individual objects, determined by the reliability of their activity and speeds of movements, must be taken into account. The value is represented by specific data on a particular object, and the position in the overall structure that it occupies. The database of active faults AFEAD is created to use the characteristics of objects to solve scientific and practical problems, as well as to provide the researcher with a holistic picture of the distribution of active deformations.
Далее: 2.2 Source materials for the Database