Description of the Active Faults of Eurasia Database
Principles and methods
2.2. Source materials for the database
. When compiling the database, it is important to fill uniformly with information about the manifestations of active tectonics of the entire area of the database cover without a priori dividing it into highly active and stable territories, although active structures are rare and not reliable in the latter. The initial descriptions of active structures, maps and databases of different regions differ in the amount of information displayed in them, may not overlap and even contradict each other, especially if they were created at different times and by different methods. In some places this creates a false impression of the differences in the geodynamic situation and the degree of activity. The database includes all information related to active tectonics, takes into account all representations and models that are justified. In this case, the task is to level these differences based on uniform criteria for assessing activity parameters.
Expert opinions as a type of information
. The specificity of geological research is that the established facts (for example, field measurements of fault characteristics) are the result of subjective assessments, which often differ among different observers of the same phenomenon. The proven facts are often the expert opinions of researchers. This introduces a share of conventionality in the division of information into objective data and subjective opinions, based, in turn, on their own primary data or a synthesis of other people's interpretations. A correctly published independent opinion of a competent researcher is the result of additional processing and understanding of the whole complex of evidence. Therefore, when compiling the database, in addition to the information stated in the source materials as actual data, expert conclusions are often used to justify the properties of objects, often presented in the form of maps.
The proportion of expert assessments and secondary interpretations in the aggregate of justifications is obviously lower than that of the primary data, and the significance of such opinions depends on the qualifications and scientific authority of the experts, on the degree of consistency of their assessments. All things being equal, greater importance is assigned to more recent publications. When expert opinions are included in the database, compilers evaluate their validity by deciphering the contextual materials and how they fit into the existing data set. Compilers of the database do not rethink expert conclusions based on generalizing models. As data accumulate, the influence of subjective factors on the assessment of various active faults and zones is leveled. The database is the author's in relation to the assessment of the properties of individual objects and, at the same time, a way of integrating and summarizing the data and opinions of different researchers. This makes it possible to reveal the general properties of the system of active deformations, despite the diversity and heterogeneity of its particular elements.
Accounting for the latest tectonics
. Displacement along active faults, as a rule, is a continuation of the Early-Middle Pleistocene, Pliocene, and, in general, the latest movements and inherit their main parameters. In this regard, it is justifiable to use materials when compiling the database not only according to the actually active, but also according to the latest tectonics. In compiling the database, only faults that are active in the second stage of the neotectonic stage and mountain formation, which in some regions covers the Pliocene quarter (sometimes also the end of the Miocene), and in others only the quarter, and during which there were no fundamental structural changes, are taken into account, plan. Only the internal structure of the fault zones could be changed while maintaining the general direction of motion.
The task of the compilers of the database is to analyze neotectonic materials and evaluate their elements for compliance with the criteria for the allocation of active structures. As a rule, these materials are represented by various maps, diagrams and databases, the content of which is determined only by the legend and does not provide a justification of the characteristics of individual structures. Interpretation of their age is the expert opinion of the author of the material, and faults, designated by some researchers as the latest, others are often classified as active.
Among the newest faults, three categories stand out. The first is represented by active faults that inherited during the quarter or Pliocene-quarter. Taking into account the late Pleistocene displacements along them allows us to clarify the structural-kinematic parameters, displacement velocities and, ultimately, the significance of such active faults. The second category includes the latest faults that are present on neotectonic maps and, when deciphering detailed distance materials and analyzing seismicity, show signs of movements in the Late Pleistocene - Holocene. Such newest faults are included in the database with one or another certainty of activity. Finally, the third category consists of Pliocene-Quaternary or Quaternary faults, along which late Quaternary movements have not yet been identified, but an analysis of contextual materials suggests that they can be detected, at least fragmentarily, with further research. They are included in the database with minimal reliability of activity, since their parameters specify the general structural and dynamic situation in the region, and some active faults are structurally or dynamically related to them. Their inclusion in the database helps to plan further study of the latest structures in order to determine their activity.
These circumstances make it necessary to more differentiate the active structures according to their reliability. For each object, the entire totality of information and expert opinions and its position in relation to adjacent objects are analyzed. Based on such an analysis, its reliability is evaluated. In highly active areas saturated with active faults, greater rigor of justification is required when neotectonic elements with weakly expressed signs of activity are introduced near them. In weakly active areas, where there are almost no reliably active faults, more elements that show similarities with active structures in context materials can be entered into the database with a minimum certainty from a neotectonic map. When comparing violations with different ages of recent movements, the degree of generalization of their structural elements is important. When detailing the material, the severity of the inheritance of active disturbances from the latest decreases, since changes in the internal structure of fault zones can occur over time. Starting from a certain degree of generalization, the arrangement of elements of active tectonics more and more corresponds to the structural plan of disturbances active at the previous stages of the Pliocene-Quaternary development. With this in mind, the scale of editing the database was chosen sufficiently generalized to consider active violations as inherited from the latest structure and use neotectonic maps to search for manifestations of active tectonics.
Integration of heterogeneous information
. Different researchers, based on their data and ideas, offer different versions of maps depicting features of active tectonics of the same territory. All materials are integrated into the database as they become available, without first selecting conditionally correct ones. At the same time, the selection of specific information for inclusion in the database is limited to individual structural elements, and the entire system of objects is improved by accumulating data reflecting various information and opinions. This is done by indicating the authorship of each piece of information about the object and re-evaluating its attributes depending on the coincidence or contradiction of the opinions of different authors.
If the new data does not correspond to the information already available in the database, then attention is drawn to the degree of their validity. With a comparable level of factual justification, a relatively greater reliability is assigned to more modern concepts. When comparing studies with close publication dates, higher validity is determined by: topographic detail of the study; saturation with specific information; perfection of methods and technologies; scientific reputation of the authors; clarity of the statement of the result and its cartographic presentation. As new data become available, the assessment of the reliability of the object and determination of its parameters change. It is possible to delete an object if it was poorly justified, and new reliable data contradict its existence. The basic principle is to change the former to reflect the new, not to reject the former, but to supplement it. This approach reflects the history of the study of the territory and ensures its continuity. If, with the advent of new data, a glut occurs, which interferes with perception on a basic scale, then a fragmented thinning of the system of objects is performed. Unreliable fragments are removed.
Thus, the development of the database is a sequential process of clarifying ideas about active tectonics, ensuring the continuity and integration of the results of various researchers. The application of this technique leads to an increase in the informational value and analytical potential of the database as a source material for case studies and is intended to show the diversity of modern tectogenesis and to contribute to the formulation of tasks for further work.
The compilers of the database of active faults AFEAD saw their task in considering each fragment of the material on a working scale to supplement the data and estimates previously included in the DB-96 with new information and expert opinions; specify and correct the location and detailed shape of objects; to evaluate the attribute values of new faults, taking into account the properties of the system of objects already established in the considered section, and, if justified, to change the attribute values of old objects using new data.
Далее: 3. Description of database object properties