S. Rajabi; M. Eliassi; A. Saidi; A. Shahidi
Abstract
In this research, heterogeneous fault slip data are used as the main data for doing paleostress analysis in North-Tehran tectonic wedge, which is restricted between Mosha and North-Tehran faults. Using these data and paleostress methods, the studied area is divided into 15 smaller stable stress regions ...
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In this research, heterogeneous fault slip data are used as the main data for doing paleostress analysis in North-Tehran tectonic wedge, which is restricted between Mosha and North-Tehran faults. Using these data and paleostress methods, the studied area is divided into 15 smaller stable stress regions and the mean stress tensor related to each region is determined. Then, stress events are separated using Multiple Inverse Method. Based on mean stress tensors -obtained from stress regions- and rotation of fault data orientation -based on Anderson’s theory in compressional tectonic regimes-, the stress trajectory map is sketched for mean stress tensors acting in the regions during geological time. Configurations of trajectories show that they seem to obey the overall tectonic regime in Iran. This result refutes that the North-Tehran tectonic wedge could be a dynamic wedge.
M. R. Moshrefi far; A. Alavi; M. Mohajjel
Abstract
In this research, separation of paleostress phases in the central part of Dehshir fault is investigated based on the study of heterogeneous fault-slip data and their related slickenside lineations. These data are measured from the Certaceous (Taft limestone), ...
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In this research, separation of paleostress phases in the central part of Dehshir fault is investigated based on the study of heterogeneous fault-slip data and their related slickenside lineations. These data are measured from the Certaceous (Taft limestone), early Eocene (Kerman conglomerate) and Eocene (Volcanics) formations. The main criteria used here to identify sense of fault-slip are stratiographic separation, accretionary mineral steps, Riedel shears and tension gash. The existing faults in the region of investigated often show two NE and NW trend in which the latter is usually dominant. Based on the study of heterogeneous fault-slip data and their related slickenside lineations and using the multiple inverse method, at least two phases are expected. These phases show that the axis of maximum principal stress, σ1, is at NE trend and that of minimum principal stress,σ3, is at NW trend. The location of σ3 usually indicates that the strike-slip and reverse strike-slip faults mostly occur in the region. In addition, the shape of the stress ellipsoid is prolate in the region.
M. Eliassi; S. Ahmadian
Abstract
Analysis of paleostress history in Kan_Karaj Area is the main object of this research. Paleostress phases were determined and categorized by numerous mesoscale faults containing slickenside lineations .The results were controlled and supported by some other geological features such as orientation of ...
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Analysis of paleostress history in Kan_Karaj Area is the main object of this research. Paleostress phases were determined and categorized by numerous mesoscale faults containing slickenside lineations .The results were controlled and supported by some other geological features such as orientation of axial plane of folds, intrusion and stylolitic planes. The orientation of finite principal stress axes and geometrical shape of stress ellipsoid in a 4-D stress space were analyzed by determination of rotational axis of each sub-area, according to Anderson Theory. Two different stress phases were separated and geometrical configuration of the maximum compressional stress trajectory were illustrating on the structural map. The resulting trajectory shows north- south trend with an outstanding convergence to the north which reflects incremental intensity of stress in that direction during the fault system activities.