Structural Traces of Secondary Faults(Fractures) along the Main Faults and Their Reliability as Kinematic Indicators

Secondary/minor structures occurring along the main fault surfaces are important indicators for judging the kinematic characteristics of faults.However,many factors can lead to the formation of these structures,which results in the difficulty for rapid judgment and application in the fields.A series of secondary faults/fractures developed due to the movement of main faults are the most important and widespread phenomena in the scope of brittle deformation.The morphology of the main fault surfaces is various,and former researchers mainly discussed the structures on the main even fault surfaces. However,the fluctuation of fault surfaces is the intrinsic character of the faults,and the intersection between the main fault and secondary faults/fractures can produce a series of kinematic indicators on the main fault surfaces.Based on previous studies and our observations,i.e.the structural traces of the P,R,R',T and X shears/faults along the main faults,some indicators which are rarely reported previously,are described in the paper.Furthermore,their reliabilities are also discussed,and more practical and reliable criteria are brought forward.We suggest that the simple application of congruous and incongruous steps without knowing their exact origins should be abandoned in the fields,and several types of indicators along one fault surface should be checked with each other as much as possible.Meanwhile,the origins of some other arcuate indicators on the fault surfaces are also discussed,and new models are brought forward.

Folded Radiolarite Unit as a Kinematic Indicator of the Zagros Collision Processes, Southwestern Iran

Radiolarites have an important role in the reconstruction of the paleogeography, bathymetry and their coexistence with ophiolites gives an opportunity to determine the tectonic his- tory of collisional zones. The radiolarite units of the southwestern Neyriz are part of the Zagros ac- cretionary prism and positioned beneath the thick bedded carbonate sediments of Tarbur Forma- tion. The existing various structural elements within this unit give a unique fortunate for investiga- tion on the deformation history and studying of the kinematics of the Zagros collision zone. The nu- merous evidence show that this unit has experienced different deformation conditions during ongo- ing evolution, including ductile, brittle-ductile and brittle deformation conditions. The main strike of E-W for axial planes of folds, eastward trend and plunge of fold axes, boudins＇ neck axes and Type III of the fold interference patterns are indicators of formation and evolution of folds during tran- spressional deformation. Structural evolution of the study area has been affected by an NE-dipping subduction zone of Neo-Tethyan oceanic lithosphere below the Iranian microcontinents. These structural elements suggest that high mechanical anisotropy and two successive generations of fold- ing simultaneously with thrusting and extrusion of this unit had led to formation and evolution of this highly asymmetrical folded unit on top of the subducted oceanic crust.

Dark halos acting as chaos controllers in asymmetric triaxial galaxy models

We study the regular or chaotic character of orbits in a 3D dynamical model,describing a triaxial galaxy surrounded by a spherical dark halo component.Our numerical experiments suggest that the percentage of chaotic orbits decreases exponentially as the mass of the dark halo increases.A linear increase of the percentage of the chaotic orbits was observed as the scale length of the halo component increases. In order to distinguish between regular and chaotic motion,we chose to use the total angular momentum Ltot of the 3D orbits as a new indicator.Comparison with other,previously used,dynamical indicators,such as the Lyapunov Characteristic Exponent or the P（f） spectral method,shows that the Ltot indicator gives very fast and reliable results for characterizing the nature of orbits in galactic dynamical models.