مورفوتکتونیک ناحیه دهشیر با استفاده از تکنیک‌های ژئومورفومتری

Introduction
Remote sensing provides fast and economical information to study morphotectonic and structural geology. Morphological and geomorphological analyses of topographic features have useful in structural and tectonic investigations. Some features and models of topography, for example; peaks, strike- ridge geomorphology, passes, plans, channels , pits ,three-dimensional views with imagery drape, cross-sections profile geometry, slope and aspect calculations, shaded relief, curvature maps, rose diagrams of lineations (faults, ridges,…) and structural trend can be extracted from SRTM through systematic digital tectonic geomorphology and digital terrain analysis. These procedures can be fundamental tools in tectonic analyses base on using remotely sensing data. Altogether, bases of this research are structural geology, geomorphology and digital terrain analysis that all extracted from SRTM. There are close communication between fault type and landforms, therefore, we investigated topographic fractures along Dehshir fault and calculated models of topography around it for morphotectonic study.

Materials and methods
We used SRTM to extracted topography features around Dehshir fault. We utilized satellite data include; Landsat, Aster data and geology maps with conjunction fieldwork observations. Digital topography investigation methods for systematic study of tectonic geomorphology features by DEMs along Dehshir fault are constructed respectively; (1) Geometric investigation of features linked to lineations. (2) Feature detection and parameter extraction from DEMs for tectonic geomorphology. In this section, we analyzed; elevation data, numerical differential geometry, digital drainage network and digital geomorphometry. Then, digital image processing of terrain data and spatial analysis of lineaments are done.
This paper describes the morphotectonic of Dehshir area using SRTM. Therefore, to access to the goal of study, analysis of digital drainage network analysis; digital geomorphometry; digital image processing; lineament extraction and analysis; spatial and statistical analysis and digital elevation model-specific digital methods, such as shaded relief models, digital cross-sections, 3D surface modeling and topographic features are extracted from SRTM. Structural information from other sources, such as geological and topography maps, remotely sensed images and field observations were analyzed with geographic information system techniques.

Results and discussion
SRTM analysis of the study area showed a distribution of elevation. Cross-sections across perpendicular of Dehshir fault in NE–SW direction also illustrated fault scarps. Shaded relief images have obviously shown lineaments (e.g.; drainages, channels, fault trace, ridges …). Contour map extracted from SRTM elongated along Dehshir fault and showed fault scarps. Rose diagram of lineaments illustrated morphotectonic pattern NW-SE lanforms of the study area. In classified aspect maps are predominantly NE and SW hillside. Lineaments in the shaded relief, aspect, slope and curvature models showed much information for explanation of morphotectonic.
The results provide an acceptable regional morphotectonic view of the study area. The geomorphology of the study area is dominated by a pattern of sub-parallel mountain ranges and intermountain plains (lowlands, mainly grabens). The study area landforms are strongly influenced by active faults movements (particularly strike-slip faults). The piedmont areas are covered with low slope surfaces (predominantly Holocene alluvium), originating from the mountain channels and spread for kilometers towards the lowlands. The bottom of the medial plains, known as "Kavir" (Persian term for playa), is covered with playa-type mud flats, evaporate (salt) lakes (e.g. Abarkooh, Marvast) and, only locally, by mobile sand dunes (e.g. along Dehshir fault at east of Abarkooh playa).

Conclusion
The results show that digital terrain analysis methods applied on SRTM in the proposed way in this study could extract morphotectonic features from SRTM along Dehshir fault and they contributed to the tectonic interpretation of the study area. According to the evidences extracted from SRTM along Dehshir fault, for example; fault traces, deflected and beheaded drainages, pattern of network drainages, erosion surfaces of uplifted and back erosion of drainages because of the location (situated in quaternary landforms), they are neotectonic evidences for activity of Dehshir fault during quaternary.