Journal of Earth Science, Vol. 26, No. 5, p.712–723, October 2015 ISSN 1674-487X Printed in China DOI: 10.1007/s12583-015-0583-2 Faghih, A., Nourbakhsh, A., Kusky, T. M., 2015. GIS-Based Analysis of Relative Tectonic Activity along the Kazerun Fault Zone, Zagros Mountains, Iran: Insights from Data Mining of Geomorphic Data. Journal of Earth Science, 26(5): 712–723. doi:10.1007/s12583-015-0583-2. http://en.earth-science.net GIS-Based Analysis of Relative Tectonic Activity along the Kazerun Fault Zone, Zagros Mountains, Iran: Insights from Data Mining of Geomorphic Data Ali Faghih 1 , Ahmad Nourbakhsh* 1 , Timothy M. Kusky 2 1. Department of Earth Sciences, College of Sciences, Shiraz University, Shiraz Poste, Iran 2. Three Gorges Research Center for Geo-hazard, Ministry of Education, China University of Geosciences, Wuhan 430074, China ABSTRACT: This paper tests a data mining method for evaluation of the “IRTA” (Index of Relative Tectonic Activity) to investigate the impact of active tectonics on geomorphic processes and landscape development. Based upon K-means clustering of six basin-related geomorphic indices (the hypsome- tric integral, basin asymmetric factor, drainage density, basin shape ratio, mean axial slope of the channel and topographic roughness) that represent the relative strength of active tectonic deformation on topography and morphology, the relative tectonic activity along the Kazerun Fault Zone in the Za- gros Mountains of Iran may be classified into low, moderate and high relative tectonic activity zones. The results allow the identification of the clusters of similarly deformed areas related to relative tec- tonic activity. The utilization of geomorphic parameters as well as IRTA with comparison to the field observations exhibit change in relative tectonic activities mostly corresponding to the change in me- chanism of the prominent fault zones in the study area. KEY WORDS: active tectonics, geomorphic index, K-means clustering, Kazerun Fault Zone, Zagros, Iran. 0 INTRODUCTION Quantifying the geomorphic response of landscapes to ac- tive tectonics is the focus of tectonic geomorphology (Mayer, 1986) as the landscape contains an important archive of the rates and spatial distribution of deformation (Kirby and Whip- ple, 2012). Tectonic geomorphology deals with relations be- tween tectonics and geomorphic processes shaping areas of active Cenozoic deformations (Burbank and Anderson, 2012; Delcaillau et al., 2011, 1998; Molin et al., 2004; Pánek, 2004; Merritts and Vincent, 1989). Therefore, geomorphic investiga- tion in regions of active tectonics is a powerful tool for studies of tectonic geomorphology. The quantitative measurement of landscapes is based on the calculation of geomorphic indices using topographic maps or digital elevation models, aerial pho- tographs or satellite imagery and fieldwork (Keller and Pinter, 2002). Geomorphic indices are a tool for analyzing landforms and evaluating the degree of tectonic activity in a given area (Keller, 1986). Several authors have proposed different tectonic activity classes based on individual geomorphic indices (e.g., El- Hamdouni et al., 2008; Silva et al., 2003; Rockwell et al., 1985; Bull and McFadden, 1977). Some of these classifications have concentrated on specific indices at specific site (e.g., Kusky *Corresponding author: nourbakhsh.ahmad@gmail.com © China University of Geosciences and Springer-Verlag Berlin Heidelberg 2015 Manuscript received August 1, 2014. Manuscript accepted January 6, 2015. et al., 2010; Silva et al., 2003; Rockwell et al., 1985; Bull and McFadden, 1977). Moreover, El-Hamdouni et al. (2008) intro- duced a relative tectonic activity index (IAT) which is an arbi- trary division of geomorphic indices into four different classes based on the summation and average of index values. The aim of this paper is to test a data mining technique of geomorphic indices to produce a single index that can be used to character- ize relative active tectonics away from personal judgments. For this purpose, one of the data mining methods known as “K- means clustering” has been used for dividing geomorphic index values into homogeneous clusters followed by a discussion of the active tectonics based upon field-based structural and geo- morphic observation. In this work, we have studied the tectonic geomorphology of 76 sub-basins along Kazerun Fault Zone (KFZ) in the Zagros Mountains of Iran (Fig. 1) to characterize the relative tectonic activity using quantitative analyses of the geomorphic indices. 1 GEOLOGICAL SETTING The Zagros fold-thrust belt (Koyi, 1988) in the Alpine- Himalayan Orogenic System formed as a result of closure of the Neo-Tethys ocean during oblique convergence and ongoing collision (Allen and Armstrong, 2008; Authemayou et al., 2005; Alavi, 2004, 1994; Allen et al., 2004; Tatar et al., 2004; Ver- nant et al., 2004; Talebian and Jackson, 2002) between the Afro-Arabian and Central-Iranian plates (Alavi, 1994, 1980; Berberian and King, 1981; Ricou et al., 1977; Haynes and McQuillan, 1974; Stöcklin, 1974; Takin, 1972). The NW- trending Zagros Fold-Thrust Belt extends for more than 1 800 km from eastern Turkey to the Strait of Hormuz in