The Saymareh River (with near to 400 km length) has been originated from the Zagros Mountains by combination of Gamasayab, Gharasu and Kashkan rivers and finally flows into the Hour-Al-Azim wetland on the Iran and Iraq border zone. The final segment of this river (with near to 200 km length) is called Karkheh River and totally, it is the third long river (about 755 km) in Iran. The structures of the Zagros Mountains on the northeast margin of the Arabian plate reflect quaternary tectonics of this region. We have used a quantitative method to assessment of quaternary tectonics in the Saymareh-Karkheh river basin. In this paper, for the first time six geomorphic indices: hypsometric integral (Hi), the stream length-gradient (SL), asymmetry factor (Af), mountain-front sinuosity (Smf), valley floor width-valley height ratio (Vf) and basin shape (Bs) have analysed for comparison of different landforms  . Then, mean of above index or Iat has calculated for determination of relative active tectonics levels. Previously, this approach has been done in the USA by  , Spain by  .
2. Geologic Setting
The Saymareh-Karkheh river basin is located on the Zagros Mountain that is an orogenic belt in the southwest Iran. This mountain has formed due to convergent regime between the Arabian and Eurasian plates during Cenozoic. The Saymareh-Karkheh river basin (51,341 km2) is located on the Zagros  . The Zagros is underlain by Phanerozoic sedimentary sequences which it has been formed hundreds anticlines and synclines (Figure 1).
The anticlines and synclines have got NW-SE dominant striking in the study area. The folding intensity has decreased toward the southwest. The earthquakes in the study area have got high frequency and small to moderate magnitude, thus seismic analysis of active tectonics is difficult.
The main fault zones of the Saymareh-Karkheh river basin are Kabirkoh, Khoramabad, Kerend and Sahneh faults. The rock resistances have categorized based on rock types as: low (alluvial deposits, marl and conglomerate), moderate (gypsum, dolomitic limestone and gypsums marl), and high (limestone and sandstone) based on  . Figure 2 and Figure 3 show lithology and their
Figure 1. Location of the study area (Google Earth 2016).
Figure 2. Geological map of the study area.
Figure 3. Distribution of rock strength levels.
3. Geomorphic Analysis
Geomorphic indices are useful for quaternary tectonic investigation. We have measured six geomorphic indices mountain-front sinuosity (J), the stream- length gradient (SL), asymmetry factor (Af), hypsometric integral (Hi), basin shape (Bs), and valley floor width-valley height ratio (Vf). These indices have obtained for the Saymareh-Karkheh river basins, that flowing to the south- westward. This basin has divided into 35 sub-basins (Figure 4).
3.1. Stream-Length Gradient
Firstly, the stream-length gradient index has defined by  and it was used for many researchers such as  .
To measure the values of this index, the drainage network and topographic maps are necessary. The contours distances are selected 20 meters.
The stream-length gradient index has calculated along all of sub-basins using a DEM based on topographic maps (for example sub-basin no.27 in Figure 5). Based on  , the results are shown in Table 1 and Figure 6.
3.2. Asymmetric Factor
Firstly, the asymmetric factor (Af) has defined by  . The asymmetric factor varies from 19.8 (sub-basin no. 23) to 86.8 (sub-basin no. 4) in the study area and results are shown in Table 1 and Figure 6.
3.3. Hypsometric Integral
Firstly, the hypsometric integral (Hi) has defined by  . This index that shows
Figure 4. Thirty five sub-basins of the Saymareh-Karkheh river basin.
Figure 5. Longitudinal river profiles and measured SL values for three basins in the study area.
3.4. Valley Floor Width to Valley Height Ratio
Firstly, Valley floor width to valley height ratio (Vf) has defined by  . For measurement of this index, a distance varying from 2 km were set and the values
Table 1. Values of geomorphic indices.
Figure 6. Distribution of six index and classification of them into three classes.
Figure 7. Hypsometry curves of two sub-basins (no. 19, 27).
3.5. Basin Shape
Firstly, the basin shape index (Bs) has defined by  . This index has calculated by using the topographic maps and the results are shown in Figure 6 and Table 1. The basin shape index ranges from 1.12 (sub-basin no. 24) to 4.46 (sub-basin no. 2).
3.6. Mountain Front Sinuosity
Firstly, the mountain front sinuosity index (J) has defined by  . We were measured the mountain front sinuosity index for 23 mountain fronts (Figure 6
Figure 8. Location of sections for Smf and Vf calculations.
4. Results and Discussion
Based on previous work on the salt and mud diapirism  -  and neotectonic regime in Iran  -  , Zagros in south Iran is the most active zone  -  . Then, Alborz  -  and Central Iran  -  have been situated in the next orders. Thus, the study area has been affected by an important regional shortening, but this research tried to evaluate levels of relative tectonic activities in a wider region by using of six geomorphic indices. The averages of these indices have used to investigation in the Saymareh-Karkheh river basin. The values have divided into very high, high, moderate and low levels and their distribution are shown in Table 1 (IAT column) and Figure 9.
Figure 9 shows the result of the classification for each basin; 23.7% (12,180 km2) to Class 2; 62.9% (32,318 km2) to Class 3; and 13.3% (6843 km2) to Class 4.
The Sahneh fault zone is the most important part, based on Iat and connects the Morvarid fault in the NW to the Nahavand fault in the SE. Tectonically, the mechanism of the Sahneh fault is high angle reverse with dextral strike slip component, and is compatible with the earthquakes focal mechanism solution, movement of the Arabian plate.
Figure 9. Distribution of Iat classes.
The Saymareh-Karkheh river basin in the southwest Iran was selected for investigation of above quantitative method. Six geomorphic indices have measured in the Saymareh-Karkheh river basin. Finally, index of active tectonics was measured by combination of the below geomorphic indices; valley floor width-valley height ratio, mountain-front sinuosity, stream-length gradient, hypsometric integral, drainage basin asymmetry factor and basin shape.
The high values of Iat were found along longitudinal fault of Zagros Mountain such as Sahneh fault zone. The most parts have got moderate levels of active tectonics, because they have shown class 3. Also, the low values of Iat have located on plains and un-faulted areas.
This work has been funded by department of geology, Islamic Azad University, Science and Research branch, Tehran, Iran. Also, special thanks to vice-presi- dent for research in Science and Research branch, Tehran.
 Abdideh, M., Qorashi, M., Rangzan, K. and Arian, M. (2011) Assessment of Relative Active Tectonics Using Morphometric Analysis, Case Study of Dez River (Southwestern, Iran). Geosciences, 20, 33-46.
 Abdolizadeh, S., Maleki, Z. and Arian, M. (2016) Earthquake Hazard Zonation and Seismotectonics of the Bandar Abbas Area, Zagros, Iran. Open Journal of Geology, 6, 210-224.
 Alizadeh, H. and Arian, M. (2015) Rule of Structural Factors in Formation of Porphyry Copper Deposits in South Western Part of Kerman Area, Iran. Open Journal of Geology, 5, 489-498.
 Alizadeh, H., Arian, M., Lotfi, M., Ghorashi, M. and Ghorbani, M. (2015) Determination of Porphyry Copper Deposit Locations Using Photo Lineament Factor in Northern Parts of the Dehaj-Sardoiyeh Belt. Geosciences, 24, 247-252.
 Aram, Z. and Arian, M. (2016) Active Tectonics of the Gharasu River Basin in Zagros, Iran, Investigated by Calculation of Geomorphic Indices and Group Decision Using Analytic Hierarchy Process (AHP) Software. Episodes, 39, 39-44.
 Arian, M. and Khodabakhshnezhad, A. (2015) Sedimentary Environments Can Be Changed by Geotechnology (Case Study: A Morphotectonic Idea for Design of Extensive Artificial Bay on the Iranian Plateau). International Journal of Geosciences, 6, 487-496.
 Arian, M. and Noroozpour, H. (2015) Seismic Activity and Fractal Geometry of Kareh Bas Fault System in Zagros, South of Iran. Open Journal of Geology, 5, 291-299.
 Arian, M. and Pourkermani, M. (2001) Rivers Morphology and Active Tectonic (Reviewing the Current Status of GhezelOzon River in the Province of Zanjan). Proceedings of the 5th Conference of Geological Society of Iran, Tehran, 28-30 August 2001, 556.
 Arian, M. and Qorashi, M. (2006) The Movement Potential Evaluation of the Major Quaternary Faults in Alborz-Central Iran Border Zone, from the East of Tehran to the East of Semnan. Journal of Geosciences, Geological Survey of Iran, 15, 184-188.
 Arian, M., Ahmadnia, A., Qorashi, M. and Pourkermani, M. (2002) Structural Analysis of Mengharak Transcurrent Fault System in Zagros, Iran. Special GEO 2002 Conference Issue Geoarabia, 7, 209-210.
 Arian, M., Alizadeh, H. and Noroozpour, H. (2011) Satellite Geometry of Faults and Fractures and Its Relationship with Porphyry Deposits in Northern Parts of Dahaj-Sardoiyeh Belt, South of Iran. Indian Journal of Science and Technology, 4, 1303-1306.
 Arian, M., Pourkermani, M., Khodabakhshnezhad, A. and Noroozpour, H. (2011) Investigation of Oil Trap in the Asmari Anticline (Zagros, Iran). Indian Journal of Science and Technology, 4, 1696-1699.
 Arian, M., Pourkermani, M., Qorashi, M. and Ghasemi, M.R. (2003) North Semnan Fault System and Its Role on Basin Division. Proceedings of the 8th Symposium of Geological Society of Iran, Shahrood, 4-6 September 2003, 11-17.
 Arian, M., Pourkermani, M., Sistanipour, A. and Noroozpour, H. (2011) Kinematic Significance of Fold- and Fault-Related Fracture Systems in the Rafsanjan’s Northeast Highlands (Central Iran). Journal of Basic and Applied Scientific Research, 1, 3398-3406.
 Arian, M., Pourkermani, M., Sistanipour, A. and Noroozpour, H. (2011) Seismicity and Fault Segmentation of Bafq-Baghin Fault System (Central Iran). Journal of Applied Environmental and Biological Sciences, 1, 382-396.
 Arian, M., Qorashi, M., Pourkermani, M. and Ahmadnia, A. (2003) Fractal Analysis of Mengharak Transcurrent Fault System in Zagros, Iran. Proceedings of the 4th International Conference on Seismology and Earthquake Engineering, Tehran, 12- 14 May 2003, 23.
 Asadian, F. and Arian, M. (2009) Identification of Diapiric Provinces of Central Iran through Geological and Geographical Analysis. International Journal of Agriculture Environment & Biotechnology, 2, 3443-3451.
 Bagha, N., Arian, M., Ghorashi, M., Pourkermani, M., El Hamdouni, R. and Solgi, A. (2014) Evaluation of Relative Tectonic Activity in the Tehran Basin, Central Alborz, Northern Iran. Geomorphology, 213, 66-87.
 Bagha, N., Ghorashi, M., Arian, M., Pourkermani, M. and Solgi, A. (2015) Neotectonic Analysis of Mosha-North Tehran Fault Zone, Based on Morphotectonic Features, Central Alborz, Northern Iran. Geosciences, 24, 41-52.
 Baharvand, S., Pourkermani, M., Ajalloian, R., Arian, M. and Nouryazdan, A.R. (2010) Seymareh Landslide and Its Role in Environmental and Geomorphologic Changes of the Pole-Dokhtar Area. Journal of the Earth, 4, 13-24.
 Bull, W.B. and McFadden, L.D. (1977) Tectonic Geomorphology North and South of the Garlock Fault, California. In: Doehring, D.O., Ed., Geomorphology in Arid Regions. Proceedings of the Eighth Annual Geomorphology Symposium, State University of New York, Binghamton, 115-138.
 Daryani, N.J., Arian, M. and Omran, N.R. (2015) Tectonics and Mineralisation of Copper in the Ardestan-Kahang Area, Central Iran by Remote Sensing. Open Journal of Geology, 5, 188-196.
 Ehsani, J. and Arian, M. (2015) Quantitative Analysis of Relative Tectonic Activity in the Jarahi-Hendijan Basin Area, Zagros, Iran. Geosciences Journal, 19, 751-765.
 El Hamdouni, R., Irigaray, C., Fernandez,T., Chacón, J. and Keller, E.A. (2008) Assessment of Relative Active Tectonics, Southwest Border of Sierra Nevada (Southern Spain). Geomorphology, 96, 150-173.
 Eshghi, Z., Arian, M. and Pourkermani, M. (2012) Structural Investigation on the Lak Mining Area (Bueen Zahra) Based on Remote Sensing, Used for Its Mineralization. Journal of the Earth, 6, 145-155.
 Farrokhnia, A.R., Pirasteh, S., Pradhan, B., Pourkermani, M. and Arian, M. (2011) A Recent Scenario of Mass Wasting and Its Impact on the Transportation in Alborz Mountains, Iran Using Geo-Information Technology. Arabian Journal of Geosciences, 4, 1337-1349.
 Hadizadeh, A., Arian, M. and Ganjouyan, M.A. (2011) Analysis Geometry Dashtak Detachment Zone in the Dashtak, Salamati and Sepidar Anticlines from Interior and Sub Coastal Fars Area. Journal of the Earth, 6, 33-44.
 Hare, P.W. and Gardner, T.W. (1985) Geomorphic Indicators of Vertical Neotectonism along Converging Plate Margins, Nicoya Peninsula, Costa Rica. In: Morisawa, M. and Hack, J.T., Eds., Tectonic Geomorphology. Proceedings of the 15th Annual Binghamton Geomorphology Symposium, Allen and Unwin, Boston, 123-134.
 Keynezhad, A., Pourkermani, M., Arian, M., Saeedi, A. and Lotfi, M. (2010) Research on Fractures in North of the Torud-Moalleman Area (Central Iran, Southeastern of Damghan) and Their Relation with Mineralization. Journal of the Earth, 5, 81-95.
 Khavari, R., Arian, M. and Ghorashi, M. (2009) Neotectonics of the South Central Alborz Drainage Basin, in NW Tehran, N Iran. Journal of Applied Sciences, 9, 4115-4126.
 Khosroshahizadeh, S., Pourkermani, M., Almasian, M., Arian, M. and Khakzad, A. (2016) Lineament Patterns and Mineralization Related to Alteration Zone by Using ASAR-ASTER Imagery in Hize Jan-Sharaf Abad Au-Ag Epithermal Mineralized Zone (East Azarbaijan—NW Iran). Open Journal of Geology, 6, 232-250.
 Khosroshahizadeh, S., Pourkermani, M., Almasiyan, M., Arian, M. and Khakzad, A. (2015) Evaluation of Structural Patterns and Related Alteration and Mineralization Zones by Using ASAR-ASTER Imagery in Siyahrood Area (East Azarbaijan—NW Iran). Open Journal of Geology, 5, 589-610.
 Bagheri, M., Feiznia, S., Arian, M., Shabanian, R. and Mahari, R. (2013) Continental Trace Fossils in the Semnan Area (Northern Iran). Open Journal of Geology, 3, 54-61.
 Mahmoodi, M., Bahroudi, A., Ghorbani, M. and Arian, M. (2013) Preliminary Exploration of Copper Minerals in Jebal Barez Mountains, Iran. Open Journal of Geology, 3, 201-208.
 Maleki, Z., Arian, M., Solgi, A. and Ganjavian, M.A. (2013) Sediment Deformations on Strike Slip Fault Blocks and Analogue Modeling: A Case Study of the Nezamabad Fault, Interior Fars, Zagros. Journal of Sciences (Islamic Azad University), 89, 39-51.
 Maleki, Z., Arian, M. and Solgi, A. (2014) Structural Style and Hydrocarbon Trap of Karbasi Anticline, in the Interior Fars Region, Zagros, Iran. Solid Earth Discussions, 6, 2143-2167.
 Maleki, Z., Arian, M. and Solgi, A. (2015) Folding Pattern in the Fars Province, Zagros Folded Belt: Case Study on the Karbasi and Khaftar Anticlines, Interior Fars, Iran. Solid Earth Discussions, 7, 2347-2379.
 Maleki, Z., Arian, M., Solgi, A. and Ganjavian, M.A. (2014) The Elements of Fold Style Analysis in the Khaftar Anticline, Zagros, Iran. Open Journal of Geology, 4, 79-92.
 Mardani, Z., Ghorashi, M. and Arian, M. (2011) Geomorphic Signatures of Active Tectonics in the Talaghanrud, Shahrudand Sefidrud Drainage Basins in Central Alborz, N Iran. Geosciences, 20, 159-166.
 Mashal, M., Pour Kermani, M., Charchi, A., Almasian, M. and Arian, M. (2013) Pattern of Structural Geology Underground in Eastern of North Dezfol Embayment. Advances in Environmental Biology, 7, 260-268.
 Mirzeinaliyazdi, S.H., Pourkermani, M., Arian, M. and Almasian, M. (2012) Geometrical Analysis of Fractures in Sabzevar Ophiolite Zone. Journal of Geotechnical Gology (Applied Geology), 7, 359-371.
 Mirzeinaliyazdi, S.H., Pourkermani, M., Arian, M. and Karkheiran, A. (2012) Determination of Stress Orientation in Sabzevar Ophiolite Zone in (Khorasan Razavi Province, Iran). Indian Journal of Science and Technology, 5, 3500-3505.
 Mosavi, E. and Arian, M. (2015) Neotectonics of Kashaf Rud River, NE Iran by Modified Index of Active Tectonics (MIAT). International Journal of Geosciences, 6, 776-794.
 Mousavi, E., Arian, M. and Ghorashi, M. (2017) Investigation of T Factor Variations along Atrak River to the Caspian Sea. Open Journal of Marine Science, 7, 35-50.
 Nazemi, M., Ghorashi, M., Ghassemi, M.R. and Arian, M. (2015) Morphotectonics Features of Alluvial Fans Associated with Active Tectonics (Shotori Mountains, East of Tabas-Central Iran). Geosciences, 24, 91-100.
 Nouri, R. and Arian, M. (2015) Structural Control on the Distribution of Hydrothermal Alteration Zones and Mineralization in Dastjerdeh Area Based on Remote Sensing Data, NW Iran. Bulletin of the Georgian National Academy of Sciences, 9, 79-86.
 Nouri, R., Afzal, P., Arian, M., Jafari, M. and Feizi, F. (2013) Reconnaissance of Copper and Gold Mineralization Using Analytical Hierarchy Process in the Rudbar 1:100,000 Map Sheet, Northwest Iran. Journal of Mining and Metallurgy, 49, 9-19.
 Nouri, R., Jafari, M.R., Arian, M., Feizi, F. and Afzal, P. (2013) Correlation between Cu Mineralization and Major Faults Using Multifractal Modelling in the Tarom Area (NW Iran). Geologica Carpathica, 64, 409-416.
 Nouri, R., Jafari, M.R., Arian, M., Feizi, F. and Afzal, P. (2013) Prospection for Copper Mineralization with Contribution of Remote Sensing, Geochemical and Mineralographical Data in Abhar 1:100,000 Sheet, NW Iran. Archives of Mining Sciences, 58, 1071-1084.
 Poroohan, N., Poukermani, M. and Arian, M. (2009) An Assessment on Correlations of Seismotectonic Parameters Preceding and Following Roudbar-Manjil Earthquake (Gilan, North of Iran). Australian Journal of Basic & Applied Sciences, 3, 2643-2652.
 Poroohan, N., Pourkermani, M. and Arian, M. (2013) An Assessment of Relationship in F-Parameter and Paleostress Fields in Heterogeneous Lithologies: Roudbar Area (Northwest of Iran). Australian Journal of Basic & Applied Sciences, 7, 933-942.
 Pourkermani, M., Mohajjel, M., Solgi, A., Arian, M. and Nadri, R. (2012) Active Tectonics of South Qom, a Hazard for New Residential Areas. Journal of Geotechnical Gology (Applied Geology), 8, 203-213.
 Rafiee, P., Baghbani, D., Aghanabati, A. and Arian, M. (2015) Microbiostratigraphy and Lithostratigraphy of the Upper Permian Dalan Formation in Kuh-E-Surmeh (Zagros Basin, Southwest Iran). International Journal of Geography and Geology, 4, 68-73.
 Rockwell, T.K., Keller, E.A. and Johnson, D.L. (1985) Tectonic Geomorphology of Alluvial Fans and Mountain Fronts near Ventura, California. In: Morisawa, M., Ed., Tectonic Geomorphology. Proceedings of the 15th Annual Geomorphology Symposium, Allen and Unwin Publishers, Boston, 183-207.
 Sadeghi, R., Saeedi, A., Arian, M., Ghorashi, M. and Solgi, A. (2015) Comparison of Strain Ellipsoid Shape in the South of Ardabil Range (NW), Based on the Results of the Magnetic Susceptibility Anisotropy and Paleostress Methods. Open Journal of Geology, 5, 611-622.
 Strahler, A.N. (1952) Hypsometric (Area-Altitude) Analysis of Erosional Topography. Geological Society of America Bulletin, 63, 1117-1142.
 Tajali, S. and Arian, M. (2016) Petrophysical Evaluation and the Effect of Shale Layers on Net Pay Zone Thickness in the Marun Oil Field, Iran. Open Journal of Geology, 6, 763-773.
 Vaseghi, H., Maleki, Z. and Arian, M. (2016) Structural Style in the Zagros Fold-Thrust Belt: The Gavbast Anticline, Coastal Fars. Open Journal of Geology, 6, 109-116.