Australian Journal of Basic and Applied Sciences, 4(6): 969-993, 2010 ISSN 1991-8178

Active Tectonics of the South Central (North )

123Khavari, R. Arian, M. Ghorashi, M

1Islamic Azad University (IAU), Behbahan Branch, Behbahan, Iran 2Islamic Azad University, Sciences and research branch, , Iran 3Geological Survey of Iran, Tehran, Iran

Abstract: The paper present a method for evaluating relative active tectonics based on geomorphic indices useful in evaluating morphology and topography. Indices used include: stream length-gradient index (SL), drainage basin asymmetry (Af), hypsometric integral (Hi), ratio of valley-floor width to valley height (Vf), index of drainage basin shape (Bs), and index of mountain front sinuosity (Smf). Results from the analysis are accumulated and expressed as an index of relative active tectonics (Iat), which we divide into four classes from relatively low to highest tectonic activity. The study area along the south flank of the central Alborz mountain range in north Iran is an ideal location to test the concept of an index to predict relative tectonic activity on a basis of area rather than a single valley or mountain front. The recent investigations show that neotectonism has played a key role in the geomorphic evolution of this part of the Alborz mountain range. Geomorphic indices indicate the presence of differential uplifting in the geological past. The area surrounding the Amirkabir lake shows very high relative tectonic activity.

Key words: Tectonic geomorphology; Geomorphic indices of active tectonics; drainage basin; Central Alborz.

INTRODUCTION

Surrounding the south Caspian Basin, the narrow Alborz mountain of 100 km wide extends for about 2000 km from Lesser Caucasus in the northwest to the Paropamisus mountains in northern Afghanistan, to the east and shows strong tectonic activity (Berberian and Yeats, 2001). The regional seismic record is characterized by high frequency of relatively small magnitude earthquakes (less than magnitude 4) with infrequent, large, catastrophic earthquakes. The study of active tectonics, and in particular those areas with relatively high activity, in the Holocene and late Pleistocene is important to evaluate the earthquake hazard (Keller and Pinter, 2002). On a regional scale, obtaining rates of active tectonics is difficult or even knowing where to go in a particular region for quantitative studies to obtain rates. The approach of this paper is to provide a quantitative method to focus on areas for more detailed work to establish rates of active tectonics. We use geomorphic indices of active tectonics, known to be useful in active tectonic studies (Bull and McFadden, 1977; Azor et al., 2002; Keller and Pinter, 2002; Silva et al., 2003; Molin et al., 2004). This methodology has been previously tested as a valuable tool in different tectonically active areas, such as SW USA (Rockwell et al., 1985), the Pacific coast of Costa Rica (Wells et al., 1988), and the Mediterranean coast of Spain (Silva, 1994). In detail, the combination of the Smf and Vf indexes allows individual mountain fronts to be assigned different tectonic activity classes (Class 1 to Class 3) developed under decreasing uplift rates (Bull and McFadden, 1977; Rockwell et al., 1985). Most studies of geomorphic indices have concentrated on specific indices at specific sites, such as a drainage basin or mountain front. With the exception of the stream length-gradient index (SL), most of the indices are not spatially analyzed over a region. The objective of this paper is to quantify several geomorphic indices of relative active tectonic and topographic development to produce a single index that can be used to characterize relative active tectonics (Hamdouni et al., 2007). For this purpose, we will present the tectonic geomorphic analysis of indices followed by a discussion of the active tectonics based upon geomorphic analysis.

Regional Setting of the Study Area: The drainage basin of the south Central Alborz in north Iran has an area about 1085 Km and a

Corresponding Author: Khavari, R., Islamic Azad University (IAU), Behbahan Branch, Behbahan, Iran Fax: +986714220109 E-mail: [email protected] 969 Aust. J. Basic & Appl. Sci., 4(6): 969-993, 2010 length and width, 59 Km and 37 Km respectively (Figure 1). The is drawing from the Gachsar at 2200 m over sea level to Amirkabir lake and continues southward to the Karaj alluvial fan close to 1360 m over sea level. According to Tchalenko et al (1974), study area extends over two units of the Alborz subdivision (Figure 2); the High Alborz, a complex folded zone of Precambrian, Paleozoic and Mesozoic sedimentary rocks thrust southwards over Eocene rocks in the Border Folds zone, forms the hanging-wall of the Mosha fault (Ehteshami Moinabadi and Yassaghi, 2006) and the Border Folds zone contains the Eocene Karaj formation which crops out in a series of synclines in the footwall of fault (Figure 1). The Palaeocene Fajan continental conglomerates throughout northern Iran marks the base of the Eocene Karaj formation (Stocklin and Setudehnia, 1977). The North Tehran fault upthrusts the rocks of the Karaj formation southwards over the alluvial deposits of the Pediment zone (Figure 2). Alluvial deposits are rare in the Karaj river valley, so it flows over a channel of exposed bedrock over much of its length. This shows that the Karaj river is a bed rock river in that driving forces tend to be greater than resisting forces, and most of deposits supplied transport away.

Morphometric Analysis and Geomorphic Indices of Active Tectonics: Several geomorphic indices may be used to analyze topography as well as relative tectonic activity. Individual indices are based on analysis of the drainage network or mountain fronts. The indices represent a quantitative approach to differential geomorphic analysis related to erosion and depositional processes that include the river channel, long profile, and valley morphology as well as tectonically derived features, such as fault scarps. Indices of active tectonics may detect anomalies in the fluvial system or along mountain fronts. These anomalies may be produced by local changes from tectonic activity resulting from uplift or subsidence (Hamdouni et al., 2007). The research design is to analyze several different indices in subbasins of the Karaj River basin (Figure 3) and break them into tectonic classes based upon the range of values of individual indices. These are then summed and averaged and arbitrarily divided into classes of relative tectonic activity over the study area (Hamdouni et al, 2007).

Stream Length-gradient Index (SL): Development of topography results from an adjustment between processes of erosion such as streams and rivers flow over rocks and soils of variable strength (Hack, 1973). The adjustment eventually reaches a dynamic equilibrium. The stream length-gradient index (SL) was defined by Hack (1973) in a study of the role of rock resistance in streams of the Appalachian Mountains of the southeastern United States. The SL index is defined as:

SL = (Äh/Äl)l (1) where Äh/Äl is the local slope of the channel segment being evaluated and l is the channel length from the divide to the midpoint of the channel reach for which the index is calculated. The SL index can be used to evaluate relative tectonic activity. The SL index will increase in value as rivers and streams flow over active uplifts and may have lesser values when flowing parallel to features such as valleys produced by strike–slip faulting (Keller and Pinter, 2002). Values of the SL index over the study area, determined from digital elevation models and geographic information system (GIS), are shown on Figure 4. According to Hamdouni et al 2007, in order to discriminate values at the index related to rock resistance, different levels of average rock strength were defined (by rock type and field observation) from very low strength (alluvial deposits), low strength (slope deposits), moderate strength (siltstone, shale), high strength (sandstone, conglomerate, limestone, and tuff), and very high strength (quartzite, and monzodiorit-monzogabbro). The observed SL index anomalies were then plotted on the map of the relative strength of materials (Figure 5), and their relation to rock strength were analyzed utilizing GIS applications (Figures 6, 7, 8 and 9). Based upon the quantitative SL indices linked to relative rock resistance described above with field observations suggest that: (i)Along the N border of the Karaj drainage basin, values of the SL index show a variable distribution. Along the Varangehrood and Velayatrood rivers, Vashkestanak and Sutak creeks on the eastern part of the Karaj river high indices are not associated with particularly resistant rocks, and so we interpret these anomalies in the SL index to be a tectonic signal (Hamdouni et al 2007) (Figure 6). Several locations along the western part of the Karaj river also have anomalously high SL index values on relatively resistance rocks. Along the Azadbar creek, indices increase where it crosses the mountain front with the Taleghan fault. Along the

970 Aust. J. Basic & Appl. Sci., 4(6): 969-993, 2010

Hasanakdar creek, the highest values of the indices results from active folding of a Pleistocene alluvial fan (Figure 6). Another anomaly, farther downstream along the Hasanakdar creek, exists where the river crosses the hard limestone. (ii)Along the south and southwestern portions of the study area, SL indices tend to be relatively higher than the N border. Anomalous values of the indices along the all rivers and creeks in this part are related to outcrops of the resistant rocks found along the rivers and creeks profiles as well as tectonic activity (Figure 7). (iii)Along the southeastern portion of the Karaj drainage basin the values of the SL index are very high. The highest and perhaps most anomalous values of the index are along the Shahrestanak river on the eastern part of the Karaj river (Figure 8)These high indices are related to changes in rock resistance not associated with tectonic activity. Along the Karaj river the values of the SL index are very low in upstream, because of low strength of rocks. High values of the index in downstream are related to changes in rock resistance. The SL index values increase downriver and are related to the very strong rocks as demonstrated by the observed profile (Figure 9). The lowest part of the river show very low value of the index.

Asymmetric Factor (Af): The asymmetric factor (Af) is a way to evaluate the existence of tectonic tilting at the scale of a drainage basin. The method may be applied over a relatively large area (Hare and Gardner, 1985; Keller and Pinter, 2002). Af is defined by

Af = 100(Ar / At) (2) where Ar is the area of the basin to the right (facing downstream) of the trunk stream and At is the total area of the drainage basin. If a basin has developed under stable conditions with little or no tilting, the Af factor is close to 50. The index is sensitive to change in inclination perpendicular to the channel direction. An Af factor above or below 50 may result from basin tilting, resulting either from active tectonics or lithologic structural control differential erosion, as for example the stream slipping down bedding plains over time. The values shown in Table 3 for Af include the Af-50, which is the amount of difference between the neutral value of 50 and the observed value. For the purpose of evaluating the relative active tectonics, the absolute difference is what is important, and values of Af-50 range from about 0 to 36. Structural control of the orientation of schistocity or bedding may play a significant role in the development of basin asymmetry (Hamdouni et al., 2007). Inclination of schistocity or bedding allows for preferred migration of the valley in the down-dip direction, producing an asymmetric valley, so those values for which the rock structure is an obvious factor should be disregarded (Hamdouni et al., 2007). In the study area, there are no basins that have the asymmetric factor related to structural control (Figure 10). Af values range from moderate to high in the study area (Table 3). In general, the most prominent asymmetry is found in the southern part of the Karaj drainage basin and the area surrounding the Amirkabir lake.

Hypsometric Integral (Hi): The hypsometric integral is an index that describes the distribution of elevation of a given area of a landscape (Strahler, 1952). The integral is generally derived for a particular drainage basin and is an index that is independent of basin area. The index is defined as the area below the hypsometric curve and thus expresses the volume of a basin that has not been eroded. The simple equation that may be used to calculate the index (Pike and Wilson, 1971; Mayer, 1990; Keller and Pinter, 2002) is

Hi = (average elevation – min. elevation) ' (max. elevation – min. elevation). (3)

The values of elevation necessary for the calculation are obtained from a digital elevation model. The average elevation is from 50 points of elevation taken at random from the drainage basin. The hypsometric integral does not relate directly to relative active tectonics. This index is similar to the SL index in that rock resistance as well as other factors affects the value. High values of the index generally mean that not as much of the uplands have been eroded, and may suggest a younger landscape, perhaps produced by active tectonics (Hamdouni et al., 2007). High values of Hi could also result from recent incision into a young geomorphic surface produced by deposition. In our analysis of Hi, we consider whether the curve is convex in its upper portion, convex to concave, or convex in the lower portion, as well as the value of the index itself (Hamdouni

971 Aust. J. Basic & Appl. Sci., 4(6): 969-993, 2010 et al., 2007). We assume that if part of the hypsometric integral is convex in the lower portion, it may relate to uplift along a fault or perhaps uplift associated with recent folding. High values of the index are possibly related to young active tectonic and low values are related to older landscapes that have been more eroded and less impacted by recent active tectonics. In general, high values of the hypsometric integral are convex, and these values are generally > 0.5. Intermediate values tend to be more concave–convex or straight, and generally have values between 0.4 and 0.5. Finally, lower values (< 0.4) tend to have concave shapes. Analysis of the hypsometric integral in the study area was based upon digital elevation models utilizing GIS applications. Results are shown on Figure 11.

Ratio of Valley Floor Width to Valley Height (Vf): Vf is defined as the ratio of the width of the valley floor to its average height (Bull and McFadden, 1977; Bull, 1978) and is computed by

Vf = 2Vfw/ [(Eld – Esc)] + (Erd – Esc)] (4) where Vf is the ratio of valley floor width to valley height; Vfw is the width of the valley floor; Eld is the elevation of the divide on the left side of the valley; Erd is the elevation on the right side; and Esc is the average elevation of the valley floor. This index differentiates between valleys with a wide floor relative to the height of valley walls with a “U” shape compared to narrow, steep valleys with a “V” shape. Valleys with a U shape generally have high values of Vf, whereas V-shaped valleys with relatively low values. Because uplift is associated with incision, the index is thought to be a surrogate for active tectonics where low values of Vf are associated with higher rates of uplift and incision. The index is a measure of incision and not uplift; but in an equilibrium state, incision and uplift are nearly matched. The value of Vf is calculated for the main valleys that cross mountain fronts of the study area (Figure 12). Calculation of the index is done at a prescribed distance upstream from the mountain front (Silva et al., 2003). In this area a distance varying from 1 to 1.5 km, depending on the size of the selected drainage basin. It has been observed that the valleys often narrow upstream from the mountain front (Ramírez-Herrera, 1998). As a result, values of Vf vary depending on basin size, stream discharge, and rock type encountered (Hamdouni et al., 2007). Therefore, values of Vf should be compared for similar geologic conditions. Values of Vf for the study area are shown in Table 3, and locations where calculations of the index are made are shown in Figure 12. Classification of the index is down based upon the Hamdouni et al., 2007. Values of Vf vary from a low of 0.043 for the Daryug Creek north of Karaj basin, where it is deeply incised into hard tuff bedrock, to a high of 5.141 at Mazon Creek east of Karaj basin (Figure 12). In general, the values of Vf are relatively low for most of the study area, with the exception of the lower-lying areas in the NW, SE and S parts of the study area. A similar analysis, carried out by Silva et al. (2003) in the Eastern Betic Cordillera (SE Spain), suggests that V-shaped valleys with low Vf values < 1 develop in response to active uplift, and that broad U-shaped valleys with high Vf values > 1 indicate major lateral erosion, due to the stability of base level or to tectonic quiescence.

Index of Drainage Basin Shape (Bs): Relatively young drainage basins in active tectonic areas tend to be elongated in shape normal to the topographic slope of a mountain. With continued evolution or less active tectonic processes, the elongated shape tends to evolve to a more circular shape (Bull and McFadden, 1977). Horizontal projection of basin shape may be described by the elongation ratio, Bs (Cannon, 1976; Ramírez-Herrera, 1998) expressed by the equation

Bs = Bl ' Bw (5) where Bl is the length of the basin measured from the headwaters to the mouth, and Bw is the width of the basin measured at its widest point. High values of Bs are associated with elongated basins, generally associated with relatively higher tectonic activity. Low values of Bs indicate a more circular-shaped basin, generally associated with low tectonic activity. Rapidly uplifted mountain fronts generally produce elongated, steep basins; and when tectonic activity is diminished or ceases, widening of the basins occur from the mountain front up (Ramírez-Herrera, 1998). Bs was calculated for 62 subbasins in the study areas. The results are shown in Table 3 and values range from 1.24 to 5.21. The highest values are along the S border of the Karaj basin.

972 Aust. J. Basic & Appl. Sci., 4(6): 969-993, 2010

Index of Mountain Front Sinuosity (Smf): Index of mountain front sinuosity Smf (Bull and McFadden, 1977; Bull, 1978) is defined by

Smf = Lmf ' Ls (6) where Lmf is the length of the mountain front along the foot of the mountain where a change in slope from the mountain to the piedmont occurs; and Ls is the straight line length of the mountain front. Smf represents a balance between erosive processes tending to erode a mountain front, making it more sinuous through streams that cut laterally and into the front and active vertical tectonics that tend to produce straight mountain fronts, often coincidental with active faults or folds (Bull and McFadden, 1977; Keller, 1986). That is, mountain fronts associated with active tectonics and active uplift are relatively straight with low values of Smf; but if the rate of uplift is reduced or ceases, then erosional processes along the mountain front produce a more sinuous front and thus lower value of Smf. Values of Smf are readily calculated from topographic maps or aerial photography. However, the value obtained depends upon the scale (Bull and McFadden, 1977). Small-scale maps (1:250,000) produce approximate values of Smf, while larger scale topographic maps and aerial photography have higher resolution and are more appropriate for assessment of Smf. Values of Smf approach 1.0 on the most tectonically active fronts, whereas Smf increases if the rate of uplift is reduced and erosional processes begin to form a front that becomes more irregular with time. Smf values lower than 1.4 indicate tectonically active fronts (Rockwell et al., 1985; Keller, 1986) while higher Smf values (> 3) are normally associated with inactive fronts in which the initial range–front fault may be more than 1 km away from the present erosional front (Bull and McFadden, 1977). This index was also calculated in the Eastern Betic Cordillera by Silva et al. (2003) using a topographic map at scale 1:50,000 from which they obtained values between 1.17 and 3.51. They considered values below 1.4 as indicative of active tectonics until values above 3 were considered as indicating inactive fronts. In this paper, 29 mountain fronts with vertical of relief more than 20 m (Hamdouni et al., 2007) are evaluated (Figure 13). Values of Smf are shown in Table 2 and range from 1.0034 to 1.78. The lowest values of Smf are associated with the area surrounding the Amirkabar lake coincidental with the Emamzadehdavood fault. However, almost all of the mountain fronts have relatively moderate to high values of Smf. The considered fronts are shown in Figure 13 and consist of faults parallel to mountain trend.

Discussion: In this study we used the method suggested by Hamdouni et al., 2007 to evaluate an index over an area that represents relative tectonic activity (Iat). We divide the various indices into three classes, with class one being high activity and class three being low activity (Table 3). Iat is obtained by the average of the different classes of geomorphic indices (S/n) and divided into four classes, where class 1 is very high tectonic activity with values of S/n between 1 and 1.5; class 2 is high tectonic activity with values of S/n > 1.5 but < 2; class 3 is moderately active tectonics with S/ n > 2 but < 2.5; and class 4 is low active tectonics with values of S/n > 2.5. The averaging of the indices of the active tectonics S/n and values of Iat are summarized in Table 3 for 62 drainage subbasins in the study area (see Figure 2 for basin locations). The distribution of the indices defines areas associated with different mountain fronts and estimates of relative rates of tectonic activity (Figure 14). Within the study area, about 7.8% (84.7 km2) is class 1 (very high relative tectonic activity) as measured by Iat; 46.4% (503.37 km2) shows high relative tectonic activity as measured by Iat (class 2); 42% (454.036 km2) has moderate values of tectonic activity in terms of Iat (class 3); and 3.8% (41.44 km2) has the lowest values of relative tectonic activity (class 4) based upon Iat. Thus, more than of half of the study area is classified into classes 2 or 1 of high to very high tectonic activity in terms of the apparent geomorphic response. In different tectonic environments with greater rates of active tectonics, the values of indices would differ as well as their range in value. There are three domains of tectonic activity in the study area: (1) the lowest class value (very high tectonic activity) for Iat occurs in the area surrounding the Amirkabir Lake, because this zone is located on the active Varishsangan anticline and the Purkan-Vardij fault makes the southern border of that (Figure 15). (2) Although it is expected that the north part of the Mosh fault, the High Alborz Zone, shows high tectonic activity, some parts of this zone and the north part of the Alborz Border Folds with moderate strength lithology, have class of Iat suggesting moderate tectonic activity (Figures 5 and 15). (3) the low class value (high tectonic activity) in northern part of the basin. The high class values (low tectonic activity) for Iat mainly occur in the southern part of the Karaj drainage basin, because of its location in the north part of the Pediment Zone or frontal basin (Figures 1 and 15). Other areas with low tectonic activity are located on the low strength geological setting or the places between faults.

973 Aust. J. Basic & Appl. Sci., 4(6): 969-993, 2010

However, the methodology would provide an index based on area that estimates relative tectonic activity as it has for the study area in N Iran. The proposed GIS methodology allows a map showing relative tectonic activity of the landscape to be produced. The classification used in this paper for each geomorphic index is based upon Hamdouni et al., 2007 (Table 1).

Fig. 1: Geographical and geological setting of the study area.

Fig. 2: Spatial relations of major structural elements and the Karaj drainage basin, N Iran (modified from Ganser and Hubber, 1962).

974 Aust. J. Basic & Appl. Sci., 4(6): 969-993, 2010

Fig. 3: Subbasins of the Karaj River basin and its reference number.

Fig. 4: SL index along the Karaj River drainage network.

Fig. 5: Distribution of SL index anomalies and the geological strength levels.

975 Aust. J. Basic & Appl. Sci., 4(6): 969-993, 2010

Fig. 6: Continue

976 Aust. J. Basic & Appl. Sci., 4(6): 969-993, 2010

Fig. 6: Some longitudinal river profiles in the N border of the Karaj drainage basin and the measured SL index.

977 Aust. J. Basic & Appl. Sci., 4(6): 969-993, 2010

Fig. 7: Continue

978 Aust. J. Basic & Appl. Sci., 4(6): 969-993, 2010

Fig. 7: Continue

979 Aust. J. Basic & Appl. Sci., 4(6): 969-993, 2010

Fig. 7: Continue

980 Aust. J. Basic & Appl. Sci., 4(6): 969-993, 2010

Fig. 7: Some longitudinal river profiles in the W and SW areas of the Karaj drainage basin and the measured SL index.

Fig. 8: Some longitudinal river profiles in the SE area of the Karaj drainage basin and the measured SL index.

981 Aust. J. Basic & Appl. Sci., 4(6): 969-993, 2010

Fig. 9: Longitudinal river profile of the Karaj river and the measured SL index.

Fig. 10: Map showing the lithologies of the study area.

982 Aust. J. Basic & Appl. Sci., 4(6): 969-993, 2010

Fig. 11: Continue

983 Aust. J. Basic & Appl. Sci., 4(6): 969-993, 2010

Fig. 11: Continue

984 Aust. J. Basic & Appl. Sci., 4(6): 969-993, 2010

Fig. 11: Continue

985 Aust. J. Basic & Appl. Sci., 4(6): 969-993, 2010

Fig. 11: Continue

986 Aust. J. Basic & Appl. Sci., 4(6): 969-993, 2010

Fig. 11: Continue

987 Aust. J. Basic & Appl. Sci., 4(6): 969-993, 2010

Fig. 11: Hypsometry curves of subbasins of the Karaj River. (A) is the total surface of the basin. (a) is the surface area within the basin above a given line of elevation (h), (H) is the highest elevation of the basin.

988 Aust. J. Basic & Appl. Sci., 4(6): 969-993, 2010

Fig. 12: Location of sections for the Vf calculations in the Karaj drainage basin.

Fig. 13: Mountain front segments with reference numbers delimited for the assessment of the Smf index (see Table 2 for mountain front names).

989 Aust. J. Basic & Appl. Sci., 4(6): 969-993, 2010

Fig. 14: Distribution of the Iat index of relative active tectonics in the Karaj River basin.

Fig. 15: Main faults and fold axes on the satellite image of the study area.

Conclusions: Geomorphic indices of active tectonics are useful tools to analyze the influence of active tectonics. These indices have the advantage of being calculated from GIS over large areas as a reconnaissance tool to identify geomorphic anomalies possibly related to active tectonics. This is particularly valuable in northern Iran where relatively little attention has been paid to active tectonics and rivers. Based upon values of the stream length- gradient index (SL), asymmetric factor (Af), hypsometric integral (Hi), ratio of valley-floor width to valley height (Vf), basin drainage shape (Bs), and index of mountain front sinuosity (Smf), we developed an overall index (Iat) that is a combination of the other indices that divides the landscape into four classes of relative tectonic activity. The area surrounding the Amirkabir lake shows very high relative tectonic activity.

990 Aust. J. Basic & Appl. Sci., 4(6): 969-993, 2010

Table 1: Values of the Smf (index of mountain front sinuosity) in the defined mountain fronts (Lmf: length of the mountain front along the foot of the mountain where a change in slope from the mountain to the piedmont occurs; Ls: straight line length of the mountain front) Mountain front No. Lmf (m) Ls (m) Smf Kandavan 1 8963.574271 8334.641911 1.08 Varangehrood1 2 9618.053615 9192.060859 1.05 Varangehrood2 3 15026.418142 14034.641604 1.07 Gachsar 4 9885.806534 8916.573272 1.11 Azadbar1 5 3154.277393 3015.383319 1.05 Azadbar2 6 5155.37581 4119.502699 1.25 Taleghan1 7 2359.021901 2350.394074 1 Taleghan2 8 9042.869223 8117.127483 1.11 Taleghan3 9 4168.763482 3878.870712 1.07 Taleghan4 10 3467.077885 3429.353634 1.01 Taleghan5 11 10928.530578 9900.279626 1.1 Hasanakdar 12 10351.765022 7963.854477 1.3 Mosha1 13 31589.771086 24033.97975 1.31 Mosha2 14 7022.347237 5470.804697 1.28 Mosha3 15 5651.361186 4505.153917 1.25 Mosha4 16 15747.877702 9255.300412 1.7 Maygun 17 9076.806436 7290.698026 1.24 Ahar 18 14393.224639 11541.134419 1.25 Ablaniz 19 8460.168137 7650.389293 1.11 Emamzadehdavood1 20 3430.307935 2984.803268 1.15 Emamzadehdavood2 21 3731.045725 3718.497979 1 Emamzadehdavood3 22 5528.913534 5159.301544 1.07 Amirkabir 23 8366.094891 7933.634999 1.05 Adaran1 24 9542.046939 7355.478665 1.3 Adaran2 25 8275.374131 8163.973355 1.01 Adaran3 26 8439.76017 8399.575601 1 Charan 27 8200.069203 7874.045154 1.04 Purkan-vardij 28 19289.595052 11703.611098 1.65 Baylaghan 29 7691.92553 4326.876107 1.78

Table 2: Geomorphic indexes classifications used in this study (Hamdouni et al., 2007). Class Smf Vf Sl Af Bs 1 < 1.1 < 0.5 High anomalous values *Af-50* > 15 > 4 2 1.1 - 1.5 0.5 - 1 Low anomalous values *Af-50* = 7 - 15 3-4 3 > 1.5 > 1 No anomalous *Af-50* < 7 < 3

Table 3: Classification of the Iat (relative tectonic activity index) in the subbasins of the Karaj River basin (SL: stream length- gradientindex; Af: drainage basin asymmetry; Hi: hypsometric integral; f: ratio of valley floor width to valley height; Bs: index of drainage basinshape; Smf: index of mountain-front sinuosity).

Ref. Basin Slaverage Class Af Class Bs Class Hi Class Smf Class Vf Class S/n Iat no of SL of Af of Bs of Hi of Smf of Vf class 1 Khozankala 370 2 8 2 3.46 2 0.47 2 1 1 — — 1.8 2 2 Azadbar 434 1 0.19 3 2.2 3 0.45 2 1.1 2 1.88 3 2.3 3 3 Kondor 227 3 -17 1 3.08 2 0.33 3 1.65 3 0.807 2 2.3 3 4 Disin 398 2 -13 2 2.59 3 0.46 2 1 1 — — 2 3 5 453 2 -5 3 2.44 3 0.41 2 1.31 2 0.135 1 2.16 3 6 Bandsar 351 2 -2 3 2.78 3 0.48 2 1.3 2 0.45 1 2.16 3 7 Chal 525 1 -31 1 2.31 3 0.56 1 1.04 1 0.354 1 1.3 1 8 Kondro 177 3 -30 1 2.64 3 0.43 2 — — 0.155 1 2 3 9 Syano 365 2 7 2 3.53 2 0.51 1 1 1 0.7 2 1.7 2 10 Gajar 300 3 -36 1 1.63 3 0.54 1 1.11 2 0.752 2 2 3 11 Bari 168 3 15 2 2.22 3 0.4 2 1.1 2 1.43 3 2.5 4 12 Middle Laniz 397 2 1.44 3 1.8 3 0.42 2 1 1 0.293 1 2 3 13 Bujdan 615 1 -4 3 2.91 3 0.53 1 1.31 2 0.427 1 1.83 2 14 Aftab kuh 528 1 -2 3 2.64 3 0.44 2 1.05 1 0.277 1 1.83 2 15 Kiasar 448 2 13 2 3.68 2 0.40 2 1.31 2 0.13 1 1.83 2 16 Gachsar 61 3 5 3 1.46 3 0.39 3 — — 0.404 1 2.3 3 17 Sarkhab 431 2 -1 3 1.48 3 0.57 1 1.08 1 0.875 2 2 3 18 Vashkestan 482 1 0 3 3.68 2 0.51 1 1.05 1 1.292 3 1.83 2 19 Neshastrood 607 2 0 3 2.68 3 0.55 1 — — 3.135 3 2 3 20 Asalak 191 3 15 2 1.75 3 0.37 3 1.05 1 0.893 2 2.3 3 21 Charan 707 1 -10.67 2 2.6 3 0.51 1 1.04 1 0.206 1 1.5 2 22 Shirkamar 385 2 -19 1 1.67 3 0.43 2 1.08 1 1.687 3 2 3 23 Khoshpelk 358 2 22 1 3.28 2 0.51 1 — — 0.505 2 1.6 2 24 Vasiyeh 367 2 -9 2 5.21 1 0.45 2 1.14 2 40.13 3 2 3

991 Aust. J. Basic & Appl. Sci., 4(6): 969-993, 2010

Table 3: Continue 25 Paralak 289 3 33 1 2.41 3 0.38 3 1.65 3 0.279 1 2.3 3 26 Labar 349 2 -6 3 1.93 3 0.48 2 1.11 2 0.113 1 2.16 3 27 Sharnaz 472 2 16 1 2.4 3 0.41 2 1.05 1 0.224 1 1.7 2 28 Garab 245 3 10 2 2.18 3 0.40 2 1.11 2 0.81 2 2.3 3 29 Sutak 576 1 10 2 2.32 3 0.52 1 1.07 1 1.294 3 1.83 2 30 Sarbasi 448 2 -2 3 2.64 3 0.47 2 1.11 2 2.393 3 2.5 4 31 Khor 470 2 -23 1 2.56 3 0.51 1 1.04 1 0.35 1 1.7 2 32 Razkan 545 1 -9 2 3.91 2 0.48 2 — — 0.139 1 1.6 2 33 Sarkhas 388 2 -12 2 2.51 3 0.48 2 1.05 1 0.291 1 1.83 2 34 Dardeh 581 2 -4 3 3.36 2 0.41 2 1.31 2 0.482 1 2 3 35 Sarintoro 398 2 -2 3 2.4 3 0.51 1 — — 0.786 2 2.2 3 36 Kandavan 222 3 9.79 2 1.81 3 0.48 2 1.11 2 0.124 1 2.16 3 37 Purkan 337 2 25 1 2.9 3 0.47 2 1.65 3 1.77 3 2.3 3 38 Doab 527 1 16 1 2.46 3 0.51 1 1.1 2 0.33 1 1.5 2 39 Daryog 427 2 -19 1 2.11 3 0.54 1 1.07 1 0.043 1 1.5 2 40 Avizar 534 1 -13 2 3.67 2 0.41 2 1.31 2 0.169 1 1.7 2 41 Nojan 312 2 4 3 2.27 3 0.57 1 — — 0.283 1 2 3 42 Abvarzan 421 1 27.87 1 3.4 2 0.47 2 1.31 2 0.27 1 1.5 2 43 Darband 489 2 -19.35 1 2.3 3 0.44 2 1.31 2 0.287 1 1.83 2 44 Hasanakdar 515 1 -2 3 2.22 3 0.51 1 1.3 2 0.589 2 2 3 45 Syvak 480 2 1.55 3 2.7 3 0.39 3 1.65 3 0.237 1 2.5 4 46 Nesa 383 2 8 2 2.57 3 0.46 2 1.11 2 1.191 3 2.3 3 47 Lower Laniz 425 2 -23 1 2.8 3 0.39 3 1 1 0.327 1 1.83 2 48 Kohneh deh 410 2 15 2 2.19 3 0.48 2 1.01 1 0.231 1 1.83 2 49 Upper Laniz 365 2 -8 2 1.24 3 0.54 1 1.15 2 0.385 1 1.83 2 50 Adaran 494 1 0 3 2.51 3 0.51 1 1.01 1 0.176 1 1.7 2 51 Morud 621 1 -7 2 4.57 1 0.51 1 1.05 1 0.146 1 1.17 1 52 Varangehrood 424 1 1.82 3 3.9 2 0.51 1 1.07 1 0.268 1 1.5 2 53 Sayedak 603 1 -27.47 1 2.4 3 0.43 2 1.31 2 0.123 1 1.7 2 54 Varian 444 2 -2 3 2.44 3 0.52 1 1.07 1 0.199 1 1.83 2 55 Baldareh 464 1 0 3 2.47 3 0.39 3 1.24 2 0.704 2 2.3 3 56 Shamushak 571 1 -15.59 1 2.4 3 0.51 1 1.07 1 0.183 1 1.3 1 57 Shahrestanak 839 1 -13.16 2 2.1 3 0.38 3 1.31 2 0.198 1 2 3 58 Kalarood 456 2 -5 3 3.46 2 0.45 2 1.31 2 0.431 1 2 3 59 Lilestan 517 2 -7 3 2.18 3 0.45 2 1.31 2 0.252 1 2.16 3

ACKNOWLEDGEMENTS

The authors would like to thank the Geological Survey of Iran for data supporting this research.

REFERENCES

Azor, A., E.A. Keller, R.S. Yeats, 2002. Geomorphic indicators of active fold growth: South Mountain- Oak Ridge Ventura basin, southern California. Geological Society of America Bulletin, 114: 745–753. Berberian, M. and R.S. Yeatz, 2001. Contribution of archeological data to studies of earthquake history in the Iranian Plateau. Journal of Structural Geology, 23: 563-584. Bull, W.B., 1978. Geomorphic Tectonic Classes of the South Front of the San Gabriel Mountains, California. U.S. Geological Survey Contract Report, 14-08-001-G-394, Office of Earthquakes, Volcanoes and Engineering, Menlo Park, CA. Bull, W.B. and L.D. McFadden, 1977. Tectonic geomorphology north and south of the Garlock fault, California. In: Doehring, D.O (eds), Geomorphology in Arid Regions. Proceedings of the Eighth Annual Geomorphology Symposium. State University of New York, Binghamton, 115-138. Cannon, P.J., 1976. Generation of explicit parameters for a quantitative geomorphic study of Mill Creek drainage basin. Oklahoma Geology Notes., 36(1): 3–16. Ehteshami Moinabadi, M. and A. Yassaghi, 2006. Geometry and kinematics of the Mosha Fault, south central Alborz Range, Iran, An example of basement involved thrusting. Journal of Asian Earth Sciences., 2: 928-938. EL Hamdouni, R., C. Irigaray, T. Fernandez, J. Chacon and E.A. Keller, 2007. Assessment of relative active tectonics, southwest border of the Sierra Nevada (southern Spain). Geomorphology. Article in press. Gansser, A. and H. Huber, 1962. Geological observations in the central Alborz, Iran, Schweizerische Mineralogische und Petrographische Mitteilungen, 42: 583-630. Hack, J.T., 1973. Stream-profiles analysis and stream-gradient index. Journal of Research of the U.S. Geological Survey., 1(4): 421–429.

992 Aust. J. Basic & Appl. Sci., 4(6): 969-993, 2010

Hare, P.W. and T.W. Gardner, 1985. Geomorphic indicators of vertical neotectonism along converging plate margins, Nicoya Peninsula, Costa Rica. In: Morisawa, M., Hack, J.T. (Eds.), Tectonic Geomorphology. Proceedings of the 15th Annual Binghamton Geomorphology Symposium. Allen and Unwin, Boston, MA, 123–134. Keller, E.A., 1986. Investigation of active tectonics: use of surficial Earth processes. In: Wallace, R.E. (Ed.), Active Tectonics, Studies in Geophysics. National Academy Press, Washington, DC, pp: 136–147. Keller, E.A. and N. Pinter, 2002. Active tectonics, Earthquakes, Uplift and Landscape. Prentice Hall: New Jersy. Mayer, L., 1990. Introduction to Quantitative Geomorphology. Prentice Hall, Englewood, Cliffs, NJ. Molin, P., F.J. Pazzaglia and F. Dramis, 2004. Geomorphic expression of active tectonics in a rapidly- deforming forearc, sila massif, Calabria, southern Italy. American Journal of Science, 304: 559–589. Pike, R.J. and S.E. Wilson, 1971. Elevation–relief ratio, hypsometric integral and geomorphic area-altitude analysis. Geological Society of America Bulletin, 82: 1079–1084. Ramírez-Herrera, M.A., 1998. Geomorphic assessment of active tectonics in the Acambay Graben, Mexican volcanic belt. Earth Surface Processes and Landforms, 23: 317-332. Rockwell, T.K., E.A. Keller and D.L. Johnson, 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, MA, 183–207. Silva, P.G., 1994. Evolución geodinámica de la depresión del Guadalentín desde el Mioceno superior hasta la Actualidad: Neotectónica y geomorfología. Ph.D. Dissertation, Complutense University, Madrid. Silva, P.G., J.L. Goy, C. Zazo and T. Bardajm, 2003. Fault generated mountain fronts in Southeast Spain: geomorphologic assessment of tectonic and earthquake activity. Geomorphology, 250: 203-226. Stocklin, J. and A. Setudehnia, 1977. Stratigraphic lexicon of Iran, Tehran, Geological Survey of Iran, 409. Strahler, A.N., 1952, Hypsometric (area-altitude) analysis of erosional topography. Geological Society of America Bulletin, 63: 1117–1142. Tchalenko, J.S., M. Berberian, H. Iranmanesh, M. Bailly. and M. Arsovsky, 1974. Tectonic framework of the Tehran region, Geological Survey of Iran Report., 26: 7-46. Wells, S.G., T.F. Bullard, T.M. Menges, P.G. Drake, P.A. Karas, K.I. Kelson, J.B. Ritter and J.R. Wesling,, 1988, Regional variations in tectonic geomorphology along segmented convergent plate boundary, Pacific coast of Costa Rica. Geomorphology, 1: 239–265.

993