@2024 Afarand., IRAN

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ISSN: 2538-4384    Geographical Researches 2020;35(1):83-94

Background
Morpho-tectonic indices of the basin are used for the evaluation of active tectonics. Since they are proper for the quick evaluation of enormous areas. Areas with active tectonics can be detected using such quantitative morphological measurements.
Previous Studies
Morphological indices were used in neo-tectonic activities by Horton (1945) for the first time and this method continued in other researchers' studies such as in Strahler's study in 1952. Yamani et al (2012) evaluated the qualitative morpho-tectonic evidence and quantitative morphological indices on the active tectonics of northern alluvial fans of Damghan. The result of this study shows the faults were active during the quaternary period. Abdideh et al (2011) evaluated the active tectonics of the Dez basin using morphological analysis. The results show tectonics rate is scattered due to continental collision of Iran and Arab blocks. Seif & Khosravi (2011), Bayati khatibi (2009), and Maghsoudi & Kamrani (2009) did similar studies in terms of morpho-tectonics.
Aim(s)
This study aimed to assess the active tectonics of the Dezful-Andimeshk basin using five indices including Asymmetry Factor (AF) Relative Relief (Bh ), Form Factor (Ff), Hypsometric Integral and curve (Hi), and stream gradient (SL) indices. Active functions in Dezful-Andimeshk can be detected through this study so as to take the precaution of natural disasters such as floods and earthquakes.
Research type
This an empirical research.
Research society, place and time
This research is carried out in the Dezful-Abdimesh basin.
Sampling method and number
Sub-basins and the streams were detected using the Digital elevation model in GIS and divided the studied area into 42 sub-basins.
Used devices&materials
DEM, GIS software, and geological maps were used for the analysis of drainage areas, calculation of geomorphological indices, and detection of geological units, respectively.
Findings by Text
According to the mentioned indices, the findings are presented for each index separately. Analysis of Asymmetry factor index in drainage area: This index was calculated for 42 sub-basins into the studied area (Table 1) and is classified in five classes in terms of tectonic activities (Figure 4). Class 1 shows very high tectonic activity (25.78<Af<38.4), class 2 shows high tectonic activity (16.15<Af<25.78), class 3 shows medium tectonic activity (9.8<Af<16.15), class 4 shows low tectonic activity (4.78<Af<9.8), and class 5 shows very low tectonic activity (0.34<Af<4.78). Analysis of Relative Relief index: The highest and the lowest points of each basin are detected using DEM. The results of this index's calculation are shown in table 1. This index is classified into five classes in terms of tectonic activities (Figure 5). Class 1 shows very high tectonic activity (1605<Bh<2274), class 2 shows high tectonic activity (748<Bh<1605), class 3 shows medium tectonic activity (295<Bh<748), class 4 shows low tectonic activity (130<Bh<295), and class 5 shows very low tectonic activity (46<Bh<130). The maximum height calculated for this index is 2274m in sub-basin9, while its minimum is 46 in sub-basin 27. Analysis of Form factor index: The area and length of each basin are calculated using DEM and form factor was calculated in 42 drainage areas (table 1 and figure 6). This index is classified into five classes in terms of tectonic activities (Figure 5). Class 1 shows very high tectonic activity (0.09<Ff<0.12), class 2 shows high tectonic activity (0.12<Ff<0.17), class 3 shows medium tectonic activity (0.17<Ff<0.24), class 4 shows low tectonic activity (0.24<Ff<0.33), and class 5 shows very low tectonic activity (0.33<Ff<0.46). The range of changes in this index varies from 0.09 to 0.46. Analysis of Hypsometric Integral and curve index: The average, minimum, and maximum height was calculated for each basin using DEM (Table 1). ). This index is classified into five classes in terms of tectonic activities (Figure 5). Class 1 shows very high tectonic activity (0.43<Hi<0.6), class 2 shows high tectonic activity (0.35<Hi<0.43), class 3 shows medium tectonic activity (0.28<Hi<0.35), class 4 shows low tectonic activity (0.22<Hi<0.28), and class 5 shows very low tectonic activity (0.21<Hi<0.22) (figure 7). Hypsometric integral and its curve can be used to recognize the geological situation. The curve in basins 3, 26, and27 with 0.5, 0.51, and 0.6 have the most tectonic activity, respectively (figure8). Analysis of stream length index: The streams' layers were added to ArcGIS for each stream in 42 sub-basins in the studied area and the amount of L and (∆H/∆L) were calculated. The results of these calculations are shown in table1. This index is classified into five classes in terms of tectonic activities (Figure 9). Class 1 shows very high tectonic activity (1054<SL<2017), class 2 shows high tectonic activity (475<SL<1054), class 3 shows medium tectonic activity (245<SL<475), class 4 shows low tectonic activity (93<SL<245), and class 5 shows very low tectonic activity (24<SL<93). Northern sub-basins have a higher value of this index due to the active faults. Analysis of index of active tectonics (Iat) Index of active tectonics is calculated by averaging all mentioned indices including Asymmetry factor, relative relief, form factor, Hypsometric Integral and curve, and stream length gradient for 42 sub-basins located in the studied area (table 1). Hence, the studied area can be classified into four classes in terms of tectonic activities. Class 1 shows very high tectonic activity (1<Iat<1.5), class 2 shows high tectonic activity (1.5<Iat<2), class 3 shows medium tectonic activity (2<Iat<2.5), class 4 shows low tectonic activity (2.5<Iat). Eventually, the map of the distribution of the active tectonics in the studied area was prepared (figure 10). According to this index, the majority of the studied area are classified in classes 1 and 2 of the tectonic activity classes.
Main comparison to the similar studies
The results of Wells et al (1988), Guarnieri & Pirrotta (2008), Figueoroa & Knott (2010), and Melosh & Keller (2013) on tectonic indices using morphometric indices are consistent with the results of the current research.
Suggestions
There is no suggestion reported.
Limitations
There is no limitation reported
Conclusions
The results of the current research show that the recent tectonic activity of the Dezful-Andimesh basin is almost high mainly because of the active faults in this region including mountain forehead fault, Duragh fault, some parts of Balatood fault, Lahbari, and Ramhormoz. The area with high and very high tectonic activity accounts for 70.06%, while the area with medium and low tectonic activity accounts for 27.6% and 2.33%, respectively. The results of the evaluation of morphological indices in the current research approve the recent tectonic activities of this region.
Acknowledgments
None.
Conflict of interest
None.
Ethical Permissions
None.
Funding Sources
None.

TABLES and CHARTS

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