تحلیل ناهنجاری های شبکه زهکشی و ارتباط آن با تکتونیک فعال در حوضه های آبریز شمال تبریز

نویسندگان

دانشگاه تبریز

چکیده

شبکه های زهکشی فعال ترین و حساس ترین عناصری هستند که می توانند به عنوان ابزاری قدرتمند برای درک فعالیت های نئوتکتونیکی در یک منطقه مورد استفاده قرار گیرند. به منظور تحلیل اثرات تکتونیک فعال در حوضه­های زهکشی از تحلیل­های مورفومتری که ابزار مفیدی در مطالعات تکتونیکی محسوب می­شوند، استفاده می­شود. در این پژوهش تاثیر فعالیت های تکتونیکی گسل تبریز  بر حوضه های آبریز ورکش چای، گمانج چای، نهند چای و سرند چای واقع در شمال تبریز با استفاده از شاخص های تراکم زهکشی(Dd)، فرکانس زهکشی(Df)، ضریب گردواری(CR)، نسبت طول آبراهه اصلی به متوسط عرض حوضه (LSBW)، حجم به سطح حوضه (VA)، نسبت کشیدگی(Re)، شاخص انشعاب(R)، شاخص عدم تقارن حوضه زهکشی (AF)، نسبت شکل حوضه (BS) و شاخص تعقر لانگبین(IC)، شاخص ناهنجاری های سلسله مراتبی (Da) و شاخص تراکم ناهنجاری های سلسله مراتبی(ga) بررسی شدند. بین شاخص­های مذکور رابطه  همبستگی پیرسون برقرار شد و ضریب تببین بدست آمد. نتایج  نشان داد که ضریب  همبستگی بین پارامتر هایDa-Re, Da-CR, Da-Bs, Da-LSBW, Da-R, Da-IC, به ترتیب 99/0، 91/0، 69/0، 87/0- ،85/0-، 55/0 است و بین پارامترهای ga-Re ga-CR, ga-Bs ,ga-LSBW, ga-R, ga-IC, ضریب همبستگی  به ترتیب 95/0، 93/0، 83/0، 94/0-،80/0- ، 65/0 برقرار است. نتیجه تحلیل ها نشان می دهد که شاخص های Da وga کاملا تحت تاثیر کشیدگی حوضه ها که ناشی از اثر تکتونیک فعال می باشد قرار دارند. در ضمن ناهنجاری های شبکه زهکشی تمامی حوضه های شمال تبریز از شاخص تقعر نیمرخ رودخانه نیز متاثر می شوند.

کلیدواژه‌ها


عنوان مقاله [English]

Analyzing the Drainage Networks Anomalies and its relation with Active Tectonics in the Basin of Northern Tabriz

چکیده [English]

Introduction
     Tectonic activity plays an important role in the development of drainage basin morphology.  Drainage networks are the most active and sensitive elements which can be used as a powerful tool to understand the neotectonic activities of an area (Ahmed and Rao, 2016). The geomorphic indices are a tool for analyzing the landforms and evaluating the degree of tectonic activity in a given area (Keller, 1986; Guarnieri and Pirrotta, 2008). Calculation of parameters of the hierarchy of the hydrographic network such as bifurcation index (R), bifurcation ratio (Rb), hierarchical anomaly number (Ha),hierarchical anomaly index (Δa), drainage density (Dd) and drainage frequency (Df), allows us to define the influence of tectonics on the hydrographic network evolution (Guarnieri and Pirrotta, 2008). Several studies show that rivers necessarily flow from high to low elevations parallel to the maximum regional slope (regional topographic gradient). All deviations of stream flow direction from the regional topographic gradient Considered as anomalies related either to structural or lithological discontinuities (Deffonataines, 1990; Sedrette et al, 2016). Iran is located in an active tectonic zone due to its location in the belt of the Alp-Himalayan. Arabia and Eurasia shells convergence is the cause of active tectonic in Iran. There is a special complication of structure process on northwest of Iran. One of Azarbijan important faults that plays basic role in its structure evolution is Tabriz fault. It crosses the north of Tabriz city . North of Tabriz Fault (NTF) is collection of fault branches. This fault affects upon geology and geomorphology processes on region basins. Since drainage  networks  patterns present useful information about past and present  region tectonic, so one of sensitive landforms to tectonic activities are rivers. In this way, the present study studies the effect of active tectonics of Tabriz fault on the hierarchical anomalies of the drainage network Varkesh Chay basin,  Gamanaj Chay basin,  Nahand Chay basin  and  Sarand Chay basin that located on north of Tabriz.
 
Methodology

In this research for recognizing study region we have used  from topography maps, geology maps 1:100000 ( Tabriz and Khoja) and DEM image with resolution of 30 meter. Also ARC GIS, EXCEL and SPSS soft wares were used for  drawing region maps and parameter analysis. In this research studied Varkesh Chay basin,  Gamanaj Chay basin,  Nahand Chay basin  and  Sarand Chay basin that located on north of Tabriz.  In this study used a quantitative method for calculation of stream's hierarchical anomaly number. Morphometric parameters  to be used are hierarchal anomaly index (Δa), Density hierarchical anomaly index (ga), asymmetry factor (Af), basin Shape (Bs), basin length to mean width ratio (Bl/Bmw), bifurcation index (R), drainage density (Dd), drainage frequency (Df), Basin volume / Area index (VA), Basin elongation ratio index (Re), Circulatory ratio (CR) and Langbin Concavity index (IC).
 
 
Results and Discussion
Results show that the strong correlations exist between pairs Da-Re (R=0.99), Da-IC(R=0.91), Da-LSBW (R=-0.87), Da-BS (R=-0.87), Da-R(R=0.69), Da-CR (R=0.55). also the strong correlations exist between pairs ga-IC(R=0.95), ga-Re (R=0.93), ga-R(R=0.83), ga-LSBW(R=-0.94), ga-CR(R=0.65), ga-BS (R=-0.8). The results of the analyzes indicate that the indices Δa and ga are completely affected by the basins elongation caused by the active tectonic effect. In addition, Anomalies in drainage network of all northern basin of Tabriz are affected by the Langbin Concavity index (table1).
 
Table 1: Coefficients Pearson Correlation between morphometric index  in study basins



IC
Df
Dd
R
VA
LSBW
CR
Af
BS
Re
 


0.91
0.06
0.02
0.69
0.08-
-0.87
0.55
0.33
0.85-
o.99
Da


0.93
0.27
0.14
0.83
-0.27
-0.94
0.65
0.25
-0.80
0.95
ga



 
 
Conclusion
 
In this study used a quantitative method for calculation of stream's hierarchical anomaly number. Morphometric parameters to be used are hierarchal anomaly index (Δa), Density hierarchical anomaly index (ga), asymmetry factor (Af), basin Shape (Bs), basin length to mean width ratio (Bl/Bmw), bifurcation index (R), drainage density (Dd), drainage frequency (Df), Basin voulume / Area index (VA), Basin elongation ratio index (Re), Circulatory ratio (CR)  and Langbin Concavity index (IC) . Results show that the strong correlations exist between pairs  Da-Re (R=0.99), Da-IC(R=0.91), Da-LSBW (R=-0.87), Da-BS(R=-0.87), Da-R(R=0.69),  Da-CR (R=0.55). also the strongcorrelations exist between pairs ga-IC(R=0.95), ga-Re (R=0.93), ga-R(R=0.83), ga-LSBW(R=-0.94), ga-CR(R=0.65), ga-BS(R=-08). The results of the analyzes indicate that the indices Δa and ga are completely affected by the basins elongation caused by the active tectonic effect. In addition, Anomalies  in drainage network of all northern basin of Tabriz are affected by the Langbin Concavity index.

کلیدواژه‌ها [English]

  • Hierarchal Anomaly
  • Drainage Networks
  • Morphometric Parameters
  • Geomorphic index
  • Active Tectonic
  • North of Tabriz Basins
  • North of Tabriz Fault (NTF)