ارزیابی میزان فعالیت گنبدهای نمکی منطقه لارستان با استفاده از شاخص های تکتونیکی و روش سری زمانیSBAS

نوع مقاله: مقاله پژوهشی

نویسندگان

دانشگاه شهید بهشتی

چکیده

گنبدهای نمکی بعنوان یکی از رخدادهای مهم زمین ریخت شناسی ضمن بالاآمدن با حوادث مهمی همراه هستند که مطالعه آن‌ها می‌تواند در درک رخدادهای مانند دیاپیریسم، عملکرد ساختاری، تشکیل مخروط افکنه‌ها مارا یاری دهد. علاوه بر این، گنبدها دارای اهمیت‌های مختلف اقتصادی، گردشگری، علمی و ... هستند که ارزیابی فعالیت‌های آن‌ها در برنامه-ریزی‌ها و فعالیت‌های مختلف علمی بسیار حائز اهمیت است. در این تحقیق پس از شناسایی و مورفومتری گنبدهای نمکی منطقه لارستان، با استفاده از ۹ شاخص دایره‌واری (C)، شاخص برافراشتگی (Bh)، شاخص کشیدگی (Bs)، شاخص انتگرال هیپسومتری (Hi) و مساحت زیر منحنی هیپسومتری (y)، شاخص نسبت انشعاب (BR)، شاخص میانگین طول آبراهه درجه 1 (LN1)، شاخص تراکم زهکشی (Dd) و شاخص فرکانس آبراهه (Fs) به ارزیابی وضعیت فعالیت گنبد‌ها پرداخته شده است و سپس با استفاده از ۲۷ تصویر راداری (از تاریخ ۱۴/۱۰/۲۰۱۴ تا ۲۷/۱۰/۲۰۱۶) و روش سری زمانی SBAS، میزان جابجایی عمودی منطقه محاسبه شده است. نتایج حاصله بیانگر این است که در میزان جابجایی عمودی منطقه علاوه بر حرکت گنبدهای نمکی، عوامل تکتونیکی، ‌فرسایش و فرونشست نیز تاثیرگذار بوده است. در واقع نتایج محاسبه شاخص‌ها حاکی از فعال بودن برخی از گنبدهای نمکی است و نتایج حاصل از روش سری زمانی SBAS‌ نیز بیانگر جابجایی عمودی منطقه و فعال بودن منطقه از نظر تکتونیکی است. اما با توجه به اینکه بعضی از گنبدها نمکی از جمله گنبد چهال که در محاسبه شاخص‌ها دارای امتیاز بالایی بوده ولی در نتیجه حاصله از طریق سری زمانی SBAS‌ در محدوده فرونشست قرار داشته است،

کلیدواژه‌ها


عنوان مقاله [English]

Evaluation of Salt Diapir Activity in Larestan Region Using From tectonic indices and SBAS time series method

نویسندگان [English]

  • Afshan Ghasemi
  • mohammad reza sarvati
  • Shahram Bahrami
  • Bhman Rahimzade
shahid Beheshti university
چکیده [English]

Introduction
Tectonic geomorphology studies the dynamic and dynamic processes involved in shaping the present landscape. In recent years, tectonic geomorphology has been remarkably one of the major and effective tools in detecting active tectonic shapes and seismic hazard maps as well as understanding and understanding the history of the present Earth's surface measurements. Today, tectonics has proven to be an effective application in geomorphological knowledge. Quantitative measurement of landforms allows geomorphologists to investigate the role of active tectonics in landscape deformation. Tectonic geomorphology studies the landforms created by tectonic activity. Quantitative investigation of tectonically active landforms is a very useful tool in reconstructing tectonic history and understanding the evolution of landforms. To study the gradual effects of tectonics over thousands of years, one has to examine the morphological effects that have preserved them. One of the effects that responds to tectonic changes is salt diapir whose form of quantitative features can be influenced by active tectonics. The aim of this study was to identify salt diapir in Fars province and evaluate their activity using different indices. Then, using radar images and radar interferometry, the magnitude of the diapir was increased. Calculate salt and compare it with the results of tectonic indices.

Materials and Methods
This research is based on descriptive-analytical methods. The research data included 1:50000 topographic maps, 1: 100000 geological maps, 30 meters DEM SRTM , Sentinel satellite radar images, and salt diapir morphometric information through field surveys and Google imagery. Research tools include GMT software to map area displacement, ARCGIS to map, Google Inheritance to assess area status, as well as 9 indicators to evaluate salt diapir activity status. The method used in this study is to first use 9 indices Circularity (C), Elevation Index (Bh), Elongation Index (Bs), Hypsometric Integral Index (Hi) and Area Under Hypsometric Curve (y), Branch Ratio Index (BR), Average Class 1 Waterway Index (LN1), Drainage density index (Dd) and waterway frequency index (Fs) The activity status of the salt diapir is investigated and then calculated using the SBAS method of vertical displacement. After calculating different indices to evaluate the activity status of salt diapir and also preparing the vertical displacement rate map, in this step, the relationship between indices and the displacement rate map of the region is discussed.

Discussion and results
In this study, tectonic status of salt diapir was evaluated using different indices. Since the tectonic status of each diapir was different for different indices, salt diapir were rated for each index in order to evaluate the overall diapir for all indices, In fact, scoring has been relative, and given that the diapir has been evaluated in this study, each diapir has a score of 1 to 11 in terms of tectonic status. Evaluation results show that Chalal Salt diapir with average of 7.11, Benako with 6.55 and Aliabad with 6.44 of each index have the highest score and are considered as the most active diapir Salt diapir of Pyramid with average of 5 depleted with 5.22and Nina with 5.44 points are considered as diapir with low tectonic activity. After calculating the indices, the vertical displacement rate of the region was estimated using SBAS time series method. The results indicate that the range of studies over the 2-year period has shifted from -153 to 93 mm. This indicates that the area had a maximum subsidence of 153 mm during the period studied and a maximum of 93 mm uplift.

Conclusion
According to the results obtained by calculating the indices, among the salt diapir, the salt pomegranate has the lowest activity and, as a result of the SBAS method, it is in the area without uplift and subsidence, Corresponds to the results of the indices. But some salt diapir, such as the Chehal Diapir, are considered to be the most active in terms of indicators, While the map shows the extent of displacement in areas without uplift and even subsidence, this indicates the impact of various factors such as groundwater loss, erosion, and etc. In view of the above, it can be said that the study area is affected by salt formations, and in some areas it has been up to 93 mm over the course of 2 years, But due to various factors such as groundwater loss in the southern part of the range, the area has been subdued, so it can be said that the vertical displacement of the area in addition to the salt formations that caused the uplift, groundwater loss and tectonic factors Caused the collapse of the region.
Keywords: Salt diapir, Tectonic indices, SBAS, Larestan

کلیدواژه‌ها [English]

  • salt diapir
  • Tectonic indices
  • SBAS
  • Larestan
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