Remote Sensing (RS)
Mohamad Fathollahzadeh; Mojtaba Yamani; Abolghasem Goorabi; Mehran Maghsoudi; Mernoosh Ghadimi
Abstract
Extended Abstract
Introduction:
The landforms created by tectonic processes are studied by morphotectonics, in other words, morphotectonics is the science of applying geomorphic principles in solving tectonic problems. Quantitative landscape measurements are usually based on the calculation of geomorphic ...
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Extended Abstract
Introduction:
The landforms created by tectonic processes are studied by morphotectonics, in other words, morphotectonics is the science of applying geomorphic principles in solving tectonic problems. Quantitative landscape measurements are usually based on the calculation of geomorphic indices, using topographic maps, satellite images aerial photographs, and field visits. Coastal deltas are part of landforms and landscapes that, due to the proximity of two environments, land, and water, leave visible effects against tectonic activities, such as changing the pattern and location of deltas due to the change in the course of coastal rivers, the formation of unbalanced coastal terraces in parts of the coast, and the emergence of cut beaches in the form of seawalls.
One of the methods of identifying and measuring land changes is using radar remote sensing. The principles of this technique were first described by Graham in 1974 (Pacheco et al., 2006). Interferometry using radar images with an artificial window or SAR is a precise method based on the use of at least two radar images of the same area, which measures the height displacement changes in wide areas and during different time intervals with a significant accuracy of millimeters (Dong et al., 2018).
The coastal areas of northern Iran are of great importance due to the high population density and the ability to grow and develop economically and agriculturally, so monitoring geomorphic changes in the direction of sustainable development of these areas is particularly important.
In this research, the eastern coast of the Caspian Sea from Gomishan to Joibar is investigated in terms of subsidence and uplift using radar remote sensing techniques to determine the active tectonic zones of the coast in terms of temporal and spatial changes.
Materials and Methods:
The Eastern Caspian Plain is the border between the Caspian Sea and West Gorgan and includes the cities of Gomishan, Bandare Turkman, Bandare Gaz, Gulugah, Khazarabad, and Joybar. The absolute height of the Caspian Plain along the coastline is determined according to the sea level, based on the hydrographic data of the Baku station, since 1850, the Caspian sea level has varied between -25.4 and -29.4 (Abdolhi Kakrodi, 2012).
The history of seismic activity in North Alborz shows that cities like Rasht, Lahijan, Amol, and Gorgan, have been destroyed many times due to destructive earthquakes (Aqhanbati, 2013). The Alborz fault is an active fault that is stretched in a clockwise direction in the southern Caspian basin.
In this research, according to the desired goals and radar remote sensing techniques, a series of Sentinel-1 radar images with a suitable time and space difference (maximum 30 days and maximum 150 meters respectively) including 61 images in time from 2014 to 2021 were prepared and processed.
Results:
The results obtained from the SBAS model indicate that the eastern part of the Caspian coast is more affected by the uplift and this trend continues up to Gorgan Bay. The Gorgan city has an uplift between 20 and 40 mm/year, which is reversed towards the coastal area, and subsidence of 10 to 52 mm/year occurs, which decreases as it approaches the coast and reaches 10 mm /year.
Discussion, Conclusion:
According to the results obtained from radar interferometry, the eastern coast of the Caspian Sea is more affected by uplifting. The Gorgan city has an uplift between 20 and 40 mm/year, which is reversed towards the coastal area, and subsidence of 10 to 52 mm/year occurs, which decreases as it approaches the coast and reaches 10 mm/year.
To verify the results obtained, the data of the Gorgan geodynamic station was used, which shows subsidence of about 90 to 100 mm in a 6-year period, which is consistent with the values obtained from radar interferometry Based on comments Shahpasandzadeh (2013) and the reports of Nazari et al (2021), active tectonics caused by the Caspian fault that indicates the horizontal geodynamic displacement diagram of Gorgan, the small area towards the north and east during this time, which is observed in the form of numerous branches with a thrust (reverse) mechanism and a right-slip component with a slope to the south in Golestan province.
Considering that the main feature of the coast of the Caspian Sea is the Surface rivers and the use of groundwater is very little and also the extraction of gas, oil, and mining resources, which is another factor in the occurrence of land subsidence, does not exist in this area, and there isn’t also huge and heavy structure in the study area that affects the subsidence of the surface; so displacement in the study area is the result of active tectonics.
Mojtaba Yamani; Arefeh Shabanieraghi; Seyed Mohammad Zamanzadeh; Abolghasem Goorabi; Nafiseh Ashtari
Abstract
Extended Abstract
Introduction
Climate changesare considered to be the most important event of the Quaternary period largely reflected in the geomorphology and sedimentology of the period.Paleogeomorphology helps us to understand past climate changes and predict future changes. Depending on the ...
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Extended Abstract
Introduction
Climate changesare considered to be the most important event of the Quaternary period largely reflected in the geomorphology and sedimentology of the period.Paleogeomorphology helps us to understand past climate changes and predict future changes. Depending on the Quaternary periods, closed pitlakes are called cold or rainy period lakes.Some of these lakes have completely dried up, others are temporary lakes that change into playas in the dry season, and others have been larger in the past. Researchers can identify pluvial lakes in today’s arid regions, because of the variety of factors and complex processes involved in their formation.Mighan Playa is located in the central and southwestern areas of Markazi province. It includes seasonal and saline Tozlogol Lake, and alluvial plains.
Methodology
The present study used evidences of playa lake sediments as well as geomorphological evidences(lake terrace) to investigate the extent of MighanLake in Quaternary period. Data included datacollectedfrom library sources, statistical data, field surveys, sedimentary samples, sedimentary evidences, climatic data, remote sensing data received from Landsat TM satellite, ETM, and SRTM digital elevation models(SRTM 90 meters, and Dem10 meters).Initially, previous studies and environmental characteristics of the area were analyzed. Then, lake terracewas investigated to find geomorphic evidences of Pluvial Lakes in Quaternary period. To do so, probable ranges of the lake Terrace were determined using satellite imagery, geological maps, and elevation data of digital models. Probable area was divided into several distinct zones, and finally an area was identified in the western part of the lake and based on the elevation of this zone, the extent of the lake catchment in Quaternary period was determined. During fieldwork, samples were collected from the mountain slope line toward the Playa and lake shore, and then granulometrytests were performed on the 14 collected samples to determine the amount and type of sediments.Sedimentary and graphical analysis were also performed based on Folk classification. The percentage of clay and sand in the new samples collected from the region containing this mountainous area, lake coast and deeper parts of the lake were determined and attributed to past sediments. In this way, the information could be used to determine the extension of lake sedimentsin the past.Based on sedimentary logs (Arak Groundwater Studies Report, Central Water department of Markzani Province), sedimentology studies and percentages (clay-sand-gravel) of present-day samples collected from deep sections of Playa andelevated areas of sediment pits were interpolated in GIS environment and a map of the lake extension in the Mighan catchment areawas prepared.Subsequently based onpaleogeographic studies, paleontological climate of the area and sedimentation rate calculated by Pedrami in 1993, a map was produced to show the extent of sediments and the lake progressions and regressions in the past.
Discussion
The stratigraphic and sedimentary evidences of logs in the margins of Mighanpit indicates changes in wet and dry periods. Type and size of sediments reflect the climatic conditions in each period, while high percentage of clay sediments reflects lake conditions. Paleontological sedimentological maps of the area show that the clay sediments were more concentrated in the southwestern, western and northwestern regions. Uplift of the Talkhab fault in the northeastern regionhas resulted in tectonic asymmetry of the pitand concentration of sediments in the western and southern parts. According to Krinsley, Bubeck, Pedrami and etc. Lake Mighan has been larger in the past. However, none of these researchers have determined the extent of lake water in the past. In this study, the extent of the lake was determined by reconstruction of clay sediments and using geomorphological evidencescollected from the lake shorelines (lake terrace) near Mighan village (Mashhad). Results indicated a height of 15 m in Quaternary period.
Conclusion
Sedimentary and geomorphologic evidences indicated that compared to the present playa level, the Lake fluvial was more permanent and vast in the past, but this extension differs in different directions and shows significant differences due to the tectonic location of the area.