پديد آورندگان :
شريفي كيا، محمد نويسنده دانشگاه تربيت مدرس, , , افضلي، عباسعلي نويسنده كارشناس ارشد ژيومورفولوژي، دانشگاه تربيت مدرس , , شايان، سياوش نويسنده ,
كليدواژه :
ژيومورفولوژي كاربردي , عوارض مورفولوژيك , تداخل سنجي تفاضلي راداري , فرونشست , دشت دامغان
چكيده فارسي :
فرونشست زمين به‌عنوان پديدهاي مورفولوژيك است و ظهور طيف وسيعي از عوارض مورفولوژيك پيامد از آن همانند ايجاد درز و ترك در سازه‌ها؛ تغيير در شكل و هندسه سطحي زمين ازجمله عمومي‌ترين رخنمون‌هاي قابل‌رويت ناشي از فرونشست است. پديدهاي مورفولوژيك ناشي از رخداد فرونشست به سبب فراگيري فضايي و همچنين حدوث كند و بطيي آن در عين خسارت‌بار بودن؛ وجوه خارجي چندان مشخصي نداشته و به سهولت قابليت شناسايي و درك ندارد. از همين رو در اين تحقيق به‌منظور يافتن الگوي فرونشيني زمين در دشت دامغان، ابتدا نرخ و دامنه فرونشست، طي دوره‌هاي زماني 6 ماهه و 1 ساله با بهره‌گيري از داده‌هاي راداري دو سنجنده ASAR و PalSAR به كمك تكنيك تداخل سنجي تفاضلي راداري استخراج شد كه نتايج حاكي از حدوث فرونشستي سالانه 14 سانتيمتر بوده است. به‌منظور استخراج اثرات پديده‌هاي ژيومورفولوژيك ناشي از فرونشست، هسته‌هاي در حال فرونشست با نرخ و دامنه فضايي آن از طريق تداخل‌نگارهاي توليدي استخراج شد. همچنين براي درك بهينه ظهور پديده‌هاي ژيومورفولوژيك؛ عوارض سطحي به سه دسته سطح، خط و نقطه تقسيم و بسته به الگوي فضايي تاثيرگذاري فرونشيني، از هسته تا لبه‌ها؛ نقاط كنترل زميني در هريك از اين دسته‌ها بر روي تصاوير انتخاب و اقدام به پي‌جويي آن‌ها در سطح محدوده گرديد. نتايج حاصل از اين پيمايش، مويد شناسايي و ثبت عوارضي چون گسيختگي‌هاي طولي (عمدتاً در لبه‌ها و مرز هسته‌هاي فرونشست)؛ فرونشيني شعاعي و ايجاد فروچاله بخصوص در مسير قنوات؛ و دگرگون شدن چاه‌هاي بهره‌برداري مي‌باشد. تواماً قرار‌گيري تاسيساتي چون راه‌ها، خط آهن و قنوات و همچنين مساكن در طول اين گسيختگي‌ها رويت؛ و تغييرات ثبت شد؛ و عقيم شدن اراضي زراعي و كاهش ظرفيت آبخوان دشت به‌عنوان اثرات محيطي فرونشست معرفي گرديد.
چكيده لاتين :
Introduction Land subsidence is a morphological phenomenon that its extraction and assessment requires precision tools with regionally broad applicability. Occuracies of this feature can be based on natural and humane causes such as tectonic and water withdrawal. Subsidence can affects manmade surface (roads, railway, Houses and…) and subsurface infrastructures (Pipelines, wells, qanats and …). Because of subsidence slow rate, evaluate and assessment of its affects requires precision tools with regionally broad applicability. Based on climatic and geologic condition, subsidence almost accurse in dry plains with unconsolidated sediments. Damghan plain placed on south of Alborz range and north of Hajaligholi Kavir face with subsidence and its effects. Methodology To access the land subsidence effects on Damghan plain, at first subsidence rate and distribution during 6 and 12 months based on SAR data (Asar and Palsar), using D-InSAR technique obtained. Morphological phenomena and features extraction was next step in this study. Thus subsidence area divided to boundaries and centers. Boundaries contain lowest and centers contain highest subsidence rates. Feature extraction based on manmade infrastructure in shape of point, line and polygon. Therefore ground control points selected relate to rang of subsidence and infrastructures. To follow this ground control points on study area a GPS device were used and 29 ground control points checked. Because of different subsidence rate in boundary and center of subsided area and occurrence of almost of subsidence affects between boundary and center, we move from boundary to center. After achieve, features evaluate and Destruction and change rate, recorded. Results and discussion SAR data (ASAR & PalSAR) processing ,respectively represented 7 and 14 centimeters value of land subsidence. In order to extract the geomorphologic effects of subsidence, we surveyed subsided area by deferential interfrograme extraction and surficial features and divided them into points, lines and polygons based on types of subsidence affects on center and boundary of subsided area , also we selected ground control points and investigated. Totally 23 ground control points selected. Based on field work, results represented that longitudinal cracks located in boundary of differential subsided pieces and affected infrastructures and building such as roads, railways, qanats and houses. And appeared that in relate to features type as point, line and polygon , effects were different. Point shape infrastructure this infrastructure indicates surface and subsurface point shape infrastructure. For example Street lighting indicates surface and wells indicate subsurface point shape infrastructures. Results was shown street lighting and wells affected by subsidence. Wells instruments were destroyed and affected water discharge .linear shape is other type of infrastructures that include of roads and railways and pipelines. This infrastructures because of themes shape ,direction and material, differentially affected. For example railway do not fragmented but bended. And third shape of infrastructure include polygonal shape same as houses, bridges, farms and factories. These infrastructures depend of themes location in subsidence area, in boundaries and center, differentially affected. In boundaries subsidence result in vertically fragments and horizontal cracks include center of subsided area. But subsidence effects don’t terminated to buildings and structures also in subsided area, Results show that environmental effects of land subsidence includes barrenness of agricultural land and aquifer compaction. barrenness of agricultural land result in cracks in farm land that causes water, time and money wasting. And Aquifer compaction can causes permanent loss of aquifer capacity. Conclusion The central part of Damghan plain annually subsiding 14 cm that often include farm lands and rural settlements, and urban houses located in boundaries of subsidence area. Subsidence occurrence in this region with a group of construction, agriculture and settlement infrastructures prepared this area to appearance morphological features that relate to buildings and infrastructures in shape of point, line and polygon. Point shape same as wells, street lighting and qanat, linear structures same as roads, railway and pipelines, and polygonal infrastructures such as houses, bridges, farms, factories and manufactories. Modulation of data analysis and field data obtained appropriate condition to feature extraction. Research results specified that the most appropriate method to extract this features is movement of boundaries to core of subsidence area in this region and any similar region. And in environmental effects of subsidence specified rhate because of short period of SAR data, only attend to aquifer compaction and other environmental effects because of long occurrence period (more than one years) don’t explored.
