مخاطرات طبیعی همه‌ساله خسارات زیان‌باری را در سراسر جهان و از جمله ایران بوجود می‌آورد. حوزه وارک واقع در استان لرستان به دلیل خصوصیات متنوع زمین‌شناسی نظیر لیتولوژی، تکتونیک و شرایط خاص آب و هوایی، از جمله مناطق دارای پتانسیل مخاطرات زیست‌محیطی است. برای کاهش خسارات ناشی از این مخاطرات، اولین و مهم‌ترین کار تعیین مناطق با پتانسیل بالای خطر است. به منظور بررسی مخاطرات زیست‌محیطی در این حوزه ابتدا هر یک از لایه‌های اطلاعاتی با استفاده از تصاویر ماهواره‌ای +ETM (سال 95)، نقشه زمین‌شناسی، نقشه توپوگرافی و بازدیدهای میدانی (سال 96) شناسایی و ثبت گردیدند. سپس با استفاده از لایه‌های اطلاعاتی شیب، جهت شیب، ارتفاع، کاربری اراضی، زمین‌شناسی، کانون زمین‌لرزه‌ها، گسل، شبکه آبراهه و بارش در محیط نرم‌افزار ArcMap و بر اساس روش تلفیقی سلسله مراتبی فازی نقشه مخاطرات زمین‌لغزش، سیل، فرسایش و زمین‌لرزه تهیه شده است. در این تحقیق، به منظور تهیه نقشه نهایی مخاطرات زیست‌محیطی، با استفاده از قضاوت کارشناسی مخاطرات چهارگانه منطقه وزن‌دهی و سپس هم‌پوشانی گردید. بر اساس نتایج به دست آمده به ترتیب 03/9، 84/20، 68/27، 41/27 و 03/15 درصد از مساحت منطقه در کلاس‌های خطر خیلی کم، کم، متوسط، زیاد و خیلی زیاد قرار دارد. همچنین نتایج بررسی نقشه مخاطرات زیست‌محیطی منطقه نشان می‌دهد که به ترتیب زمین‌لغزش و سیلاب از نقش پررنگ‌تری در ایجاد پهنه‌های با خطر بالا برخوردار می‌باشند. Manuscript profile

Dasht-e-Arjan is a northeast trending graben located 65 km west of Shiraz. It was formed along active segments of the Korrehbas fault, perpendicularly to the Shahnesh in and Salamati anticlines. Oriented sampling from bordering fault planes and striations was carried out to evaluate the relative amounts of paleostress/strain needed to form the graben. Measurements of e-twins and c-axis of calcite properties on XY and XZ planes, using five universal stages in a polarizing optical microscope, showed the presence of type I and II calcites. Because the calcite e-twins and fault striations register the last deformation phase, measurements of calcite e-twins show the plane strain K=1 in the last graben deformation phase. The inversion method, applied for the analysis of fault striation data, showed a plane stress ellipse (φ=1), (σ1=σ2), and a plane strain ellipse (r0=1). The mean orientation of the sub-vertical maximum principal-stress (σ1) was N23°.70°E, and the mean orientation of minimum principal-stress (σ3) was S58°.26°E. Based on the analysis of twinned calcite crystals, the mean direction of the determined compression and tension were S55°E ± 9.−32° and N35°E±11.−72°, respectively. Using multiple inversion methods, and based on the investigation of fault striation data, we can expect two stress phases. The paleostress phase, acting as a tensional regime, caused the formation of SW trending faults, while the recent phase caused the formation of new fractures within the study area. Based on field and laboratory analyses, it is suggested that a tension tectonic regime is dominant in the studied graben. Manuscript profile

One of the methods for dealing with the problem of water shortage and the decline of groundwater levels in the arid areas is the construction of underground dams. It is difficult to make a decision about suitable locations for the construction of underground dams because of the necessity to consider numerous factors. Some of these criteria are hydrological, geological and geomorphologic characteristics of the area. By applying the GIS and AHP methods, this study attempted to introduce the suitable locations for construction of underground dams in Roomeshgan area in Lorestan Province, Iran. For this purpose, factors such as slope, lithology, land use, alluvium thickness, water quality, and distance from the well, fault and stream and rivers network were used. Using the Analytic Hierarchy Process (AHP) for the possibility of considering various qualitative and quantitative criteria, the process can be one way to select the appropriate location for constructing an underground dam. In this study, after the assessment of the used layers in the Expert Choice software, weight mapping of each layer was prepared. Then, the map of suitable areas for construction of the underground dam was prepared by overlapping the weight mappings of each layer in ArcGIS software. According to the results, 15.87 %, 11.96 %, 35.75 %, 33.23 % and 3.18 % of the region are located in very poor, poor, moderate, suitable and very suitable areas, respectively. After several field surveys of the area with three percent, six locations were selected for underground dam construction. The results show that the factors mentioned above have the most important role in locating the underground dam construction and the chosen method has high accuracy. Manuscript profile