نوع مقاله : مقاله پژوهشی

نویسندگان

1 گروه زمین شناسی، دانشگاه بیرجند، بیرجند، ایران

2 پژوهشکده علوم زمین، سازمان زمین شناسی و اکتشافات معدنی کشور، تهران، ایران

چکیده

گسل دورود به عنوان یکی از مهم­ترین قطعات لرزه­زای گسل اصلی جوان زاگرس از نزدیکی منطقه ارجنگ در یک روند شمال‌باختری–جنوب‌خاوری تا بروجرد در طول  امتداد یافته است. منطقه مورد بررسی بعنوان قطعه دوم از گسل دورود بین َ10 °33 تا َ25 °33 درجه عرض شمالی وَ05 °49 تا َ25 °49 درجه طول خاوری واقع شده است.در این پژوهش بررسی‌های دقیق ریخت‌زمین‌ساختی به روش نزدیک میدان انجام گرفت و با انجام پیمایش به روش RTK توسط دستگاه GPS کینماتیک، مدل ارتفاعی رقومی و نقشه توپوگرافی رقومی با دقت بالا از سطح گسیختگی‌های تهیه شده، جابجایی‌های محاسبه شده برای 3 ایستگاه به ترتیب: جابجایی تجمعی افقی روی سطح گسل 59/21، 05/10 و 94/13، جابجایی تجمعی قائم روی سطح گسل 58/6، 57/5 و 47/13 و جابجایی تجمعی خالص 58/22، 49/11 و 40/19 بدست آمد. به منظور بررسی سازوکار گسل زاویه ریک گسل محاسبه گردید به ترتیب: °17،°29 و °44 است براساس نتایج بدست آمده گسل دارای مولفه شیب‌لغز می‌باشد. همچنین در مطالعات ژئوفیزیک به روش مقاومت‌ویژه با آرایش دوقطبی(دایپل- دایپل) دو نیمرخ مورد استفاده قرار گرفت سپس پرداز نهایی و مدل‌سازی داده‌های مقاومت ویژه در نرم‌افزار Res2dinv انجام گرفت. در ادامه پیمایش مغناطیس‌سنجی سزیم بر روی 4 مقطع 160 متری صورت گرفت. پس از اتمام عملیات و برداشت داده‌ها و پردازش نهایی داده ها تفسیر واضح‌تری از ساختارهای زیر‌سطحی به خصوص گسلش و ناپیوستگی در منطقه مورد مطالعه به دست آمد. گسل دورود در این محدوده گسل 3شاخه بوده، که گسل شاخه F4 به‌عنوان گسل اصلی دورود و مابقی شاخه‌های گسلی به موازات آن می‌باشند.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

Using GPS RTK data and geophysical data in determine rate tectonics activity and identify trace second segment Dorud Quaternary fault (Southwestern Iran)

نویسندگان [English]

  • Zahra Kamali 1
  • Mahmoud Reza Heyhat 1
  • Hamid Nazari 2
  • Mohammad Mahdi Khatib 1

1 Department of Geology, Birjand University, Birjand, Iran

2 پژوهشکده علوم زمین، سازمان زمین شناسی و اکتشافات معدنی کشور، تهران، ایران

چکیده [English]

The Zagros range extends for 1500 km from southeastern Turkey to Hormuz Strait and Persian Gulf. This active fold and thrust belt is composed of deformed sediments of the Arabian margin and has grown since Early-Middle Eocene in response to convergence and ongoing collision between Arabia and Eurasia plates. Crustal shortening in the Zagros is expressed by active folding and thrusting associated with a widely distributed shallow seismicity (depth < 20 km). The Dorud fault with general trend of NW-SE has known as one of the most important seismic in segments of Zagros Main Recent fault, near the Arjng area.In this study we use morphotectonic evidences to show that seismic behavior of this fault in the past has a clustering model in some time intervals. Geomorphic indicators are used as a tool to identify recent structures and movements. However, prior study of the region and the presence of high magnitude earthquakes that destroyed 100% of the villages with a 1 meter vertical displacement of the area indicate high tectonic activity. For this purpose at the first near-field morphotectonical analysis performed using Real Time Kinematics (RTK) GPS survey, digital elevation model and digital topographic map with high accuracy of surface ruptures of past earthquake prepared. To calculate the amount of displacement on the fault plane after applying the software steps on the DEM in Surfer software, perpendicular to the strike of the fault. These two lines extend the tangent to break the fault. The distance between the two points that cut two tangent lines indicates the amount of vertical displacement on the earth's surface. Digital elevation model and digital topographic map with high accuracy from the level of ruptures created from these findings were used to determine the quaternary fault of Dorud. Also, the geophysical studies of this part of the Dorud Fault after the preliminary studies of geology and the investigation of the probable extension of the fault using a special bipolar resistivity method (bipolar- bipolar) with a profile of 10 meters in 10 meters of two profiles were used. After the final processing and modeling the resilience data in Res2dinv software, the cesium magnetometric scanning was carried out on 4, 160-meter profiles.  According the results calculated for 3 stations amounts displacement respectively: The horizontal cumulative displacement on the fault surface is 21.59, 10.05, and 13.94, the vertical displacement of the vertical side on the fault surface is calculated 58.6, 57.5 and 13.47 and the net cumulative displacement is measured 22.88, 11.49 and 40/19. In order to investigate the fault mechanisms, the rake angles were calculated of the fault respectively as 17, 29 and 44 degrees. According to the results, the fault has a dip- slip component. Geoelectric impressions using a bipolar and bipolar arrangement on 2 the highest for the apparent resistivity of 101.7 and the least value 7.2 mm. Geo-electric resistivity measurements with CRP arrangement with the characteristics of OA = 50m and MN = 20m included two profiles with 70 points and a total of 145 points. In order to determine the lateral changes of the ground resistance, CRP resistivity measurements with OA = 50m and MN = 20m profiles on 0 profiles containing 33 points and profiles 80 including 37 points were performed, the highest value for the specific strength of 135 the least value is 13 ohm-meter. Investigation was done by magnetization on four profiles of 0, 40, 80 and 100 consecutive (Continue) with linear 0.64m. Geophysical studies on faults Dorud, the resistivity data acquisition with dipole-dipole array and 10 and 10 meter electrode spacing. After final data processing and inversion of resistivity data in Res2dinv software, cesium magnetometery survey on 4 profiles 160 metric. After the completion of field operations and data question clearer interpretation of the subsurface structures, especially faults and discontinuities in the study area were obtained. The Dorud fault in this site is characterized by three fault lines, which is to say that the F'4 fault, according to morphotectonic studies, has been made as the main Drood fault and the rest as faults parallel to it.There are three possible fault symbols F'3, F'4 and F'5 in the region showed that there can be prepared a series of fault according to the geological map of the studied area is confirmed. The main fault as the fault F'4 Dorud and other faults are parallel to it. All branches of the fault are partly in parallel with stepped-up right and left Stairs in some places just to releasing bend small landslides were observed in the region and in the region just too restraining bend with compression strike- slip duplex.

کلیدواژه‌ها [English]

  • Dorud fault
  • Kinematics GPS
  • Main Recent fault Zagros
  • Resistivity
  • Cesium Magnetometry