Seismotectonics of Al-Refaei District and Surrounding Areas from Seismological and Geophysical Data Southern Iraq

الموضوعات

علوم بحتة وطبيعية

الملخص

Al-Refaei district is one of the largest towns in the Thi-Qar governorate in southern Iraq. Tectonically, it is located in the central Mesopotamian Plain of the Arabian plate. For the last two decades, this area and surrounding cities such as Al-Neser, Qalat Suker, Al-Fajer, and Al-Hay experienced several small to moderate-size earthquakes that seem to be clustered in a relatively small area. Seven high-frequency seismic stations were installed in Al-Refaeicity to monitor the seismic activity of the study area for the period 2014 to 2018.These stations formed a network called Al-Refaei seismic Array. Additionally, broadband seismic stations were installed in different cities in Iraq as part of the Iraqi Seismic Observatory (ISO) and used in this study. During the period of monitoring, more than 56 earth quakes were recorded, and 35 of them were detected by the high-frequency stations, and not reported by any local or international seismic observatories. The Computer Programs in Seismology (CPS) was used mainly in conducting most of the data analyses in this study. The crustal structure of this area was estimated to understand the geological and tectonic setting and to conduct the relocation of recorded earthquakes. Three techniques were used for this purpose. First, the inversion of P-wave receiver functions (RFs)was applied to derive the Moho depth and sedimentary thickness using data from the NSR1broadband seismic station. Second, the cross-correlation of ambient seismic noise was applied to estimate a detailed velocity model for the sedimentary cover using data from three broadband seismic stations; these are NSR1, NSR2, and NSR3. Third, the joint inversion of P-wave receiver functions and Rayleigh wave dispersion curves was applied to obtain an accurate velocity model of the sedimentary cover. The results show that the crustal structure in the study area has three distinct discontinuities. The first is the discontinuity within the sedimentary column with a thickness around 4km (Vs 2.44km/s); the second isthe basement rocks with a depth of 12km (Vs 3.17km/s), and the third isthe Moho discontinuity with a depth of 46km (Vs 3.87km/s). Thus, the sedimentary thickness in the study area is around 12kmand the continental crust is around 34km. The derived velocity model, which is called in here Al-Refaei (REF1),was used to relocate earthquakes that occurred in the study area. Data from the high-frequency and broadband seismic stations were analyzed by Geiger’s least-squares method to determine accurate earthquake locations. The results of earthquake relocations depict two seismic zones in the study area. The first zone is located in Al-Hay city with attend of NW. This seismic activity might be related to the Ramadi-Musaiyib longitudinal fault. The second zone is located in Al-Refaei city with a trend of NW, which is not related to any known or studied fault. Therefore, geophysical data were analyzed using Petrel software to detect the fault that can be responsible for the seismic activity in this zone. The results confirm the existence of a fault with the direction of NW that we called Al-Refaei. The integration between the seismological and 3D seismic data reveals that the Al-Refaei fault is an active reverse fault with S62 ̊E strike direction and 43 ̊ dip angle. Al-Refaei fault is located within Al-Gharrafoilfield. Due to the production history and drilling activities of the oilfield, the study suggests that the reason behind the seismicity of the Al-Refaei fault might be related to the Al-Gharraf oilfield, which means the seismic activity of the Al-Refaei fault might be induced or man-made

روابط وملفات

التعريف والنوع

رقم الوثيقة

0e72feba-1e06-4951-af31-17c1a059dce3

رقم العقد

0

نوع الوسائط

Crawler

نوع المحتوى

الرسائل العلمية

صيغة المصدر

رسائل دكتوراة

نوع الملف

pdf image

أسماء الملفات

0e72feba-1e06-4951-af31-17c1a059dce3_1.pdf

بيانات النشر

ألقاب المؤلفين

[{"name_ar":" Wathiq Ghazi Abdulnaby","title_ar":"اشراف","title_en":"Supervision"},{"name_ar":"Ali Ramthan Hussein","title_ar":"اعداد","title_en":"Preparation"}]

اللغة

English

المصدر والدورية

اسم المصدر

Seismotectonics of Al-Refaei District and Surrounding Areas from Seismological and Geophysical Data Southern Iraq

المحتوى والصفحات

عدد الصفحات

0

إشراف وإعداد

الإشراف

Wathiq Ghazi Abdulnaby

الإعداد

Ali Ramthan Hussein

الاقتباسات الببليوغرافية