ارزیابی خطر لرزه ای برای گسل شمال تبریز با تحلیل تمایل لغزش براساس تنش منطقه ای مستخرج از سازوکار ژرفی زمین لرزه ها و مشاهدات GPS

نوع مقاله : مقاله کامل پژوهشی

نویسندگان

دانشکده مهندسی عمران، دانشگاه تبریز

چکیده

تحلیل تمایل لغزش، ابزار با ارزشی جهت ارزیابی فعال شدن مجدد یک گسل و برآورد خطر لرزه­ای است. انجام این تحلیل ابزار مفیدی را جهت کمی ­سازی پتانسیل لغزش روی یک گسل فراهم می ­آورد. گسل و میدان تنش تحت بررسی می­تواند معلوم یا فرضی باشد. با استفاده از جهت لغزش احتمالی می­توان سازوکار ژرفی را نیز تعیین نمود که با استفاده از آن امکان بررسی سازگاری مابین سازوکارهای ژرفی با ساختارهای زمین ­شناسی وجود دارد. انجام این آنالیز هم در مورد یک گسل و هم در مجموعه­ ای از گسل­ ها امکان­پذیر است. پتانسیل لغزش به میدان تنش منطقه­ ای، جهت صفحه گسل و ضریب اصطکاک بستگی دارد. باتوجه به واقع‌شدن کلان­شهر تبریز در مجاورت گسل شمال تبریز، مطالعه پتانسیل لرزه­ای در این گسل از اهمیت ویژه­ای جهت تحلیل خطر لرزه­ای برای این شهر برخوردار است. در این تحقیق اطلاعات هندسی گسل از منابع مختلف استخراج و ثابت فرض شد. در ادامه تنش منطقه ­ای از منابع مختلف گردآوری شد. همچنین با استفاده از مشاهدات GPS تنش منطقه ­ای که بهترین انطباق را به منطقه موردمطالعه داشته باشد برآورد گردید. سپس تنش با استفاده از قانون کاوچی (Cauchy’s law) در راستای بخش­ های مختلف گسل و عمود بر آن­ها تجزیه و پتانسیل لغزش برای آن­ها با در نظرگرفتن درصد نسبت تنش برشی به نرمال محاسبه گردید. حالت­های مختلف تنش نتایج متفاوتی را برای تحلیل در پی داشتند. نکته قابل‌توجه در نتایج، تمایل لغزش بالای 50 درصد برای شاخه گسل گذرنده از شمال کلان­شهر تبریز می­باشد که پتانسیل رخداد زمین ­لرزه را در این بخش نشان می­دهد.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Seismic Hazard Assessment for the NTF by Slip Tendency Analysis based on the Regional Stress Extracted from the Focal Mechanism of Earthquakes and GPS Observables

نویسندگان [English]

  • Asghar Rastboud
  • Babak Shahandeh
  • Mehdi Mohamad-Zadeh
Faculty of Civil Engineering, University of Tabriz, Tabriz, Iran
چکیده [English]

The reactivation of slip on pre-existing planes of weakness is of key interest to many geological phenomena, being implicit for instance in tectonic inversion theory and in the concept of stick slip behavior. The analysis of reactivation is crucial in engineering geology where rock masses must be below the critical stress level needed to initiate sliding and in reservoir geology for selecting safe hydrocarbon traps. It also constitutes a valuable tool in seismic hazard assessment as it provides a means of quantifying the slip potential on mapped or suspected faults in a known or inferred stress field.

کلیدواژه‌ها [English]

  • Slip Tendency
  • Regional Stress Field
  • Focal Mechanism
  • GPS
  • North Tabriz Fault
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