بررسی اثر ناهمگنی چینه‌ای بر توزیع تنش حاصل از فعالیت گسل‌های راندگی پنهان با استفاده از مدل‌سازی عددی

نوع مقاله : مقاله پژوهشی

نویسندگان

1 گروه زمین شناسی، دانشکده علوم، دانشگاه گلستان، گرگان، ایران

2 عضو هیات علمی/ گروه زمین شناسی، دانشکده علوم، دانشگاه گلستان

3 گروه عمران، دانشکده فنی و مهندسی، دانشگاه گلستان، گرگان، ایران

4 دانشیار بخش زمین‌شناسی دانشکده علوم و معاون مرکز پژوهشی زلزله دانشگاه شهید باهنر کرمان

چکیده

گسل‌های راندگی پنهان در سطح زمین قابل مشاهده نیستند اما در طی حوادث لرزه ای قادر به رشد و انتقال تنش به سمت سطح و نواحی پیرامون می‌باشند. توالی پوشاننده گسل‌های پنهان ممکن است از واحدهای رسوبی مختلفی تشکیل شده باشند که می‌تواند در نحوه رشد گسیختگی و توزیع تنش ناشی از جنبش این گسل‌ها تاثیرگذار باشد. در این پژوهش، چگونگی اثر ناهمگنی چینه‌ای بر توزیع تنش، با استفاده از روش عددی (روش اجزای محدود) مورد ارزیابی قرار گرفته است. نتایج شبیه‏ سازی نشان می دهد که تمرکز تنش در لایه نمک و توالی رویی آن نسبت به مدل همگن کاهش محسوسی پیدا کرده است. در حالی که در لایه‌های زیرین نمک نسبت به وضعیت همگن، افزایش تنش بیشتر در محدوده‌ بزرگتری اتفاق افتاده است. علاوه براین، مقایسه نمودارهای توزیع جابجایی قائم در دو مدل همگن و ناهمگن نشان می‌دهند که با وجود الگوی توزیع مشابه، میزان جابجایی در مدل ناهمگن بیشتر از مدل همگن می‌باشد. بنابراین، می‌توان اظهار داشت که حضور لایه‌های شکل‌پذیر مشابه نمک، از یک سو موجب افزایش احتمال رشد گسیختگی (به دلیل تمرکز تنش) در لایه‌های زیرین و کاهش یا توقف رشد گسیختگی به سمت لایه های رویی و سطح زمین (به سبب کاهش شدید تنش در لایه شکل‌پذیر) شود. از طرف دیگر، به دلیل بالاتر بودن میزان دگرشکلی (جابجایی) در لایه های رویی تشکیل ساختارهای جدید چین و گسل را تسهیل می‌کنند.

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