تجزیه و تحلیل فرکتالی پس‌لرزه‌های زمین‌لرزه 1392 گشت-سراوان، شمال شرق مکران
محورهای موضوعی :عبدالرضا پرتابیان 1 , شجاع انصاری 2 , فریده جهاندیده 3
1 - دانشگاه سیستان و بلوچستان
2 - اداره کل زمین‌شناسی و اکتشافات معدنی گیلان
3 - دانشگاه سیستان و بلوچستان
کلید واژه: مکران# پهنه فرورانش# پس‌لرزه# لرزه‌خیزی# بعد فرکتال#,
چکیده مقاله :
در این پژوهش بعد فرکتالی پس‌لرزه‌های زمین‌لرزه سال 1392 گشت – سراوان و ارتباط آن با پارامترهای لرزه‌خیزی (b-value) همچنین نسبت انرژی منتشر شده توسط زمین‌لرزه اصلی و پس‌لرزه‌ها مورد بررسی قرار گرفته است. زمین‌لرزه اصلی، یک زمین‌لرزه درون ورقه فرورونده با سازوکار نرمال بوده و ناشی از فعالیت گسل سراوان نمی‌باشد. بررسی بعد فرکتالی پس‌لرزه‌ها و ارتباط آن با b-value وجود یک منبع لرزه‌ای خطی نظیر پهنه فرورانش را تایید می‌نماید. از طریق بعد فرکتال می‌توان نسبت لغزش در گسل‌های اصلی و ثانویه را نیز برآورد نمود. این نسبت نشان می‌دهد که بخش کمی از لغزش‌ها از طریق گسل‌های نزدیک به سطح زمین صورت گرفته است که این موضوع از طریق عمق پس‌لرزه‌های رخ داده در نزدیکی این گسل‌ها قابل تایید می‌باشد. بنابراین وقوع زمین‌لرزه اصلی در عمق زیاد موجب آزاد شدن انرژی و انتقال آن به اعماق کم و فعال نمودن گسل‌ها و شکستگی‌ها شده است که رخداد پس‌لرزه‌ها هم در اعماق نزدیک به زمین‌لرزه اصلی و هم در اعماق کم و نزدیک به سطح زمین می‌تواند تایید کننده آن باشد. نسبت کل انرژی منتشر شده در طی توالی پس‌لرزه‌های زمین‌لرزه گشت-سراون به انرژی منتشر شده توسط زمین‌لرزه اصلی نشان می دهد که قسمت اعظم انرژی منتشر شده مربوط به زمین‌لرزه اصلی بوده و تنها درصد کمی مربوط به پس‌لرزه‌ها می‌باشد.
In this paper the fractal dimension of the aftershocks of the 2013 M 7.8 Gosht-Saravan earthquake and their relationship with the seismicity parameters (such as the b-value) and also the released seismic energies of the main shocks and the aftershocks are investigated. The Gosht-Saravan main shock is an intraslab event with normal mechanism. No relationship between the Saravan fault and the main shock is observed. By examining the fractal dimension of the aftershocks and their relationship with the b-value it is confirmed that a linear seismic source (such as a subduction zone) exists. The slip ratio between the primary and secondary faults can be estimated by the fractal dimension. The calculated slip ratio indicates that a low portion of the slips may be related to the near surface fractures which can be verified by the shallow depth aftershocks. The earthquake occurrence in the intermediate depth, releases seismic energy and migrates to the near surface faults and fractures. The occurrence of aftershocks both near the hypocenter and at shallow depths can confirm the activity of these faults. The ratio of the total radiated seimic energy of the aftershocks to the radiated seimic energy of the main shock indicates that a high fraction of the energy related to the main shock and just a small fraction of the energy related to the aftershocks.
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