بررسی روش‌های مختلف برآورد کرنش و تنش لرزه‌ای و برآورد نرخ کوتاه‌شدگی پوسته زمین در ایران با به‌کارگیری سازوکار زمین‌لرزه‌‌ها

نوع مقاله: مقاله پژوهشی

نویسنده

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

چکیده

در این پژوهش، تنش، کرنش و نرخ کوتاه‌شدگی پوسته زمین در ایران با روش‌های کاسترف و مولنار برآورد شده و هم‌چنین نقش منطقه‌بندی در برآوردها نیز بررسی شده است. در این راستا، شمار 637 زمین‌لرزه با بزرگای گشتاوری بزرگ‌تر از 5/5 در بازه زمانی سال‌های 1909 تا 2016 به‌کار برده شده است. راستای فشار، کشش و کرنش لرزه‌ای با دو روش (بلوک‌بندی و هر زمین‌لرزه جداگانه) و هم‌چنین کوتاه‌شدگی افقی و تغییرات قائم پوسته زمین برآورد شده‌اند. راستای فشار و کشش و اندازه کرنش لرزه‌ای به‌دست آمده از سازوکار زمین‌لرزه‌ها به سه ‌صورت برآورد شد: هر زمین‌لرزه جداگانه، منطقه‌بندی º1׺1 و منطقه‌بندی زمین‌ساختی. داده‌پردازی نشان می‌دهد که راستای فشار و کشش و اندازه کرنش لرزه‌ای شدیدا به نوع منطقه‌بندی وابسته است. هم‌چنین، برآورد اندازه کرنش لرزه‌ای با دو روش کاستروف و مولنار با یکدیگر تفاوت آشکاری نشان می‌دهند. با این حال می‌توان گفت، بیش‌ترین دگرشکلی در ایران در گستره دشت‌بیاض و قائن در خاور ایران روی می‌دهد. برآورد سرعت قائم پوسته زمین در زاگرس فراخاسته، ستبرشدگی و در فروافتادگی پیش‌بوم زاگرس، نازک‌شدگی پوسته را به‌دنبال داشته، که هم‌خوانی خوبی با زمین‌ساخت گستره دارد. اگرچه، در البرز خاوری این برآورد فراخاست بوده، در البرز باختری فرونشست به‌دست آمده که با زمین‌ساخت البرز که یک گستره برخوردی فشاری و مایل است هم‌خوانی ندارد.

کلیدواژه‌ها


عنوان مقاله [English]

Investigation of various stress and strain determination methods and crustal shortening in Iran using focal mechanism of the earthquakes

نویسنده [English]

  • Majid Nemati
Department of Geology, University of Kerman, Kerman, Iram
چکیده [English]

In this research, stress, strain and crustal shortening were calculated in Iran using Kastrov and Molnar methods and also role of gridding in the estimations has been investigated. In this view, numbers of 637 earthquakes with moment magnitude greater than 5.5 in time interval of 1909-2016 were applied. Pressure and tension directions, seismic strain resulted by two methods (gridding and every earthquake individually) and also horizontal and vertical crustal displacement velocity were estimated. Pressure and tension directions and seismic strain deduced by earthquake focal mechanisms, were calculated in three manners: every earthquake individually, 1°×1° and tectonical grindings. Data processing shows that pressure and tension directions and seismic strain are intensely related to the kind of the gridding. Also, there is clear difference between estimation of the strain with the two methods of Kastrov and Molnar. Nevertheless, it could be concluded that maximum deformation is going on in Dasht-e Bayaz and Qaen area in the eastern Iran. Vertical velocity estimations in High Zagros and Zagros Foredeep are crustal thickening and thinning, respectively, which is in accordance well to tectonic of the area. Although, this estimation in eastern and western Alborz are uplift and subsidence, respectively, which the later one is not in accordance with Alborz tectonic with an oblique collision.

کلیدواژه‌ها [English]

  • Strain
  • Stress
  • Earth crust
  • Earthquake
  • Mechanism
  • Iran
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