مطالعۀ تغییرات آهنگ کرنش در منطقۀ گذار بین زاگرس و مکران با استفاده از داده های بردار سرعت GPS

نویسنده

استادیار گروه زلزله‌شناسی، پژوهشگاه بین‌المللی زلزله‌شناسی و مهندسی زلزله، تهران، ایران

چکیده

منطقۀ گذار بین زاگرس و مکران از جایگاه خاصی در مطالعات تکتونیکی منطقه برخوردار است. سازوکار گذار از ناحیۀ برخورد قاره ای در زاگرس به ناحیۀ فرورانش پوستۀ اقیانوسی به زیر پوستۀ قاره ای در مکران در این منطقه باعث به وجود آمدن سوالاتی از نقطه نظر زمین ساخت و ژئودینامیک شده است و این سوالات به نوبۀ خود انجام عملیات و مطالعات GPS در این منطقه و مناطق همجوار را باعث شده است. در این مطالعه از درون‌یابی بردارهای سرعت GPS بر روی یک شبکه مستطیل شکل و محاسبۀ کرنش در مرکز هر سلول برای مطالعۀ تغییرات آهنگ کرنش در این گستره استفاده شد. تغییرات مکانی قابل توجهی در محورهای اصلی آهنگ کرنش ژئودتیکی در قسمتهای مختلف منطقۀ گذار زاگرس و مکران مشاهده شد. بی‌هنجاری‌های مشاهده شده در کمیتهای محاسبه شده، با لرزه‌خیزی و سازوکار گسلش بر روی گسلهای مهم منطقه تطابق معنی داری را نشان داد. در این مطالعه همچنین برای نخستین بار روش جدیدی برای به نقشه درآوردن کمیتهای جهت دار به وسیلۀ مقیاسی رنگی با الگوی دایره ای پیشنهاد شد. راستای محورهای فشارشی آهنگ کرنش در منطقۀ مورد مطالعه به این روش به نقشه درآمد و بی‌هنجاری‌های قابل مشاهده در این نقشه با نقشه های آهنگ کرنش اتساعی و آهنگ کرنش برشی بیشینه مقایسه و مورد تعبیر و تفسیر بر مبنای واقعیات و مشاهدات زلزله شناختی قرار گرفت.

کلیدواژه‌ها


عنوان مقاله [English]

Seismic Hazard investigation by Strain Rate Variation Study in the Zagros-Makran Transition Zone by Using GPS Velocity Vector Data

نویسنده [English]

  • Sh. Pourbeyranvand
Assist. Prof., Dept., of Seismology, International Institute of Earthquake Engineering and Seismology, Tehran, Iran
چکیده [English]

The transition zone between the Zagros and Makran has a special place in tectonic studies in the region. The mechanism of the transition from the continental collision in the Zagros to the oceanic-continental subduction in Makran has raised some questions from the tectonics and geodynamics point of view, and these questions, in turn, has caused GPS campaigns and studies in this region and adjacent areas. In this study, the interpolation of GPS velocity vectors on a rectangular grid and strain calculation in the center of each cell was used to study the strain rate variations in this range. Noticeable spatial changes in the principal axes of the geodetic strain rate were observed in different parts of the Zagros and Makran transition zones. The anomalies observed in the calculated quantities showed significant correlations with seismicity and mechanisms of faulting on important faults in the region. In this study, a new method for mapping directional quantities utilizing a color scale with a circular pattern is also proposed for the first time. The direction of the strain rate axes in the study area was mapped by this new method and the anomalies observed were compared with the areal and maximum shear strain rate maps and interpreted based on seismological facts and observations.

کلیدواژه‌ها [English]

  • areal
  • GPS
  • Maximum shear
  • strain rate
  • Zagros Makran transition zone
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