مجله ژئوفیزیک ایران

مجله ژئوفیزیک ایران

بازنگری لرزه‌زمین‌ساخت شمال‌غرب ایران و شرق ترکیه

نوع مقاله : مقاله پژوهشی‌

نویسندگان
1 دانشجوی دکتری ژئوفیزیک، دانشکده علوم زمین، دانشگاه تحصیلات تکمیلی علوم پایه زنجان، زنجان، ایران
2 استاد، دانشکده علوم زمین، دانشگاه تحصیلات تکمیلی علوم پایه زنجان، زنجان، ایران
3 دانشیار، دانشکده علوم زمین، دانشگاه تحصیلات تکمیلی علوم پایه زنجان، زنجان، ایران
4 دانشیار، دانشگاه فلوریدای جنوبی
چکیده
به منظور بررسی لرزه‌زمین‌ساخت شمال‌غرب ایران و شرق ترکیه با استفاده از روش مکان‌یابی چند رویدادی تجزیه هایپوسنتروئید، تعداد 12 خوشه لرزه‌ای شامل 2149 زمین‌لرزه مکان‌یابی مجدد، تعداد 688 زمین‌لرزه با خطای بین 2 تا 3 کیلومتر تعیین عمق و تعداد 234 سازوکار کانونی برای این رخدادها محاسبه شد. در این کار، همه داده‌های موجود برای بررسی همبستگی گسله‌های فعال شناخته شده با لرزه‌خیزی و سازوکارهای آن‌ها، یافتن گسله‌های جدید احتمالی و برآورد سازوکار گسله‌های فعال در منطقه استفاده شده تا مدل کینماتیکی تغییرشکل در منطقه بهبود داده شود. نتایج نشان می‌دهد مرزهای اصلی تکتونیکی تعریف شده در شمال­غرب ایران و شرق ترکیه و سازوکارهای آنها تا حد زیادی معتبر است. اغلب لرزه­خیزی در مرز بلوک­ها متمرکز شده اما در بخشی از بلوک‌های وان و شمال‌غرب ایران لرزه­خیزی درون بلوک نیز کشیده شده است. بیشترین لرزه­خیزی بر روی گسله شمال تبریز و ادامه آن به سمت سامانه‌های گسلی گلاتو-سیاه­چشمه-خوی و چالدران متمرکز شده بطوریکه فعالیت لرزه‌ای، بیشتر بخش­های این گسله‌ها را در طول زمان ثبت دستگاهی فراگرفته است. نتایج ما روند لرزه­خیزی متمرکزی از زاگرس به سوی سلماس با سازوکار کششی را نشان می­دهد. افزون بر این، روند لرزه‌خیزی دیگری با سازوکار راستالغز راست‌بر نیز دیده می­شود که از پایانه سامانه گسلی اصلی جوان زاگرس شروع شده و به جنوب شرق آناتولی ختم می­شود. الگوی لرزه‌خیزی در خوی، هندسه و سازوکار گسلی پیچیده‌تر از نقشه‌های ساده گسلی موجود را پیشنهاد می‌کند. همچنین سازوکار راستالغز راست‌بر در مرز تالش و خزرجنوبی جهت تایید مدل‌های تکتونیکی قبلی مشاهده نشد و نتایج مکان­یابی مجدد، لرزه‌خیزی بر روی گسله جنوب بسکله و گسله مراغه را نشان نمی‌دهد. یک روند شما‌ل‌غربی-‌جنوب‌شرقی از زلزله‌های نیمه عمیق راستالغز با جزء نرمال، زیرراندگی صفحه حوضه خزر جنوبی به زیر کورا را پیشنهاد می‌کند.
کلیدواژه‌ها

موضوعات


عنوان مقاله English

Reapprisal of seismotectonics of northwest Iran and east Turkey

نویسندگان English

Salman Andayeshgar 1
Abdolreza Ghods 2
,Esmaeil Shabanian 3
Jochen Braunmiller 4
1 Ph.D. Student, Department of Earth Sciences, Institute for Advanced Studies in Basic Sciences, Zanjan, Iran
2 Professor, Department of Earth Sciences, Institute for Advanced Studies in Basic Sciences, Zanjan, Iran
3 Associate Professor, Department of Earth Sciences, Institute for Advanced Studies in Basic Sciences, Zanjan, Iran
4 Associate Professor, University of South Florida
چکیده English

To investigate the seismotectonics of NW Iran and East Turkey using the multi-event hypocentroid decomposition method, 12 seismic clusters comprising 2,149 relocated earthquakes were analyzed. Among these, 688 earthquakes were assigned focal depths with uncertainties of 2–3 km, and 234 focal mechanisms were calculated for these events. In this study, all available datasets were utilized to examine correlations between known active faults and their associated seismicity and mechanisms, identify potential new faults, estimate the mechanisms of active faults in the region and finally revise the kinematic deformation model of the region. The results confirm that the primary tectonic boundaries defined in NW Iran and East Turkey, along with their associated mechanisms, remain largely valid, with most seismicity concentrated along block boundaries. However, intra-block seismicity is observed within parts of the NW Iran and Van blocks. The seismicity pattern indicates that the majority of the seismic activity is concentrated along the right-lateral strike-slip North Tabriz Fault and its continuation toward the Gailatu-SiahCheshmeh-Khoy and Chalderan fault systems. Instrumental records reveal that seismic activity has persistently affected most segments of these faults over time. Our findings highlight a prominent and concentrated seismicity trend with normal mechanisms extending from the Zagros Mountains toward Salmas. Additionally, another seismicity trend with right-lateral strike-slip mechanisms is observed, initiating at the terminus of the Zagros Main Recent Fault System and extending toward southeast Anatolia. Furthermore, two newly identified trends perpendicular to the North Tabriz Fault, with a northeast orientation, emerge in the data. These may indicate the presence of fault segments characterized by left-lateral strike-slip mechanisms, which partially accommodate the displacement along the North Tabriz Fault. The distribution of aftershock cloud and variety of their focal mechanisms indicate that the fault geometry and mechanism in Khoy are more complex than the existing simplified fault maps suggest. Notably, the right-lateral strike-slip mechanisms along the Talesh–South Caspian boundary as proposed in earlier tectonic models were not observed. Similarly, the relocated seismicity does not show any seismic activity along the south Baskale fault or the Maragheh fault. Based on earthquake focal depths and focal mechanisms, we hypothesize that faults parallel to the western Caspian fault are responsible for deep strike-slip earthquakes with a transtensional component in the Kura Basin. The intermediate-depth events may suggest underplating of northwestern region of SCB beneath Kura basin. The focal and centeriod depths indicate that the depth of the earthquakes along the primary boundaries of tectonic blocks ranges from 10 to 12 kilometers. However, within the blocks, specifically in the Ahar-Varzeqan cluster, as well as in the Zagros region, including the Oshnaviyeh and Bashkal clusters the depth of earthquakes is larger. This may be due to the young and immature nature of the faults responsible for these earthquakes. Additionally, the depth of earthquakes in the Talesh region and the South Caspian Basin may exceed 40 kilometers, indicating seismic activity occurring within the cold igneous crust of the South Caspian Basin lying beneath a thick sedimentary cover.

کلیدواژه‌ها English

Seismicity, relocation, tectonics, NW Iran, east Turkey
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دوره 20، شماره 1
فروردین و اردیبهشت 1405
صفحه 111-146

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