مجله ژئوفیزیک ایران

مجله ژئوفیزیک ایران

شناسایی نشانه‌های ضعیف تهدیدات زمین‌لرزه با بررسی بزرگ‌نمایی امواج زلزله با طول‌موج بلند در منطقه مکران ایران

نوع مقاله : مقاله پژوهشی‌

نویسندگان
محمد عنایت کورچین قلعه 1
ابوذر سیفی کلستان 2
لیلا مجیدی 3
1 دکتری زلزله‌شناسی، دانشکده علوم زمین، دانشگاه تحصیلات تکمیلی در علوم پایه، زنجان، ایران
2 استادیار، پژوهشگر گروه عرصه‌های نوپدید، دانشگاه عالی دفاع ملی، تهران، ایران
3 دانشجوی دکترا، واحد علوم و تحقیقات، دانشگاه آزاد اسلامی، تهران، ایران
10.30499/ijg.2025.406200.1683
چکیده
در ادبیات آینده‌پژوهی مفهوم نشانه‌های ضعیف مفهومی پیشرو در سیستم‌ها و الگوهای پیش‌نگری محسوب می‌شود که به تدریج وارد حوزه‌های دیگر شده است. اصطلاح نشانه‌ ضعیف به اطلاعاتی گفته می‌شود که نادیده یا کم ارزش در  نظر گرفته شده‌اند و یا اطلاعات ناقصی در مورد آنها وجود دارد ولی بی‌تدبیری در مواجهه با آنها منجر به یک پیامد بزرگ می‌شود. مطالعه حاضر به بررسی اثر حوضه رسوبی بر تقویت دامنه امواج طول‌موج بلند زمین‌لرزه با دوره تناوب 1-10 ثانیه، در منطقه فرورانش مکران به عنوان یک تعریف فنی نشانه ضعیف در زلزله‌شناسی می‌پردازد. فرورانش مکران دارای حوضه‌ رسوبی با رسوبات ضخیم است که می‌تواند باعث تقویت دامنه امواج لرزه‌ای در طول‌موج‌های بلند (دوره تناوب بلند) شود. این پدیده به‌ویژه برای سازه‌های بلند در مناطق ساحلی اهمیت ویژه‌ای دارد. شکل و ساختار حوضه رسوبی از عوامل موثر در تقویت دامنه امواج زمین‌لرزه هستند و عواملی مانند تصحیحات ضریب گسترش هندسی و بزرگا، جذب ذاتی، سازوکار و موقعیت زمین‌لرزه‌ها، خطای مکان‌یابی، اختلاف مدل با زمین واقعی در محاسبه این تقویت دامنه خطا و عدم قطعیت وارد می‌کند. برای بررسی اثر حوضه رسوبی از شبیه‌سازی زمین‌لرزه‌ها و بررسی داده‌های زمین‌لرزه‌های محلی و دورلرز استفاده شده است. نتایج نشان می‌دهد که در منطقه مکران ساحلی، دامنه امواج لرزه‌ای در بازه دوره تناوب ۱ تا ۴ ثانیه تا حدود ۴ برابر تقویت می‌شوند. نتایج شبیه‌سازی در مقایسه با زلزله‌های محلی و دورلرز در قسمت‌هایی که مدل استفاده شده دقت بالایی دارد همخوانی خوبی دارد. تقویت دامنه امواج زمین لرزه در حالی اتفاق میافتد که نتایج اثر ساختار مرسوم (H/V) در دو ایستگاه واقع در مکران ساحلی، هیچ تشدید دامنه‌ای را نشان نمی‌دهد. این معیار به عنوان تعریف کارکردی از مفهوم نشانه ضعیف در مواجهه با خطر زمین‌لرزه ارائه می‌دهد که می‌تواند از غافل‌گیری سازمان‌ها در زمان بحران پیشگیری کند.
کلیدواژه‌ها
مکران ساحلی، تقویت دامنه امواج، تحلیل خطر زمین‌لرزه، نشانه‌‌های ضعیف، آینده‌پژوهی

موضوعات

عنوان مقاله English

Detection of weak signals of earthquake hazards by examining the amplification of long-wavelength seismic waves in the Makran region of Iran

نویسندگان English

Mohammad Enayat Kovarchin Ghaleh 1
Abouzar Seifi Kalestan 2
Leila Majidi 3
1 Ph.D. of Seismology, Department of Earth Sciences, Institute for Advanced Studies in Basic Sciences, Zanjan, Iran
2 Assistant Professor, Emerging Eras Research Group, SND University, Tehran, Iran
3 Ph.D. Student, Science And Research Branch, Islamic Azad University, Tehran, Iran
چکیده English

In the futures studies literature, weak signals are considered a pioneering and cutting-edge notion in forecasting systems and patterns. This concept has gradually entered other fields. The term weak signal refers to information that has been overlooked, undervalued, or is incomplete, yet mismanagement in addressing it can lead to significant consequences. This study explores how deep sedimentary basins in the Makran subduction zone amplify long-period seismic waves, creating potential risks for structures and infrastructures. The Makran region, spanning southeastern Iran and southwestern Pakistan, is known for its thick accretionary prism filled with soft sediments, which can significantly amplify seismic waves with long wavelengths (1-10s). This poses serious concerns for tall buildings, commercial ports, and industrial facilities. The geometry and structure of sedimentary basins are key factors influencing the amplification of earthquake ground motions. However, elements such as corrections for geometric spreading and magnitude, intrinsic attenuation, the mechanism and location of earthquakes, location errors, and discrepancies between models and actual ground conditions introduce errors and uncertainties in calculating this amplification. To better understand this effect, we performed 3D seismic wave simulations using the SPECFEM3D software, applying a recently developed shear wave velocity model for the region. We simulated 45 synthetic earthquakes with random locations and focal mechanisms to analyze spectral amplification on synthetic seismograms. In addition, we analyzed real seismic data from both local and teleseismic earthquakes recorded by local networks in the region. The findings revealed that coastal Makran of accretionary prism experiences significant wave amplification, with amplitudes increasing by 2.5 to 4 times for periods between 1 to 4 seconds. Interestingly, in eastern part of coastal Makran, data from real earthquakes showed slightly higher amplification compared to the simulations, likely due to differences between the velocity model and real earth, especially near the surface. This indicates that studying the site effect using the H/V method, especially for long wavelengths, is not always sufficient. Conventional methods may not accurately capture amplitude amplification of long-wavelength earthquake waves in the region. This can be considered as a weak signal in futures studies, and understanding it is crucial to preventing unexpected outcomes during crises. Earthquakes locating errors and considered approximations in correcting for geometric spreading and magnitude may also contribute to this discrepancy. Teleseismic earthquakes provided further evidence of strong amplification in the region, with some stations showing amplification up to five times compared to reference stations outside the basin. These findings underscore the critical need to account for the deep sedimentary basin effect in seismic hazard assessments for Makran, especially considering its growing urban and industrial development. The analysis reveals that long-period waves, which tend to resonate with tall buildings, pose the greatest risk. Ignoring these effects in seismic design could lead to underestimating ground motion intensity and increasing the risk of structural damage during major earthquakes. Ultimately, this study emphasizes the importance of improved seismic velocity models, expanded seismic monitoring networks, and more advanced 3D modeling to better predict seismic hazards and protect critical infrastructures in this economically important region.

کلیدواژه‌ها English

Coastal Makran, wave amplitude amplification, earthquake hazard analysis, weak signals, futures studies
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مجله ژئوفیزیک ایران
دوره 20، شماره 1
فروردین و اردیبهشت 1405
صفحه 53-74