تحلیل خطر احتمالاتی سونامی در امتداد ساحل جنوب‌شرق ایران

نوع مقاله: مقاله تحقیقی‌ (پژوهشی‌)

نویسندگان

1 گروه فیزیک زمین، موسسه ژئوفیزیک دانشگاه تهران، تهران ایران

2 پژوهشکده علوم زمین، پژوهشگاه صنعت نفت، تهران، ایران

چکیده

علی‌رغم ابهام در رفتار لرزه‌زایی زون فرورانش مکران در ساحل جنوب‌شرق ایران که به‌دلیل لرزه‌خیزی کم آن است، شواهد تاریخی و سونامی سال 1945 میلادی، بیان‌کننده پتانسیل سونامی‌زایی این زون هستند. رخداد سونامی‌های محتمل در آینده، ایران را بیش از هر کشور دیگری در معرض خطر ناشی از آن قرار خواهد داد. تحلیل خطر احتمالاتی سونامی، راهی مؤثر برای ارزیابی خطر ناشی از سونامی‌ها و کمکی جهت برنامه‌ریزی برای آینده است. در این مطالعه، با درنظرگرفتن زون فرورانش مکران، مکران غربی و مکران شرقی به‌عنوان چشمه‌های تولیدکننده سونامی، به برآورد خطر احتمالی سونامی در ساحل جنوب‌شرق ایران پرداخته شد. سناریوهایی برای وقوع زمین‌لرزه‌هایی با بزرگای بین 5/7 تا 9/8 برای مکران‌ غربی و مکران شرقی و سناریوهایی با بزرگای بین 5/7 تا 1/9 برای کل مکران درنظرگرفته‌شد. در این تحقیق، از نتایج مدل‌سازی عددی سونامی برای تحلیل خطر احتمالاتی سونامی استفاده شد. نتایج، ساحل کنارک (واقع در استان سیستان و بلوچستان، جنوب‌شرق ایران) را خطرپذیرترین ناحیه ساحلی در میان نقاط مهم مختلف برای سناریوهای مورد مطالعه نشان داد. کمترین خطرپذیری نیز از آن سیریک (واقع در استان هرمزگان، جنوب ایران) است. نتایج، حاکی از لزوم توجه به خطر درازمدت سونامی در این منطقه مهم از کشور ایران، به‌خصوص ناحیه بین جاسک و بریس است.

کلیدواژه‌ها


عنوان مقاله [English]

Probabilistic tsunami hazard assessment along the southeastern Iran coast

نویسندگان [English]

  • Amin Rashidi 1
  • Nasser Keshavarz Farajkhah 2
1 Institute of Geophysics, University of Tehran, Tehran, Iran
2 Geoscience Division, Research Institute of Petroleum Industry (RIPI), Tehran, Iran
چکیده [English]

Despite the ambiguous tsunamigenic behavior of the Makran Subduction Zone (MSZ), due to the low level of offshore seismicity, historical evidences and the 1945 tsunami in Makran confirm the potential of the MSZ for generating tsunami events. Possible future tsunamis generated by the MSZ will pose the coastlines of Iran to hazard more than any other country. Probabilistic tsunami hazard assessment (PTHA) is an effective approach to assess hazard from tsunamis and help for planning for the future. In this study, we assess the probabilistic tsunami hazard along the southeastern coast of Iran considering the entire Makran, the western Makran and the eastern Makran tsunamigenic sources.
Tsunami scenarios include earthquakes of magnitudes between 7.5-8.9 for the western and eastern Makran and between 7.5-9.1 for the entire Makran. Both seismicity and tsunami numerical simulation are inputs for probabilistic hazard analysis. Assuming that the tsunami sources are capable of generating tsunamigenic earthquakes, estimating the annual rate of these events is required for PTHA. The truncated Gutenberg-Richter relation (Cosentino et al., 1977 and Weichert, 1980) is used in this study to compute the annual number of the earthquakes. We model tsunamis using the COMCOT well-known algorithm (Liu et al., 1998). The distributions of tsunami heights along the coastline of Iran are used in probabilistic tsunami hazard assessment.
The results of PTHA show that Konarak and Sirik coastlines are posed to the most and least hazard from tsunamis, respectively. The probability of exceeding (POE) 1 and 3 meters increases with time. The probability that tsunami wave height exceeds 3 meters in 500 years is about 0.63 and 0 near the coastlines of Konarak and Sirik, respectively. The maximum POE for 3 meters belongs to the area between Beris and the west of Kereti. Distributions of probabilistic tsunami height along the coastline of Iran also indicate that Konarak and Sirik are the most and least vulnerable shorelines to tsunami hazard, respectively. The annual probability of exceeding 1, 2 and 3 meters are 1, 0.4 and 0.2, respectively. The results indicate the need of attention to tsunami long-term hazard along the southeastern coast of Iran, especially for the area between Jask and Beris.
Our tsunami hazard assessment does not involve the tsunami inundation distances on dry land due to lack of high resolution site-specific bathymetric/topographic maps. Such computations are required in order to estimate the exact impacts of possible future tsunamis on the southeastern coast of Iran. High-resolution hydrographic surveys are required to be done in future for the major ports. Furthermore, future works should consider other possible near-field tsunami sources, such as the Murray Ridge, Minab-Zendan and Sonne faults and far-field tsunami sources, such as the Sumatra-Andaman subduction zone.

کلیدواژه‌ها [English]

  • Makran
  • Tsunami
  • southeastern Iran
  • probabilistic hazard assessment
  • Numerical modeling
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