استفاده از نرم‌افزار ComMIT در پهنه‌بندي خطر سونامي در سواحل جاسك

Application of ComMIT Software in Tsunami Hazard Zoning in the coast of Jask

درياي عمان به واسطه وجود منطقه‌ي فرو‌رانش در نزديكي ساحل ايران در صورت وقوع زلزله‌اي با بزرگي بالا در بستر دريا، سونامي، خسارات شديدي به تأسيسات ساحلي و مسكوني وارد خواهد آورد. در سونامي ششم دي ماه 1383، با وجودي كه بين كانون زمين‌لرزه اقيانوس هند و شهرهاي ساحلي ايران در كنار درياي عمان فاصله‌ي زيادي وجود داشت، موج‌هاي سونامي در شهر چابهار خسارت‌هاي اندكي بر جاي گذاشت. اين به آن معنا است كه اگر كانون ‌زمين‌لرزه به ساحل ايران نزديك‌تر باشد، شهرهاي ساحلي ايران نيز با خطر جدي روبه‌رو مي‌شوند. با توجه به اين‌كه ايران در كمربند زلزله‌خيز جهان قرار دارد، وقوع سونامي در درياي عمان امري دور از ذهن نخواهد بود. از اين رو، ضرورت مطالعه‌ي جامع درباره‌ي سونامي در درياي عمان احساس مي‌شود. در اين مقاله سعي شده است كه علاوه بر مطالعه‌ي زمين‌شناسي مكران به بررسي تاريخچه‌ي وقوع سونامي در سواحل درياي عمان پرداخته شد. علاوه بر اين، با استفاده از داده‌هاي حاصل شده درGIS و مدل‌سازي در نرم‌افزار ComMIT وقوع سونامي در سواحل درياي عمان مدل‌سازي و بر روي تصاوير ماهواره‌اي نشان داده شد. شهر جاسك به دليل موقعيت راهبردي خود در درياي عمان و تمركز تأسيسات نظامي و بندري و برنامه‌ريزي‌هاي بلند‌مدتي كه براي توسعه‌ي اين بندر در دست اجرا است اهميت بسيار فراواني در درياي عمان دارد. از اين رو، مدل‌سازي وقوع سونامي با دقت بسيار در اين منطقه اجرا شد. نتايج به دست آمده نشان مي‌دهد كه ميزان تأثير‌پذيري اين منطقه از سونامي، با توجه به بزرگي زلزله به وقوع پيوسته و موقعيت جغرافيايي سواحل اين شهر، گوناگون است و در شديدترين زلزله بخش مهمي از تأسيسات ساحلي آسيب جدي خواهد ديد.

In the Tsunami of Dec. 26, 2004, although there was a large distance between the earthquake center of Indian Ocean and coastal cities of Iran, the Tsunami waves brought some damages in Chabahar coast. This means that if the earthquake center was closer to Iran, Iran’s coastal regions would have confronted serious danger... In the present study, we used ComMIT software (Community Model Interface for Tsunami) as a research tool, Inundation modeling was done for the Jask coastal area in order to assess the potential and find out the impact of tsunami from any future Makran Subduction Zone earthquake. Computer modellings programs help analyze sea-level data to generate forecasts of tsunami wave height and the expected inundation for specific coastal areas. In this research we use ComMIT software. For modeling the wave, the assumption for 10*100 Km blocks is applied. In this formulation, the approximate for wave behavior is represented for coastal regions. In this modeling, three steps of gridding with different preciseness are used. By assuming an earthquake by magnitude of 8.6 Richter and movement of 6 blocks mentioned in the subduction area close to Jask, each block rises about 16 m. the first impact by coast by a wave of 2 m height knocks up the coast at 26 minutes. according to the performed modeling, the first change after Tsunami is reduction in sea level and this procedure continues till 11 minutes after that. In this time, the maximum amount of water regress from coastal line for 2 m is observed. After this time, the first wave attacks Jask. The first wave impacts Jask headland and then affects the whole eastern coast of Jask. The wave height in this region in 26 minutes after Tsunami reaches to 2 m and starts approaching in the coast. This process occurs in the western coast of Jask by a 10-minute delay. The first tall wave impacts western coast at 36 minutes after Tsunami and regresses for about 2.5 Meter. The second wave is ready to attack the western coast and 40 minutes after Tsunami the second wave attacks eastern coast. The height of this wave in its maximum is about 2.5 Meter. According to investigation of existing models concerning influence of Jask city by Tsunami is divided to three sections: A) eastern coast of Jask, B) Jask headland, C: western coast. The eastern coast us the first region that is confronting attack of the greatest waves and the maximum rate of wave march in the coast (about 1 Km) is in this region. In this area the slope is about 1% and concerning topography, it provides an appropriate condition for wave on the coast. In eastern coast of Jask, there is an intense concentration of governmental offices and military centers including Jask airport and Admiral Force’s quay. In the first waves caused by Tsunami, these installations would be damaged severely and in second and third waves this process continues.