ارزیابی مشخصات سونامی زمین لغزشی احتمالی در دریاچه خزر

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشکده فنی، گروه مهندسی عمران، دانشگاه گیلان، رشت، ایران

2 دانشکده فنی، گروه مهندسی عمران، دانشگاه شیراز، شیراز، ایران

چکیده

سونامی‌ها محدود به اقیانوس‌های آزاد نیستند؛ در خلیج‌ها، فلات‌ها، دریاهای درون مرزی و دریاچه‌ها نیز باید انتظار وقوع سونامی را داشت. دریای خزر نیز به عنوان بزرگترین دریاچه‌ی جهان با خطوط ساحلی طولانی و تراکم جمعیتی زیادی که در اطراف خود دارد و با توجه به سونامی‌های خفیفی که در گذشته در آن رخ داده، باید بیشتر مورد بررسی قرار گیرد تا از حوادث مخرب آینده جلوگیری شود. در تحقیق حاضر با استفاده از مدل‌سازی عددی و نیمه تحلیلی و فرض وجود زمین لغزش در قسمت‌های میانی و جنوبی دریای خزر، پارامترهای مهم سونامی‌های حاصل بدست آمده و سری زمانی ارتفاع موج که مهم‌ترین خروجی تحلیل و مدل‌سازی سونامی می‌باشد، در ده ایستگاه که از جمله بنادر مهم دریای خزر هستند ارائه شده است. نتایج نشان می‌دهد که ارتفاع موج اولیه‌ی سونامی‌ها قابل توجه بوده و به دلیل ماهیت انتشار شعاعی امواج سونامی زمین لغزشی، مناطق نزدیک تحت تأثیر قرار خواهند گرفت. هر چقدر عمق محل زمین لغزش کمتر باشد، ارتفاع موج اولیه بیشتر و طول موج کمتر می‌شود، یعنی موج پر انرژی‌تر خواهد بود و توانایی گسترش به نقاط بیشتری را خواهد داشت. در واقع وقتی زمین لغزش از عمق کمتری شروع به حرکت می‌کند، مسافت بیشتری را تا رسیدن به کف حوضه طی می‌کند و در نتیجه حجم آب جابه جا شده بیشتر و دامنه ی موج بلندتر خواهد بود. با توجه به نتایج حاصل از مدل سازی، احتمال وقوع سونامی در دریاچه خزر ناشی از زمین لغزش وجود داشته و در صورت وقوع، سونامی مهیبی مشاهده خواهد شد.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Tsunami Generation and its Characteristics Due to Land Slide in the Caspian Sea

نویسندگان [English]

  • Fariba Ghanbarpour 1
  • Seyyed Ahmad Neshaei 1
  • Mehdi Veiskarami 2
1 Civil Engineering Department, University of Guilan, Rasht, Iran
2 School of Engineering, Shiraz University, shiraz
چکیده [English]

Tsunami waves can be generated in any coastal area, including inland seas and large lakes. Although there exists enough information about the generation and propagation of tsunami in the ocean environment, the assessment of such phenomenon in lakes with finite depth still suffers from the lack of theoretical work and sufficient measured data. The Caspian Sea is the largest lake in the world and has gone through different historical tsunami events. A numerical study for prediction of tsunami wave height time series for ten locations in the Caspian Sea is presented in this work. Unlike tsunamis generated by earthquakes, submarine landslide tsunamis generated in shallow waters were more destructive compared to those generated in deep water. This is due to the higher energy that can be converted from the slide to the water in shallow areas. Moreover, shallower waters were usually closer to the coasts and thus a shorter available distance exists for radial damping. The dispersion of short waves and also radial spreading decrease the far-field effects of landslide tsunamis in contrast to tsunamis of seismic origins. However, shorter waves were more prone to coastal amplification with higher local effects. The results of predictions were consistent with the previous finding reported in the literature indicating the possibility of tsunami occurrence in large lakes due to landslide which can affect the neighboring ports and area located particularly in the central and southern areas of the Caspian Sea.

کلیدواژه‌ها [English]

  • Caspian Sea
  • Landslide
  • Numerical modeling
  • risk assessment
  • Tsunami
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