Kocaeli 1999 depreminin kıyı alanları üzerindeki etkileri ve İstanbul kıyıları

Abstract

ÖZET Depremlerin ülke ekonomimiz üzerine getirdiği yük oldukça fazladır. 17 Ağustos 1999 depremi Yalova-Kocaeli-Sakarya-Bolu illerinde en fazla olmak üzere İstanbul, Eskişehir, Bursa, Zonguldak gibi çevre illerde de çok sayıda can kaybı ve hasara yol açmıştır. Bu depremin zararı toplam 18373 hayat, 285,000 ev ve 42,000 iş yeridir. Deprem 15 milyar dolar mertebesinde ekonomik zarar meydana getirmiştir. Deniz yansımalı sismik verilerine göre 17 Ağustos kırığı deniz altmda Başiskele'den itibaren batıya doğru 50 km daha gitmektedir. Kocaeü 1999 depreminde çalışan ana fay sağ yanal doğrultu atımlı bir faydır ve Körfez içinde D-B yönünde gevşeyen büklümler yaparak uzanmaktadır. Körfez içinde ana faya bağlı olarak çalışmış normal faylar da vardır. Kıyı bölgelerindeki esas hasar doğrultu bileşenli ana faya bağlıdır. Normal fayların ise depremle birlikte gelişen depreşim dalgalarının oluşumumda etkisi olabilir. Elverişsiz zemin koşulları, özellikle alüviyonla kaplı bölgelerde ve kıyı alanlarında hasarın büyük olmasına neden olmuştur. Deprem ayrıca sıvılaşma ve kıyı heyelanlarına da neden olmuştur. Sıvılaşma özellikle Adapazarı ve Düzce ovalarında gözlenirken, Sapanca Gölü güneyinde kum kaynamaları gözlenmiştir. Bu nedenle birçok bina

ABSTRACT On August 17, 1999 a catastrophic earthquake of 7.4 magnitude with an epicenter near Gölcük hit the Marmara region causing 18.373 causalities, more than 25.000 injuries and extensive damage. Nearly 285.000 houses collapsed or heavy damaged due to faulting, resulting ground ruptures and the effect of poor ground conditions. This movement and accompanying liquefaction, ground settlement and lateral ground flows in soft soils also resulted in extensive and permanent flooding of large areas along the south coasts of Izmit Gulf and Sapanca Lake. Property damage is estimated to be over $15 billion. The quake disrupted transportation, utilities and communication systems in the region. On the basis of seismic reflection data, the surface rupture is estimated to have propagated 50 km further west in the Izmit Bay. The main fault activated in the earthquake is west trending right lateral strike slip along the Izmit Bay with some releasing bends. There are also some small scale normal faults associated with the main fault. The main damage along the coastal areas are due to the dextral strike-slip main fault, whereas normal faults may cause tsunamigenic events associated with the earthquake. Secondary effects of the quake included liquefaction and landslides. Ground failures caused by soil liquefaction formed in extensive areas mainly in the Adapazari- Düzce plain. Sand boils were observed along the south cost of the Sapanca Lake. Some buildings was catastrophically damaged due to soil liquefaction. On the one hand, the coastal area located on delta deposits and artificial material along the seashore slided into the bay. Subsidence and coastal landslides have left substantial portions of the towns Gölcük, Hahdere, Ulaşlı, and Değirmendere inundated with sea water. The impact of earthquakes in coastal areas prone to disastrous earthquakes necessitate the analysis of associated risk for rational formulation of mitigation strategies. The seismic risk can be best quantified through the preparation of `Earthquake Damage and Loss Scenarios`. The act of totally ignoring geological and geotechnical properties of an area being considered for coastal development, industrial facilities, and then building cities and holiday villages on alluvial ground that has no resistance against an earthquake considerably; constructing buildings and bridges on the active faults; and erecting, industrial facilities in landslide zones-these represent the most typical examples of ignorance and lack of awareness of the reality that it is located in earthquake zones. vu