Jose a. Alvarez GOMEZ, Emilio CARRENO, Jose M. Martinez SOLARES, Mauricio GONZALEZ, Maitane OLABARRIETA, Luis OTERO

The impact of tsunamis on the island of Majorca induced by north Algerian seismic sources

Kuzey Cezayir Balearic adalarını tehdit eden deprem kaynaklı tsunami dalgalarının kaynaklandığı ana bölgeyi oluşturmaktadır. Bu çalışmada olası en kötü deprem yırtığını tesbit etmek amacına yönelik olarak 1980 El Asnam ve 2003 Boumerdes-Zemmouri depremleri gibi önemli deprem serileri incelendi. Yaklaşık 13 km derinlikte bulunan fay düzlemine kadar ulaşan deprem yırtığının boyutları 55 km × 16 km olarak tahmin edildi. Doğrultu lokal tektonik yapıya uyarlanırken, eğim ve yan yatma açıları sabitler olarak kabul edildi ve değerleri sırasıyla 50° ve 90° olarak değerlendirildi. Bu karakteristik özellikler dikkate alınarak 4 metrelik ortalama bir kayma miktarı için deprem büyüklüğü $M _w$= 7.3 olarak hesaplandı; bu değerler bölgenin sismotektonik özellikleriyle uyumludur. Ceyazir’in kuzey kıyılarında dokuz farklı kaynak önerilmiştir; kaynakların bazıları kıyıdan uzak açık denizde haritalanırken, daha az bilinen diğer kaynaklar olasılıkla kıyıya yakın yapıların devamı niteliğindedir. Sayısal simülasyon çalışmaları ile potansiyel dokuz depremin yaratacağı olası tsunami dalgalarının Majorca adası üzerindeki etkileri çalışıldı. Bu kaynaklardan Balearic Adalarında felaket getirecek tsunami dalgalarının tetiklenemeceği görüldü. Ancak, tarihi depremlerde olduğu gibi dalga yükselikleri 2 metreyi bulacak tsunamiler alçak alanlarda, dalga büyümesi ise koy ve limanlarda sele neden olabilir.

Kuzey Cezayir sismik kaynaklarından uyarılmış tsunami dalgalarının Majorca adasındaki etkileri

The north of Algeria is the main earthquake-related tsunami generation zone that threatens the Balearic Islands. In this work we review the major seismic series of the area –the 1980 El Asnam and the 2003 Boumerdes- Zemmouri earthquakes– in order to obtain a probable worst characteristic earthquake rupture. We estimate rupture dimensions of 55 km × 16 km, reaching the fault plane a depth of 13 km. The dip and rake have been taken as constants, with values of 50° and 90° respectively, while the strike is adjusted to the local tectonic structure. With these characteristics a magnitude $M _w$= 7.3 earthquake is obtained for an average slip of 4 metres; these values being reasonable for the seismotectonics of the area. Nine sources along the northern coast of Algeria have been proposed, some of them have been mapped offshore and others that are less known are probable continuations of onshore structures. Based on numerical simulations the tsunami impacts of the nine potential events on Majorca have been studied. Catastrophic tsunamis cannot be triggered from these sources in the Balearic Islands. However, wave elevations up to 2 m can generate flooding in low areas and wave amplifications in bays and harbours that can be damaging, as witnessed in historical events.

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