Erdek mareograf istasyonu ve çevresinde deniz seviyesi ve jeodezik ölçüler kullanılarak düşey yer kabuğu hareketlerinin araştırılması

Erdek mareograf istasyonu 17 Ağustos (Büyüklük($M_{w}$)=7.4) İzmit ve 12 Kasım ($M_{w}$=7.2) 1999 Düzce depremlerinin meydana geldiği Marmara bölgesinde bulunan tek mareograf istasyonudur. Erdek mareograf istasyonu son 17 yıllık aylık deniz seviyesi değerleri (1984-2001) düşey yer kabuğu hareketlerinin belirlenmesi amacıyla analiz edilmiştir. Harmonik analiz metodu ile en küçük karelerle dengelemede modele sadece istatistiksel olarak anlamlı gelgit bileşenleri ve doğrusal bir trend dahil edilerek 9.1 ± 1.0 mm/yıl büyüklüğünde önemli bir kara çökmesini işaret eden bağıl bir deniz seviyesi değişimi bulunmuştur. 1984-2001 dönemi ikiye bölünerek analiz yapıldığında, 1984-1989 dönemi için 10.8 ± 4.3 mm/yıl , 1990-2001 dönemi için ise 14.8 ± 1.9 mm/yıl büyüklüğünde relatif deniz seviyesi trend değeri bulunmuştur. 1992 yılından itibaren birisi Erdek mareograf istasyonu GPS noktası (ERDK), diğeri 3.7 km Erdek ilçesi yönünde bulunan GPS noktası (ERDE) olmak üzere iki farklı noktada yapılan tekrarlı GPS ölçüleri ve GPS noktaları ile mareograf röper noktası arasında yapılan periyodik duyarlı geometrik nivelman ölçülerinin birlikte analizi sonucunda, 16.1-16.7 mm/yıl düzeyinde deniz seviyesi trendi ile uyuşan bir kara çökmesi tespit edilmiştir.

Investigation of vertical crustal motion at Erdek tide gauge and surrounding region using sea level and geodetic data

Erdek tide gauge is the only tide gauge providing relatively longer records in the Marmara Sea region of Turkey where two devastating earthquakes occured in 1999, one in August 17 (Magnitude ($M_{w}$)=7.4) and the other in November 12 ($M_{w}$=7.2). Erdek tide gauge monthly sea level data covering the past 17 years (1984-2001) are analyzed to detect vertical crustal motion in the area. By using harmonic analysis method including only the statistically significant tidal constituents into the least squares fitting model, we found a relative sea level rate of 9.1 ± 1.0 mm/year with no significant acceleration, which points significantly the land subsidence in the area. By dividing the 1984-2001 period into two parts, a relative sea level rate of 10.8 + 4.3 mm/year for the period of 1984-1989 and of 14.8 ± 1.9 mm/year for the period of 1990-2001 are estimated. Analysis of periodic GPS measurements carried out at tide gauge GPS benchmark (ERDK) and at nearby GPS point (ERDE) 3.7 km away from the tide gauge towards Erdek town, and episodic levelling measurements made since 1994, result in land subsidence at the level of 16.1-16.7 mm/year which is in good agreement with sea level trend in the tide gauge area.

Kaynakça

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