Bürhan KOZLU, Mustafa YILMAZ

Güncel Yüksek Dereceli Küresel Model Temelli Gravite Anomalilerinin Karşılaştırılması

Yeryüzü sistemi, yer yüzeyinde gözlemlenebilen farklı doğal olgular oluşturur: Kütle deformasyonları ve levha tektoniklerine, depremlere ve volkanizmaya yol açan yer değiştirmeler gibi. Dünya'nın iç yapısı, fiziksel yüzeyi ve atmosferi ile ilişkili dinamik süreçler, jeodezinin üç ana yapısını etkiler: Dünyanın şekli, yer çekimi alanı ve dönüşü. Jeodezi, tüm yeryüzü sisteminin tanımlanması, izlenmesi ve kestirimi için karakteristik bir yapı oluşturur. Jeodezide geleneksel ve yeni araçlar, gözlenen büyüklükler ve teknikler yer çekimi alanı ile ilgilidir. Bu nedenle jeodezi, yeryüzünün fiziksel yüzeyi üzerinde yapılan jeodezik gözlemleri, konumların matematiksel olarak tanımlandığı geometrik bir yüzeye dönüştürmek için yerçekimi alanını ve onun zamansal değişimini izler. Bu çalışmada, yerçekimi alan modellemesinin ana bileşenleri, (Serbest-hava ve Bouguer) gravite anomalileri, seçilen bir çalışma alanı üzerinde güncel yüksek dereceli küresel modellerle (EIGEN6C4, GECO ve WGM2012) hesaplanmıştır. Model temelli gravite anomalileri, Türkiye'de bulunan bölgesel ölçekteki çalışma alanı için en uygun küresel modeli belirlemek amacıyla, standart sapma (SS) ve karesel ortalama hata (KOH) bakımından, karasal gravite verisi ile karşılaştırılmıştır. Serbest-hava gravite anomali farkları için en küçük SS (13.45 mGal) ve KOH (15.42 mGal) WGM2012 tarafından elde edilmiştir. Bouguer gravite anomali farkları için, EIGEN6C4 en küçük SS (8.05 mGal) ve KOH (8.12 mGal) değerini sağlamıştır. Sonuçlar, EIGEN6C4'ün, çalışma alanı üzerinde yeryüzünün yer çekimi alanını modellemek için yararlı bir araç olabileceğini göstermiştir.

The Comparison of Gravity Anomalies based on Recent High-Degree Global Models

The Earth system generates different phenomena that are observable at the surface of the Earth suchas: Mass deformations and displacements leading to plate tectonics, earthquakes, and volcanism. Thedynamic processes associated with the interior, surface, and atmosphere of the Earth affect the threepillars of geodesy: Shape of the Earth, its gravity field, and its rotation. Geodesy establishes acharacteristic structure in order to define, monitor, and predict of the whole Earth system. Thetraditional and new instruments, observable, and techniques in geodesy are related to the gravity field.Therefore, the geodesy monitors the gravity field and its temporal variability in order to transform thegeodetic observations made on the physical surface of the Earth into the geometrical surface in whichpositions are mathematically defined. In this paper, the main components of the gravity field modelling,(Free-air and Bouguer) gravity anomalies are calculated via recent high-degree global models(EIGEN6C4, GECO, and WGM2012) over a selected study area. The model-based gravity anomalies arecompared with the corresponding terrestrial gravity data in terms of standard deviation (SD) and rootmean square error (RMSE) for determining the best fit global model in the study area at a regional scalein Turkey. The least SD (13.45 mGal) and RMSE (15.42 mGal) were obtained by WGM2012 for theFree-air gravity anomaly residuals. For the Bouguer gravity anomaly residuals, EIGEN6C4 provides theleast SD (8.05 mGal) and RMSE (8.12 mGal). The results indicated that EIGEN6C4 can be a useful tool formodelling the gravity field of the Earth over the study area.

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