GRAVİTE BELİRTİSİ AYRIMI TEKNİKLERİ ÜZERİNE KARŞILAŞTIRMALI BİR ÇALIŞMA

Year 2021, , 1276 - 1283, 20.12.2021

Yunus Levent Ekinci

https://doi.org/10.21923/jesd.938756

Abstract

Potansiyel alan yöntemlerinin doğasından dolayı elde edilen belirtiler sığ ve derin kökenli yapılardan kaynaklanan kısa ve uzun dalga boylu etkileri içerirler. Bu nedenle, gravite veya manyetik yöntemlerle gerçekleştirilen jeofiziksel aramada en önemli veri işlem adımlarından biri de belirti ayrımı işlemidir. Bu amaçla gözlemlenen veriyi rezidüel ve rejyonal belirti adı verilen iki bileşenine ayırmada bazı matematiksel teknikler kullanılmaktadır. Bu çalışmada, sonlu elemanlar yöntemi, tercihli filtreleme ve en uygun yukarı uzanım yüksekliği gibi üç hesaplama yönteminin etkinliği iyi bilinen ve günümüzde de en yaygın belirti ayrımı tekniği olarak kullanılan polinoma yaklaştırma yöntemiyle karşılaştırılmıştır. Uygulamada Jilin (Çin) manyetit alanı üzerinde alınmış gerçek gravite belirtisi kullanılmıştır. Elde edilen bulgular eleman şekil fonksiyonları kullanımıyla sonlu elemanlar yöntemi uygulamasının diğerlerine göre daha belirgin reziduel gravite belirtisi ürettiğini göstermiştir.

Keywords

Gravite Belirtisi Ayrımı, Sonlu Elemanlar, Filtreleme, Yukarı Uzanım, Polinoma Yaklaştırma

A COMPARISON STUDY ON THE GRAVITY ANOMALY SEPARATION TECHNIQUES

Abstract

Due to the nature of the potential field methods obtained anomalies include both short and long wavelength effects caused by shallow and deeper causative sources. Thus, anomaly separation procedure is one of the most important data processing steps in geophysical prospection performed via gravity or magnetic method. To that end, some mathematical procedures are performed to separate the observed data into two components, namely residual and regional anomalies. In this study, the efficiencies of three computational processes named finite element method, preferential filtering and optimal upward continuation height have been compared with the well-known polynomial fitting method which is still the most commonly used anomaly separation technique in potential field methods. In the applications a real gravity anomaly observed over the Jilin (China) magnetite area has been considered. Findings obtained have shown that performing finite element method with the use of element shape functions provides clearer residual gravity anomaly patterns than those of the others.

Keywords

Gravity Anomaly Separation, Finite Element, Filtering, Upward Continuation, Polynomial Fitting

References

• Blakely, R.J., 1995. Potential theory in gravity and magnetic applications. Cambridge: Cambridge University Press.
• Cheung, Y.K., Yeo, M.F., 1979. A practical introduction to finite element analysis. London: Pitman.
• Davis, J.C., 2002. Statistics and data analysis in geology. New York, NY, Wiley.
• Dobrin, M.B., 1976. Introduction to geophysical prospecting. New York, NY: McGraw Hill.
• Ekinci, Y.L., 2010. Gravity anomaly separation using finite element method. In 19th International Geophysical Congress and Exhibition. Ankara, Turkey. No. 59.
• Ekinci, Y.L., Yiğitbaş, E., 2012. Geophysical approach to the igneous rocks in the Biga Peninsula (NW Turkey) based on airborne magnetic anomalies: geological implications. Geodinamica Acta 25: 267-285.
• Ekinci Y.L., Yiğitbaş, E., 2015. Interpretation of gravity anomalies to delineate some structural features of Biga and Gelibolu peninsulas, and their surroundings (north-west Turkey). Geodinamica Acta 27: 300-319.
• Ekinci, Y.L., Balkaya, Ç., Göktürkler, G., Özyalın, Ş., 2021. Gravity data inversion for the basement relief delineation through global optimization: a case study from the Aegean Graben System, Western Anatolia, Turkey. Geophysical Journal International, 224, 923–944.
• Guo, L., Meng, X., Chen, Z., Li, S., Zheng, Y., 2013. Preferential filtering for gravity anomaly separation. Computers and Geosciences, 51, 247–254.
• Hedgley, D.R., 1978. An efficient algorithm for choosing the degree of a polynomial to approximate discrete nonoscillatory data. NASA Technical Memorandum, 72854.
• Kaftan, İ., Şalk, M., Sarı, C., 2005. Application of the finite element method to gravity data case study: Western Turkey. Journal of Geodynamics, 39, 431–443.
• Kaftan, İ., Şalk, M., Sarı, C., 2005. Performance of the finite element method for regional-residual separation on gravity method. Journal of the Balkan Geophysical Society, 13, 9–20.
• Lowrie, W., 2007. Fundamentals of geophysics. Cambridge: Cambridge University Press.
• Mallick, K., Sharma, K.K., 1997. Computation of regional gravity anomaly – A novel approach. Proceedings of the Indian Academy of Science (Earth and Planetery Sciences), 106, 55–59.
• Mallick, K., Sharma, K.K., 1999. A finite element method for computation of the regional gravity anomaly. Geophysics, 64, 461–469.
• Pawlowski, R.S., 1994. Green’s equivalent-layer concept in gravity bandpass filter design. Geophysics, 59, 69–76.
• Wang, J., Meng, X., Li, F., 2020. A computation scheme based on field attenuation rate for improving regional-residual separation of potential field data set. Journal of Geophysics and Engineering, 17, 117–126.
• Zeng, H., Xu, D., Tan, H., 2007. A model study for estimating optimum upward-continuation height for gravity separation with application to a Bouguer gravity anomaly over a mineral deposit, Jilin province, northeast China. Geophysics, 72, P145–P150.