A Comparative Study on Computing Horizontal Derivatives of Gravity Data for Geological Contact Mapping

Yıl 2017, , 209 - 222, 01.04.2017

Yunus Levent Ekinci

https://doi.org/10.25288/tjb.303025

Cited By: 1

Öz

Computations of x- and y-components of the horizontal derivatives (gradients) from an anomaly grid (with x- and y-axes directed east and north, respectively) still take an important place in potential field data-processing techniques. These techniques may successfully bring out some significant subtle details that are masked in the anomaly maps. Particularly abrupt lateral changes in densities and magnetizations effectively aid geological mapping and these changes may be traced by some derivative-based techniques without specifying any prior information about the nature of the potential field source bodies. Hence derivative-based techniques are regularly used in the visual interpretation of potential field anomalies. It is well known that computation of horizontal derivatives can be performed through either fast Fourier transform (i.e. in wave number domain) or simple finite-difference equations (i.e. in space domain) to outline the geological source boundaries (edges). Numerous studies including the use of either one have been recorded in the literature so far. In this study, comprehensive comparisons of the solutions obtained from those techniques have been made using both synthetically produced and real gravity data sets. Synthetic applications have been performed using both noise-free and noisy gravity data sets for two different depth-to-source scenarios. Thus not only the signal-to-noise ratios but also the depth-to-source conditions have been analyzed to test the performance of those approaches. Additionally, a real data experiment has been achieved using regional Bouguer gravity anomalies from a portion of a well-known geological setting, the Aegean Graben System (Western Anatolia, Turkey).

Anahtar Kelimeler

Fast Fourier transform, Finite-differences, First-order horizontal derivatives, Geological contact mapping, Gravity anomalies

Kaynakça

• Blakely, R.J., 1995. Potential Theory in Gravity and Magnetic Applications. Cambridge: Cambridge University Press.
• Blakely, R.J. and Simpson, R.W., 1986. Approximating edge of source bodies from magnetic or gravity anomalies. Geophysics, 51, 1494–1498.
• Boschetti, F., 2005. Improved edge detection and noise removal in gravity maps via the use of gravity gradients. Journal of Applied Geophysics, 57, 213–25.
• Bozkurt, E., 2003. Origin of NE-trending basins in western Turkey. Geodinamica Acta, 16, 61–81.
• Cooper, G.R.J., 2002. An improved algorithm for Euler deconvolution of potential field data. Leading Edge, 21, 1197–1198.
• Cooper, G.R.J. and Cowan, D.R., 2006. Enhancing potential field data using filters based on the local phase. Computers & Geosciences, 32, 1585–1591.
• Cooper, G.R.J. and Cowan, D.R., 2008. Edge enhancement of potential-field data using normalized statistics. Geophysics, 73, H1–H4.
• Cooper, G.R.J. and Cowan, D.R., 2009. Terracing potential field data. Geophysical Prospecting, 57, 1067–1071.
• Cooper, G.R.J. and Cowan, D.R., 2011. A generalized derivative operator for potential field data. Geophysical Prospecting, 59, 188–194.
• Cordell, L. and Grauch, V.J.S., 1982. Reconciliation of the discrete and integral Fourier transform. Geophysics, 47, 237–243.
• Cordell, L. and Grauch, V.J.S., 1985. Mapping basement magnetization zones from aeromagnetic data in the San Juan Basin, New Mexico, In: W.J., Hinze, (ed.), The utility of regional gravity and magnetic anomaly maps: Society Exploration Geophysics, Tulsa, Oklahoma, 181–197.
• Çiftçi, N.B. and Bozkurt, E., 2009. Evolution of the Miocene sedimentary fill of the Gediz Graben, SW Turkey. Sedimentary Geology, 216, 49–79.
• Ekinci, Y.L., 2010. A Matlab-based interactive data processing and interpretation software package for gravity and magnetic anomalies: GMINTERP, 19th International Geophysical Congress and Exhibition, Ankara, Turkey, 60.
• Ekinci, Y.L. and Yiğitbaş, E., 2012. A 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., Ertekin, C. and Yiğitbaş, E., 2013. On the effectiveness of directional derivative based filters on gravity anomalies for source edge approximation: Synthetic simulations and a case study from the Aegean graben system (western Anatolia, Turkey). Journal of Geophysics and Engineering, 10, 035005.
• Ekinci, Y.L., Balkaya, Ç., Şeren, A., Kaya, M.A. and Lightfoot, C.S., 2014. Geomagnetic and geoelectrical prospection for buried archaeological remains on the Upper City of Amorium, a Byzantine city in Midwestern Anatolia, Turkey.
• Ekinci, Y.L. and 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 (4), 300–319.
• Fedi, M. and Florio, G., 2001. Detection of potential fields source boundaries by enhanced horizontal derivative method. Geophysical Prospecting, 49, 40–58.
• Helvacı, C., 2015. Geological features of Neogene basins hosting borate deposits: an overview of deposits and future forecast, Turkey. Bulletin of the Mineral Research and Exploration, 151, 169–215.
• Li, Z.G. and Ma, Z.H., 2014. A new approach for filtering and derivative estimation of noisy signals. Circuits, Systems, and Signal Processing, 33, 589–598.
• Li, L., Huang, D., Han, L. and Ma, G., 2014. Optimised edge detection filters in the interpretation of potential field data. Exploration Geophysics, 45, 171–176.
• Menke, W., 1984. Geophysical Data Analysis: Discrete Inverse Theory: Academic Press Inc, New York.
• Miller, H.G and Singh, V., 1994. Potential field tilt-a new concept for location of potential field sources. Journal of Applied Geophysics, 32, 213–217.
• MTA (General Directorate of Mineral Research and Exploration of Turkey), 2002. Geological map of Turkey, MTA Publications scale: 1/500000, Ankara, Turkey.
• MTA (General Directorate of Mineral Research and Exploration of Turkey), 2006. Bouguer gravity anomaly map of Turkey, MTA Publications scale: 1/2000000, Ankara, Turkey.
• Plouff, D., 1976. Gravity and magnetic fields of polygonal prisms and application to magnetic terrain correction. Geophysics, 41, 727–741.
• Purvis, M. and Robertson, A., 2005. Miocene sedimentary evolution of the NE–SW-trending Selendi and Gördeş Basins, W Turkey: implications for extensional processes. Sedimentary Geology, 174, 31–62.
• Roest, W.R., Verhoef, J. and Pilkington, M., 1992. Magnetic interpretation using the 3-D analytic signal. Geophysics, 57, 116–125.
• Roy, I.G., 2013. On computing gradients of potential field data in the space domain. Journal of Geophysics and Engineering, 10, 035007.
• Salem, A., Williams, S., Fairhead, D., Smith, R. and Ravat, D., 2008. Interpretation of magnetic data using tilt-angle derivatives. Geophysics, 73, L1–L10.
• Sarı, C. and Şalk, M., 2002. Analysis of gravity anomalies with hyperbolic density contrast: an application to the gravity data of western Anatolia. Journal of Balkan Geophysical Society, 5, 87–96.
• Sarı, C. and Şalk, M., 2006. Sediment thickness of the western Anatolia graben structures determined by 2D and 3D analysis using gravity data. Journal of Asian Earth Sciences, 26, 39–48.
• Seyitoğlu, G., 1997. Late Cenozoic tectono-sedimentary development of the Selendi and Uşak-Güre basins: a contribution to the discussion on the development of east–west and north trending basins in western Turkey. Geological Magazine, 134, 163–175.
• Sözbilir, H., Sarı, B., Uzel, B., Sümer, Ö. and Akkiraz, S., 2011. Tectonic implications of transtensional supradetachment basin development in an extension-parallel transfer zone: the Kocaçay Basin, western Anatolia, Turkey. Basin Research, 23, 423–448.
• Verduzco, B., Fairhead, J.D., Green, C.M. and MacKenzie, C., 2004. The meter reader–New insights into magnetic derivatives for structural mapping. The Leading Edge, 23, 116–119.
• Wanyin, W., Yu, P. and Zhiyun, Q., 2009. A new edge recognition technology based on the normalized vertical derivative of the total horizontal derivative for potential field data. Applied Geophysics, 6, 226–33.
• Wang, Z., Krebes, E.S. and Ravat, D., 2008. High precision potential field and gradient-component transformations and derivative computations using cubic B-splines. Geophysics, 73, I35–I42.
• Wang, J., Meng, X.H. and Li, F., 2015. Improved curvature gravity gradient tensor with principal component analysis and its application in edge detection of gravity data. Journal of Applied Geophysics, 118, 106–114.
• Wijns, C., Perez, C. and Kowalczyk, P., 2005. Theta map: Edge detection in magnetic data. Geophysics, 70, L39–L43.
• Yuan, Y., Gao, J. and Chen L., 2016. Advantages of horizontal directional Theta method to detect the edges of full tensor gravity gradient data. Journal of Applied Geophysics, 130, 53–61.
• Zhang, H.L., Tian-You, L. and Yu-Shan, Y., 2011. Calculation of gravity and magnetic source boundaries based on anisotropy normalized variance. Chinese Journal of Geophysics 54, 560–567.
• Zuo, B. and Hu, X., 2015. Edge detection of gravity field using eigenvalue analysis of gravity gradient tensor. Journal of Applied Geophysics, 114, 263–270.