Interpretation of Gravity and Magnetic Anomalies Using Linear Transformations and Derivative Based Techniques: Biga Peninsula Example

Abstract

The most important points in the interpretation of gravity and magnetic anomalies are the data quality and the selection of the data processing techniques. In the potential field methods, which involve many analysing techniques, in order to process and analyse the data there is a necessity of selecting the techniques which can be suitable to the nature of the problem. From the beginning of 21th century, computer systems and the programming languages, which are developed based on the technological developments, have been effectively used in every engineering branches. Many numerical processes can be easily performed in MATLAB programming environment. Thus, we have performed some algorithms coded by us to gravity and magnetic anomalies in order to interpret the subsurface structure of tectonically active Biga Peninsula which hosts every kind of geologic rock groups. Firstly regional effects were computed using finite element method and then they removed from the gravity and magnetic data. Before performing horizontal derivatives, analytic signal and boundary analysis techniques to the data sets, some linear transformations such as reduction to the pole and preudogravity were applied to magnetic data. The resulting maps showed that high amplitude magnetic anomalies are located on the plutonic rocks such as Ezine-Kestanbol, Ilıca-Şamlı and Kuşçayırı. Residual gravity anomaly map indicated the high amplitude gravity responses between the zones of Biga-Çan-Yenice, Manyas-Balya-İvrindi and Bayramiç-Ayvacık-Ezine and on the vicinity of Bandırma and Balıkesir. Low amplitude anomalies were detected in the western part of the Biga Peninsula that lie towards the Aegean cost. The derivative-based maps also showed a nearly-circular anomaly pattern at the western part of the Peninsula, in which the county of Bayramiç is the centre. It was seen that this centre is characterized by high amplitude anomalies. Additionally, in order to determine the density and magnetization intensity variation in depth, three-dimensional normalized full gradient technique was applied to the data sets for every 200 m depth levels. It is thought that performing these kinds of techniques to the geologically-known other regions would yield remarkable knowledge in terms of the spatial extent of the geological structures with depth.

Full text

66. Türkiye Jeoloji Kurultayı 1-5 Nisan/April 2013 66th Geological Congress of Turkey
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81
INTERPRETATION OF GRAVITY AND MAGNETIC ANOMALIES
USING LINEAR TRANSFORMATIONS AND DERIVATIVE BASED
TECHNIQUES: BIGA PENINSULA EXAMPLE
Yunus Levent Ekinci a, Erdinç Yiğitbaş b
a Çanakkale Onsekiz Mart University, Faculty of Engineering and Architecture, Department of
Geophysical Engineering, 17020, Çanakkale
b Çanakkale Onsekiz Mart University, Faculty of Engineering and Architecture, Department of
Geological Engineering, 17020, Çanakkale
( ylekinci@comu.edu.tr )
ABSTRACT
The most important points in the interpretation of gravity and magnetic anomalies are the data
quality and the selection of the data processing techniques. In the potential field methods,
which involve many analysing techniques, in order to process and analyse the data there is a
necessity of selecting the techniques which can be suitable to the nature of the problem. From
the beginning of 21th century, computer systems and the programming languages, which are
developed based on the technological developments, have been effectively used in every
engineering branches. Many numerical processes can be easily performed in MATLAB
programming environment. Thus, we have performed some algorithms coded by us to gravity
and magnetic anomalies in order to interpret the subsurface structure of tectonically active
Biga Peninsula which hosts every kind of geologic rock groups. Firstly regional effects were
computed using finite element method and then they removed from the gravity and magnetic
data. Before performing horizontal derivatives, analytic signal and boundary analysis
techniques to the data sets, some linear transformations such as reduction to the pole and
preudogravity were applied to magnetic data. The resulting maps showed that high amplitude
magnetic anomalies are located on the plutonic rocks such as Ezine-Kestanbol, Ilıca-Şamlı and
Kuşçayırı. Residual gravity anomaly map indicated the high amplitude gravity responses
between the zones of Biga-Çan-Yenice, Manyas-Balya-İvrindi and Bayramiç-Ayvacık-Ezine and
on the vicinity of Bandırma and Balıkesir. Low amplitude anomalies were detected in the
western part of the Biga Peninsula that lie towards the Aegean cost. The derivative-based maps
also showed a nearly-circular anomaly pattern at the western part of the Peninsula, in which
the county of Bayramiç is the centre. It was seen that this centre is characterized by high
amplitude anomalies. Additionally, in order to determine the density and magnetization
intensity variation in depth, three-dimensional normalized full gradient technique was applied
to the data sets for every 200 m depth levels. It is thought that performing these kinds of
techniques to the geologically-known other regions would yield remarkable knowledge in terms
of the spatial extent of the geological structures with depth.
Key words: Algorithms, Biga Peninsula, gravity, magnetic, subsurface structures.