DOI: https://doi.org/10.24028/gzh.0203-3100.v42i2.2020.201746

Gravity anomalies of the Southeast Caucasus

G.R. Sadygova

Abstract


The article studies gravity anomalies of disturbing masses by the values of the power spectrum and digital filtering of gravity data. The calculation of the power spectrum and digital filtering is performed using the Hartley transform and Butterworth filter. Processing of gravimetric data in the frequency component makes it possible to estimate the depths of anomaly-forming sources by analysing the radial spectrum. The logarithm of the power spectrum is graphically described depending on the spatial frequency, to determine the depth of density boundaries. The low-frequency and high-frequency components and the cutoff frequency are determined from the curve of the logarithm of the power spectrum. The cutoff frequency separating the regional and local components is determined by the point of intersection of the lines obtained by approximating the data of the power spectrum in the long and short wavelength components. The cutoff frequency (wavenumber) is determined to be equal to ωc = 0.16 rad/km in this case. Low-frequency and high-frequency components are accepted as components of regional and local anomalies. The power spectrum indicates depths of 16.6 km for the long component and 1.8 km for the short components. The depth of 16.6 km is connected with the surface of the crystalline basement, and 1.8 km with the surface inside the Cenozoic sediments. Good agreement between the results of filtering gravimetric data of the Southeast Caucasus using the Hartley transform and the one-dimensional Butterworth filter with the results of previous studies confirm the reliability of the results.The interpretation of the regional anomalies shows that these anomalies depend on geometry crystalline basement.


Keywords


power spectrum; hartley transform; gravity anomaly; Southeast Caucasus

References


Amiraslanov, T.S. (1978). Methodology and results of anisotropic transformations of the gravitational field of the Caspian-Guba oil-and-gas region. Izvestiya VUZov. Neft i gaz, (10), 8―11 (in Russian).

Akhundov, A.B., Veremeenko, O.B., & Shekinskiy, E.M. (1996). Regional studies. In: Geophysical exploration in Azerbaijan. Baku: Sharg-Garb, 282 p. (in Russian).

Bat, M. (1980). Spectral analysis in geophysics. Moscow: Nedra, 535 p. (in Russian).

Gadzhiev, P.M. (1965). The deep geological structure of Azerbaijan. Baku: Azerneshr, 200 p. (in Russian).

Alizade, A. (Ed.). (2005). Geology of Azerbaijan. Vol. V. Physics of the Earth. Baku: Nafta-Press, 352 p. (in Russian).

Alizade, A. (Ed.). (2008). Geological map of Azerbaijan. Scale 1 : 500 000. Explanatory letter. Baku: Nafta-Press, 86 p. (in Russian).

Kirillova, I.V., Lustikh, E.H., Rastvorova, B.A., Sorskiy, A.A. & Khain, B.E. (1960). Analysis of geotectonic development and seismicity of the Caucasus. Moscow: Publ. House of the Academy of Sciences of the USSR, 340 p. (in Russian).

Kadirov, F.A. (2000). Gravitational field and models of the deep structure of Azerbaijan. Baku: Edition of the Institute of Geology of the Azerbaijan Academy of Sciences, 112 p. (in Russian).

Kolesova, V.I. (1985). Analytical methods of magnetic cartography. Moscow: Nauka, 222 p. (in Russian).

Nikitin, A.A. (1986). The theoretical basis of the processing of geophysical information. Moscow: Nedra, 342 p. (in Russian).

Serkerov, C.A. (1991). Spectral analysis in gravity and magnetic exploration. Moscow: Nedra, 279 p. (in Russian).

Sneddon, I. (1955). Fourier Transform. Moscow: Publ. House of Foreign Literature, 668 p. (in Russian).

Strakhov, V.N. (1997). About a new stage in the development of the theory of interpretation of gravitational and magnetic fields. Izvestiya AN SSSR. Ser. Fizika Zemli, (12), 20―41. (in Russian).

Tsimelzon, I.O. (1965). The deep structure of the earth's crust and tectonics of Azerbaijan according to geophysical research. Sovetskaya geologiya, (4), 103―111 (in Russian).

Tsimelzon, I.O., & Amiraslanov, T.S. (1980). Integration of detailed gravity and seismic surveys in the junction zone of the Absheron, Shemakhino-Kobystan and Caspian-Cuban oil and gas regions of Azerbaijan. Neftegazovaya geologiya i geofizika, (8), 44―47 (in Russian).

Bhattacharyya, B.K. (1966). Continuous spectrum of the total magnetic anomaly due to a rectangular prismatic body. Geophysics, 31(1), 97―121. https://doi.org/10.1190/1.1439767.

Blakely, R.J. (1995). Potential theory in gravity and magnetic applications. Cambridge University Press. 441 p.

Bracewell, R.N. (1986). The Fourier Transform and Its Applications. New York: McGraw-Hill Book Co. 474 p.

Duka, B. (1998). Comparison of different methods of analysis of satellite geomagnetic anomalies over Italy. Annals of Geophysics, 41(1), 49―61. https://doi.org/10.4401/ag-3793

Haines, G. (1990). Spherical cap harmonic analysis. Journal of Geophysical Research: Solid Earth, 90(B3), 2583―2592. https://doi.org/10.1029/JB090iB03p02583.

Hartley, R.V.L. (1942). A more symmetrical Fourier analysis applied to transmission problems. Proc. of the IRE, 30(2), 144―150.

Kadirov, F.A. (2000). Application of the Hartley transform for interpretation of gravity anomalies in the Shamakhy-Gobustan and Absheron oil and gas-bearing regions, Azerbaijan. Journal of Applied Geophysics, 45(1), 49―61. https://doi.org/10.1016/S0926-9851(00)00018-5.

Kadirov, F.A. (2000). Filtering of Gravity Date Using the Hartley Transform: A Case Study of the Kura Intermontane Trough. Izvestiya. Physics of the Solid Earth, 36(10), 866―871.

Kulhanek, O. (1976). Introduction to digital filtering in geophysics. Amsterdam—Oxford—New York: Elsevier Scientific Publishing Company. 168 p.

Mohan, N.L. & Anand, B.L. (1994). A note on 2D Hartley Transform. Geophysics, 59(7), 1150―1155. https://doi.org/10.1190/1.1443670.

Rao, B.N., Rama, K.P. & Markandeyulu, A. (1995). Mapros ― A computer program for basement mapping and filtering of gravity and magnetic data using a Hartley transform. Computer & Geosiences, 22(3), 197―218. https://doi.org/10.1016/0098-3004(95)00073-9.

Saatcilar, R. Ergintav, S. & Canitez, N. (1990). The use of the Hartley transform in geophysical applications. Geophysics, 55(11), 1488―1495. https://doi.org/10.1190/1.1442796.

Spector, A., & Grant, F.S. (1970). Statistical models for interpreting aeromagnetic data. Geophysics, 35(2), 293―302. https://doi.org/10.1190/1.1440092.

Sundararajan, N. (1995). 2D Hartley transforms. Geophysics, 60(1), 262―267 https://doi.org/10.1190/1.1443754.


Refbacks

  • There are currently no refbacks.


Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.

Creative Commons License
Geofizicheskiy Zhurnal is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

Flag Counter