GEOPHYSICAL RESEARCH, 2016, vol.17, no.3, pp. 70-87. DOI: 10.21455/gr2016.3-6
UDC 534.2, 622.02
Abstract References Full text (in Russian) Full text (in English)
ON THE ORIGIN OF SEISMIC ANISOTROPY IN ROCKS: EXPERIMENTAL AND THEORETICAL STUDIES ON BIOTITE GNEISS SAMPLES
I.Yu. Zel(1,2), T.I. Ivankina(1), T. Lokajicek(3), H. Kern(4), D.M. Levin(2)
(1) Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Dubna, Russia
(2) Tula State University, Tula, Russia
(3) Institute of Geology Academy of Sciences Czech Republic, Prague, Czech Republic
(4) Institute of Earth Sciences, University of Kiel, Germany
Abstract. The paper presents the results of experimental and theoretical investigations on highly anisotropic layered plagioclase-biotite gneiss and biotite gneiss of weak anisotropy. We used two different methods for measuring seismic anisotropy: measurements of P-wave ray velocities on a sphere and comprehensive measurements of P- and S-wave phase velocities on a cube under different confining pressures. The combination of P-wave velocity spatial distribution with S-wave velocities in three orthogonal directions was used to recover the elastic moduli of anisotropic rock samples. The crystallographic preferred orientations (CPOs) of major minerals were measured by time-of-flight neutron diffraction. On the basis of CPO the effective media modeling of elastic properties was performed using different inclusion methods and averaging procedures. In our work for the first time we implemented a nonlinear approximation of the P-wave velocity-pressure relation for estimation of mineral matrix properties and orientation distribution of microcracks. From the theoretical modeling we found that the bulk elastic anisotropy of the sample is controlled by the CPOs of micas grains and microcracks. The comparison of theoretical calculations of elastic properties with ultrasonic measurements showed large discrepancies in S-wave velocities.
Keywords: biotite gneiss, elastic wave velocities, crystallographic texture, compositional layering, seismic anisotropy.
References
Aleksandrov K.S. and Prodajvoda G.T., Anizotropiya uprugih svojstv mineralov i gornyh porod (Anisotropy of elastic properties of minerals and rocks), Novosibirsk: Publishing House SB RAS, 2000.
Bayuk I.O. and Ryzhkov V.I., Opredelenie parametrov treshchin i por karbonatnyh kollektorov po dannym volnovogo akusticheskogo karotazha. Tekhnologii sejsmorazvedki, 2010, no. 3, pp. 32–42.
Zel I.Yu., Ivankina T.I., Levin D.M., and Lokajicek T., Application of a modified method of ultrasonic measurements for determination of elastic moduli of rocks. Crystallography Reports, 2015, vol. 60, no. 4, pp. 537–545.
Zel I.Yu., Ivankina T.I., Levin D.M., and Lokajicek T., P-wave ray velocities and the inverse acoustic problem for anisotropic media. Crystallography Reports, 2016, vol. 61, no. 4, pp. 623-629.
Ivankina T. I. and Matthies S., On the development of the quantitative texture analysis and its application in solving problems of the Earth sciences. Physics of Particles and Nuclei, 2015, vol. 46, no. 3, pp. 366–423.
Shermergor T. D., Teoriya uprugosti mikroneodnorodnyh sred (The theory of elasticity of microinhomogeneous media), Nauka: Moscow, 1977.
Babuska V. and Cara M, Seismic Anisotropy in the Earth, Kluwer Academic Publishers, Dordrecht. 1991.
Backus G.E., Long-wave elastic anisotropy reduced by horizontal layering, J. Geophys. Res., 1962, vol. 67, pp.4427–4440.
Bass J.D., Elasticity of minerals, glasses, and melts, in Mineral Physics and Crystallography: A Handbook of Physical Constants. AGU Ref. Shelf, vol. 2. Edited by T. J. Ahrens. AGU. Washington D. C. 1995.
Birch F., The velocity of compressional wave velocities in rocks to 10 kbar, J. Geophys. Res., 1961, vol. 66, pp.2199–2224.
Crampin S., A review of wave motion in anisotropic and cracked elastic-media, Wave motion, 1981, vol. 3, pp.341–391.
Keppler R., Ullemeyer K., Behrmann J.H., and Stipp M., Potential of full pattern fit methods for the texture analysis of geological materials: implications from texture measurements at the recently upgraded neutron time-of-flight diffractometer SKAT, J. Appl. Crystallography, 2014, vol. 47, pp.1520–1534.
Kern H., P- and S-wave velocities in crustal and mantle rocks under the simultaneous action of high confining pressure and high temperature and the effect of the rock microstructure. In: Schreyer, W. (Ed.), High-Pressure Researchers in Geoscience. H. Schweizerhartsche Verlagsbuchhandlung, Stuttgart, 1982.
Kern H., Ivankina T.I., Nikitin A.N., Lokajicek T., and Pros Z., The effect of oriented microcracks and crystallographic and shape preferred orientation on bulk elastic anisotropy of a foliated biotite gneiss from Outokumpu, Tectonophysics, 2008, vol. 457, pp.143–149.
Kern H., Mengel K., Strauss K.W., Ivankina T.I., Nikitin A.N., and Kukkonen I.T., Elastic wave velocities, chemistry and modal mineralogy of crustal rocks sampled by the Outokumpu scientific drill hole: Evidence from lab measurements and modeling, Physics of the Earth and Planetary Interiors, 2009, vol. 175, pp.151–166.
Kichanov S.E., Kozlenko D.P., Ivankina T.I., Rutkauskas A.V., and Savenko B.N., The neutron imaging and tomography studies of deep-seated rocks from the Kola superdeep borehole, Physics Procedia, 2015, vol. 69, pp.537–541.
Lobanov K.V., Kazansky V.I., Kusnetsov A.V., Zharikov A.V., Nikitin A.N., Ivankina T.I., and Zamyatina N.V., Correlation of Archean rocks from the Kola superdeep borehole and their analogues from the surface: evidence from structural – petrological, petrophysical and neutron diffraction data, Petrology, 2002, vol. 10, no. 1, pp.23–38.
Lokajicek Т. and Svitek T., Laboratory measurement of elastic anisotropy on spherical rock samples by longitudinal and transverse sounding under confining pressure, Ultrasonics, 2015, vol. 56, pp. 294–302.
Melia P.J. and Carlson R.L., An experimental test of P-wave anisotropy in stratified media, Geophysics, 1984, vol. 49, pp. 364–378.
Schoenberg M. and Muir F., A calculus for finely layered anisotropic media, Geophysics, 1989, vol. 54, no. 5, pp.581–589.
Vasin R.N., Wenk H.-R., Kanitpanyacharoen W., Matthies S., and Wirth R., Elastic anisotropy modeling of Kimmeridge shale, J. Geophys. Res.: Solid Earth, 2013, vol. 118, pp.1–26.