Laboratory study of 3D velocity distribution of P and S wawes in rocks: comparison of high pressure study and texture based calculated data

0444546 - GLÚ 2016 RIV CA eng C - Konferenční příspěvek (zahraniční konf.)
Lokajíček, Tomáš - Svitek, Tomáš - Ivankina, T. - Kern, H.
Laboratory study of 3D velocity distribution of P and S wawes in rocks: comparison of high pressure study and texture based calculated data.
Innovations in Applied and Theoretical Rock Mechanics. Montréal: Canadian Institute of Mining, Metallurgy and Petroleum, 2015. ISBN 978-1-926872-25-4.
[International Congress of Rock Mechanics /13./. Montréal (CA), 10.05.2015-13.05.2015]
Grant CEP: GA ČR(CZ) GAP104/12/0915; GA ČR GA13-13967S; GA MŠMT LH13102
Institucionální podpora: RVO:67985831
Klíčová slova: velocity measurements * 3D-velocity calculation * neutron diffraction * seismic anisotropy * measured and calculated elastic properties
Kód oboru RIV: DC - Seismologie, vulkanologie a struktura Země

The knowledge of 3D velocity distribution of P- and S-waves in rocks is very important parameter for interpretation and understanding the nature of seismic anisotropy observed in the earth’s crust and upper mantle. A new high-pressure measuring head was designed and constructed to enable ultrasonic sounding of spherical rock samples in 132 independent directions under up to 60 MPa of acting hydrostatic pressure by means of simultaneous longitudinal and transversal sounding. New measuring system enables ultrasonic sounding of spherical rock samples by using a pair of P-wave sensors and two pairs of perpendicularly polarized S-wave sensors (TV and TH) see Fig.1. Shear wave sensors polarization is oriented according to rotation axis of the sample. An isotropic glass sphere was used to check and calibrate the new measuring setup. A spherical sample of a biotite gneiss from the Outokumpu was used for testing measurement. There is shown that both, P- and S-wave velocities, can be measured simultaneously up to 70 MPa, respectively. We report data of the 3D velocity distribution of P- and Swaves measured for the first time on a sample sphere of biotite gneiss. We rely, in particular, on the directional dependence of compressional and shear wave propagation and their relationship to the crystallographic (CPO) and shape preferred orientation (SPO) of major rock-forming minerals. The 3D seismic measurements revealed a strong foliation-related directional dependence (anisotropy) of P- and Swave velocities. Ultrasonic measurements were compared with 3D velocity calculations based on neutron diffraction measurements of crystallographic preferred orientation (CPO) of major minerals. Comparison of 3-D velocity distribution (P, S1, S2 and S1-S2) determined by two completely different methods ultrasonic sounding and neutron diffraction is presented. Measurements showed that the intrinsic bulk anisotropy is basically caused by the CPO of biotite.
Trvalý link: http://hdl.handle.net/11104/0247055