Analysis of thomsen parameters for finely layered VTI media

Conference · Tue Apr 01 04:00:00 EST 1997

OSTI ID:303869

Berryman, J G; Berge, P A

The range of Thomsen`s anisotropy parameters {epsilon} and {delta} for vertical transversely isotropic (VTI) media when the anisotropy is due to fine layering of isotropic elas-tic materials is considered. We show that {epsilon} lies in the range -3/8 {<=} {epsilon} {<=} {1/2}[-1], for finely lay-ered media having constant density; smaller positive and all negative values of {epsilon} occur for media with large fluctuations in the Lam{acute e} parameter {lambda} We show that sign({delta}) = sign ( - ) for constant density media, so {delta} can be either positive or negative. Among all theoretically possible random media, posi-tive and negative {delta} are equally likely in finely layered media limited to two types of constituent layers. Lay-ered media having large fluctuations in Lam{acute e} {lambda} are the ones most likely to have positive {delta}. Since Gassmann`s results for fluid-saturated porous media show that the effects of fluids influence only the {lambda} Lam{acute e} constant, not the shear modulus {mu}, these results suggest that positive {delta} occurring together with positive but small {epsilon} may be indicative of changing fluid content in layered earth.

• Research Organization: Lawrence Livermore National Lab., CA (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 303869
• Report Number(s): UCRL-JC--127249; CONF-971111--; ON: DE98050929
• Country of Publication: United States
• Language: English

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