VELOCITY AND ATTENUATION OF P WAVES IN SANDSTONE AS A FUNCTION OF STRAIN AMPLITUDE: LABORATORY EXPERIMENTS
B.V. Pashkov and E.I. Mashinskii
Institute of Geophysics, Siberian Branch of the RAS, 3 prosp. Akad. Koptyuga, Novosibirsk, 630090, Russia
Keywords: Nonelasticity, hysteresis, strain-amplitude dependence of velocity and attenuation, nonlinear seismics
Pages: 407-411
Abstract
The reported laboratory experiments of cycling measurements investigate strain-amplitude dependence of compressional velocity and attenuation of acoustic waves ( f ~ 1 MHz) in samples of the Nivagal sandstone. Strain-amplitude growth in a range of εd ~ (0,3-2) · 10-6 causes a 0.6% velocity increase and an up to 10% decrease in attenuation. Attenuation curves show a minor hysteresis in a full cycle (Amin → Amax → Amin). Amplitude dependence of velocity and attenuation can be better resolved at higher strains. Attenuation is more sensitive to strain variations than velocity. The revealed relationships are useful as an additional criterion in imaging sandstone formations.
|