Seismic velocity changes caused by an overburden stress

Abstract

An increase in seismic velocity with depth is a common rock property, one that can be encountered practically everywhere. Overburden pressure increases vertical stress, producing a nonlinear elastic response. Application of a conventional nonlinear theory to this problem leads to transverse isotropy, with explicit relationships between nonlinear constants and elastic anisotropy parameters. These relationships can be used in velocity “depth trend” removal and in computing offset-dependent corrections for stacking and migration. Assumptions about small static stress and the use of linearized solutions for its evaluation are invalid for overburden problems — more accurate approximations are required. Realistic tomography models should account for elastic anisotropy as a basic feature. Our theory gives an accurate fit to well and stacking velocity data for the Los Angeles Basin. Overburden stress is a likely cause of shear-wave generation by underground explosions.

Damage Evolution and Failure Behavior of Post-Mainshock Damaged Rocks under Aftershock Effects

“…Ultrasonic P-wave velocity (UPV) technique is an effective nondestructive testing method to evaluate the inner damage state of rock [42][43][44]. Previous studies suggested that the variation of wave velocity depends on the damage extent of rocks [45,46]. In this paper, the P-wave velocity in the axial direction was monitored at the peak stress in each cycle.…”

Seismic Gradiometry using Ambient Seismic Noise in an Anisotropic Earth

“…Knowledge of the subsurface stress state and material properties is key to understanding a range of earth-scientific phenomena such as earthquake and landslide nucleation, drilling and shallow-gas hazards, induced seismicity, and many other types of deformation and material failure. Variations of stress state are known to cause concomitant variations in elastic moduli, and these properties in turn a↵ect the speed of elastic waves propagating through the medium (Brenguier et al, 2008;Korneev & Glubokovskikh, 2013;Brenguier et al, 2014;Hobiger et al, 2016). In particular, the orientation and magnitude of stress and the alignment of crystal orientation, pores, or layering, causes the wave speed to vary with direction of propagation, a property known as anisotropy (Crampin et al, 1980a;Teanby et al, 2004;Boness & Zoback, 2004;Herwanger & Horne, 2009).…”

Probabilistic analysis and comparison of stress-dependent rock physics models

“…exponential) behaviour is a consequence of a greater number of more compliant cracks at lower effective stresses. Many models have been derived to account for this non-linearity, such as empirically determined relation-Probabilistic analysis and comparison of stress-dependent rock physics models 3 ships (e.g., Zimmerman et al, 1986 ), third order elasticity theory (e.g., Prioul et al, 2004 ;Korneev & Glubokovskikh, 2013 ), Hertz-Mindlin contact forces (e.g., Makse et al, 1999 ), micro-structural models (e.g., Sayers, 2002 ;Tod, 2002 ;Hall et al, 2008 ;Sarout & Guéguen, 2008 ;Ougier-Simonin et al, 2009 ;Guéguen & Sarout, 2011 ) and relationships derived from first principles that are consistent with empirically derived equations (e.g., Shapiro, 2003 ;Shapiro, 2005 ).…”