This thesis presents the theory and the first applications of the
stress sensitivity approach for anisotropic media under arbitrary
effective stress. This approach enables a rock physical interpretation
of seismic velocity observations as a function of confining stress and
The main objective of this thesis was to validate the key aspects of
the theoretical results by analyzing stress dependent seismic velocity
observations obtained from very different rocks in ultrasonic
laboratory experiments. The stress sensitivity approach formulates the
stress dependence of velocities in terms of the variations of the dry
rock matrix compliances via stress induced variations of the pore
space geometry. The most important characteristic for the stress
dependence of various rock properties is the tensor of stress
It is shown that there are many different isotropic and anisotropic
rocks where all elastic compliances and seismic velocities in each
direction under isostatic load can be described by an equation of the form:
Γ(P) = AΓ + KΓ P - BΓexp(-DP),
where Γ is the property under consideration. The stress
sensitivity approach provides the physical meaning of the fit
parameters A, K, B, and D with respect to this rock property.
Moreover, it was found that the parameter D is a universal quantity
for all mentioned properties.
The stress sensitivity approach was applied to P- and S-wave
velocity-stress observations from different rock types. For each of
the samples it was possible to find a universal parameter D. It was
also found that for some rocks the universality of parameter D even
holds for the stress dependence of electrical resistivity.
Results derived from the analyzis of stress dependent velocity
observations on dry rocks of the KTB pilot hole were used to estimate
reflectivity pattern changes of the SE2 fault zone induced by pumping
and injection tests.