Most current seismic methods to seismically characterize fractures in tight reservoirs depend on a few anisotropic wave propagation signatures that can arise from aligned fractures. While seismic anisotropy can be a powerful fracture diagnostic, a number of situations can lessen its usefulness or introduce interpretation ambiguities. Fortunately, laboratory and theoretical work in rock physics ...

-The internal properties within and adjacent to fault zones are reviewed, principally on the basis of laboratory, borehole, and seismic refraction and reflection data. The deformation of rocks by faulting ranges from intragrain microcracking to severe alteration. Saturated microcracked and mildly fractured rocks do not exhibit a significant reduction in velocity, but, from borehole measurements...

Compressional(Vp) and shear-wave (Vs) velocities were determined within earthen levees on the Rio Grande River in south Texas, south New Mexico and New Orleans. A loosely fitting relationship was developed to better characterize the internal condition of the levees. Seismic data were incorporated with surface observations, existing core taken from the levee, and airborne EM data acquired. Sever...

This paper describes new procedures for processing data acquired with 4C seismic sensors distributed as horizontal arrays on the seafloor and seismic sources positioned either at the sea surface or on the seafloor. Two types of images can be produced from 4C seismic data: a P-P image and a P-SV (converted-shear) image. For P-P imaging, the large elevation difference between deep-water seafloor ...

Large earthquakes are sometimes observed to trigger other large earthquakes on nearby faults. The magnitudes of the calculated Coulomb stress transfers presumed to cause the triggering are 10 –10 3 of the earthquake stress drops. The earthquake stress drops and the triggering delay times are similarly small with respect to the natural recurrence time of the earthquakes. This requires that both ...

Relative travel time delays of teleseismic P and S waves, recorded during the Mantle Electromagnetic and Tomography (MELT) Experiment, have been inverted tomographically for upper-mantle structure beneath the southern East Pacific Rise. A broad zone of low seismic velocities extends beneath the rise to depths of about 200 kilometers and is centered to the west of the spreading center. The magni...

The full elastic tensors of the sheet silicates muscovite, illite-smectite, kaolinite, dickite, and nacrite have been derived with first-principles calculations based on density functional theory. For muscovite, there is excellent agreement between calculated properties and experimental results. The influence of cation disorder was investigated and found to be minimal. On the other hand, stacki...

[1] Sound velocity measurements on candidate mantle minerals at relevant mantle conditions are needed to interpret Earth’s seismic structure in terms of model abundances, variable composition, and other potentially influential parameters such as electronic spin-pairing transitions. Here the sound velocities of the lower-mantle ferropericlase have been measured by nuclear resonant inelastic X-ra...

[1] In order to examine the potential of seismology to determine the interior structure and properties of Europa, it is essential to calculate seismic velocities and attenuation for the range of plausible interiors. We calculate a range of models for the physical structure of Europa, as constrained by the satellite’s composition, mass, and moment of inertia. We assume a water-ice shell, a pyrol...

Seismic observations recorded by an African seismic array reveal a low velocity anomaly at the base of the mantle beneath the Indian Ocean, with steeply dipping edges, rapidly varying thicknesses and geometries, and anomalously low shear wave velocities decreasing from 32% at 200 km above the core^mantle boundary to 39% to 312% at the core^ mantle boundary (relative to the preliminary reference...