the mixture of natural and artificial seismic sources with random distributions cause diffuse wave field with random amplitudes and phases called noise. when noise is analyzed in a long-term process, it contains surface waves which are spread in all directions. thus, ambient noise contains data relevant to the surface waves. in recent years, as broadband seismic networks have been distributed v...

Analysis of the refracted arrivals on a seismic reflection profile recorded along the wall of a tunnel at an iron mine near Thabazimbi, South Africa, shows variations in P-wave velocity in dolomite away from the de-stressed zone that vary between 4.4 and 7.2 kmrs, though values greater than 5.8 kmrs predominate along most of the profile. The seismic velocities at the tunnel wall, however, vary ...

An ever present goal of seismic processing and inversion is to extract meaningful geology information from seismic data. The simplest possibility is to invert for seismic impedances, or, considering density constant, invert for velocities. Here I use a micro genetic algorithm program to achieve this goal. I use a real sonic log to compute a synthetic seismic trace and then use that trace as inp...

Mapping, localization, and general characterization of problems in reservoir fracture systems is one of the most important in oil, gas, and geothermal energy production. One way to study and monitor these fracture systems is to analyze the microearthquakes triggered during hydraulic fracturing or stimulation, as these events generally occur along newly created and preexisting fractures. Thus, t...

The objective was to build an efficient algorithm 1 to estimate seismic velocity from time-migration velocity, and 2 to convert time-migrated images to depth. We established theoretical relations between the time-migration velocity and seismic velocity in two and three dimensions using paraxial ray-tracing theory. The relation in two dimensions implies that the conventional Dix velocity is the ...

Anisotropy parameters are obtained by anisotropic velocity analysis performed on Blackfoot P-wave reflection-seismic data, in combination with sonic-log data. First, the line was processed with ProMAX seismic data-processing software using a sequence of conventional algorithms without taking anisotropy into account, in order to choose proper analysis points and horizons with confidence. Then, a...

the stolt (f-k) migration algorithm is a direct (i.e. non-recursive) fourier-domain technique based on a change of variables (or equivalently, a mapping) that converts the input spectrum to the output spectrum. the algorithm is simple and efficient but limited to constant velocity. a v(z)(f-k) migration method, capable of very high accuracy for vertical variations of velocity, can be formulated...

A new approach to seismic migration formalizes the classical diffraction (or common-tangent) stack by relating it to linearized seismic inversion and the generalized Radon transform. This approach recasts migration as the problem of reconstructing the earth’s acoustic scattering potential from its integrals over isochron surfaces. The theory rests on a solution of the wave equation with the geo...

Estimating an accurate velocity model is crucial for seismic imaging to obtain a good understanding of the subsurface structure. The objective of this thesis is to investigate methods of velocity analysis by optimizing seismic images. A conventional seismic image is obtained by zero-lag crosscorrelation of wavefields extrapolated from a source wavelet and recorded data on the surface using a ve...