bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal analysis of the southern Powder River Basin, Wyoming
Authors: McPherson Brian J. O. L. , Chapman David S.
Published: October 2002

Temperature and geologic data from over 3000 oil and gas wells within a 180 km × 30 km area that transect across the southern Powder River Basin in Wyoming, U.S.A., were used to determine the present thermal regime of the basin. Three‐dimensional temperature fields within the transect, based on corrected bottomhole temperatures (BHTs) and other geologic information, were assessed using: (1) A laterally constant temperature gradient model in conjunction with an [Formula: see text] norm inversion method, and (2) a laterally variable temperature gradient model in conjunction with a stochastic inversion technique. The mean geothermal gradient in the transect is 29°C/km, but important lateral variations in the geothermal gradient exist. The average heat flow for the southern Powder River Basin is [Formula: see text] with systematic variations between [Formula: see text] and [Formula: see text] along the transect. Extremely high local heat flow (values up to [Formula: see text]) in the vicinity of the Teapot Dome and the Salt Creek Anticline and low heat flow of [Formula: see text] occurring locally near the northeast end of the transect are likely caused by groundwater movement.
Analysis of anomaly correlations
Authors: von Frese Ralph R. B. , Jones Michael B. , Kim Jeong Woo , Kim Jeong‐Hee
Published: October 2002

Recognizing correlations between data sets is the basis for rationalizing geophysical interpretation and theory. Procedures are presented that constitute an effective process for identifying correlative features between two or more digital data sets. The procedures include the development of normalization factors from the mean and variance properties of the data sets. Using these factors, the data sets may be transformed so that they have common amplitude ranges, means, and variances, thereby allowing a common graphical representation of the data sets that facilitates the visualization of feature correlations. Anomaly features that show direct, inverse, or no correlations between data sets may be separated by the application of correlation filters in the frequency domains of the data sets. The correlation filter passes or rejects wavenumbers between coregistered data sets based on the correlation coefficient between common wavenumbers as given by the cosine of their phase difference. Standardizing and summing the filtered outputs where directly correlative features have been enhanced yields local favorability indices that optimize the perception of these features. Differencing the standardized outputs where inversely correlative features have been enhanced, on the other hand, provides favorability indices that improve the perception of the inverse correlations. This study includes a generic example, as well as magnetic and gravity anomaly profile examples that illustrate the usefulness of these procedures for extracting correlative features between digital data sets.
Automatic conversion of magnetic data to depth, dip, and susceptibility contrast using the SPI (TM) method
Authors: Thurston Jeffrey B. , Smith Richard S.
Published: October 2002

The Source Parameter Imaging (SPI™) method computes source parameters from gridded magnetic data. The method assumes either a 2-D sloping contact or a 2-D dipping thin‐sheet model and is based on the complex analytic signal. Solution grids show the edge locations, depths, dips, and susceptibility contrasts. The estimate of the depth is independent of the magnetic inclination, declination, dip, strike and any remanent magnetization; however, the dip and the susceptibility estimates do assume that there is no remanent magnetization. Image processing of the source‐parameter grids enhances detail and provides maps that facilitate interpretation by nonspecialists. The SPI method tests successfully on synthetic profile and gridded data. SPI maps derived from aeromagnetic data acquired over the Peace River Arch area of northwestern Canada correlate well with known basement structure and furthermore show that the Ksituan Magmatic Arc can be divided into several susceptibility subdomains.
Acoustic signatures of partial saturation
Authors: Knight Rosemary , Dvorkin Jack , Nur Amos
Published: October 2002

The relationship between elastic wave velocities and water saturation in a water/gas reservoir depends strongly on whether saturation is heterogeneous (patchy) or homogeneous. Heterogeneity in saturation may result from lithologic heterogeneity because under conditions of capillary equilibrium, different lithologies within a reservoir can have different saturations, depending on their porosities and permeabilities. We investigate this phenomenon by generating models of a reservoir in which we control the distribution of lithologic units and theoretically determine the corresponding velocity‐saturation relationship. We assume a state of capillary equilibrium in the reservoir and determine the saturation level of each region within the reservoir from the corresponding capillary pressure curve for the lithologic unit at that location. The velocities we calculate for these models show that saturation heterogeneity, caused by lithologic variation, can lead to a distinct dependence of velocity on saturation. In a water‐gas saturated reservoir, a patchy distribution of the different lithologic units is found to cause P-wave velocity to exhibit a noticeable and almost continuous velocity variation across the entire saturation range. This is in distinct contrast to the response of a homogeneous reservoir where there is only a large change in velocity at water saturations close to 100%.
Fluid migration in the vadose zone from 3-D inversion of resistivity monitoring data
Authors: Park Stephen
Published: October 2002

The movement of a small plume of fresh water through the vadose zone was monitored using surface resistivity tomography and pole‐pole potential measurements. Sets of potential measurements on a square grid at several times throughout the experiment show gradual, progressive, and systematic development of low‐resistivity zones that are inferred to be loci of fluid concentration. A procedure for inverting percentage changes in potentials is developed here and used to map maximum potential changes of 13% into resistivity decreases of up to 40% through 3-D resistivity inversion. The resulting patterns are complex, with both resistivity increases and decreases needed to match the observed data. The resistivity reductions show a spatial connection to the plume’s source and are suggestive of the fluid migration. Resistivity increases generally appear to form rims surrounding the decreases and may be artifacts of the inversion process. However, some isolated increases in the surface layer may be caused by evaporation of fluid from previous precipitation events. Interpretation of the complex patterns may limit the usefulness of this method for monitoring fluid migration. Nonetheless, the resulting pattern of resistivity reductions may show details of fluid migration that are unavailable with more conventional monitoring techniques. In this experiment, comparison of the volume with reduced resistivity with the volume of injected water predicts only a 0.5% increase in saturated porosity, demonstrating that fluid flow in the vadose zone was most likely controlled by the distribution of fine‐grained clays and silts and occurred by capillary action.
Seismic monitoring of diffraction images for detection of local heterogeneities
Authors: Landa Evgeny , Keydar Shemer
Published: October 2002

Diffracted waves contain valuable information regarding both the structure and composition of the media they are in. In seismic data processing, however, these waves are usually regarded as noise. In this paper, we present an attempt to use scattered/diffracted waves for the detection of local heterogeneities. The method is based on the detection of diffracted waves by concentrating the signal amplitudes from diffracting points on the seismic section. This is done using a correlation procedure that enhances the amplitude of the seismic signal at the location of the diffractors on the common‐diffraction‐point section (D-section). The new local time correction for diffraction traveltime curve parameterization is based on the radius of curvature of the diffracted wavefront and near‐surface velocity. We use the idea of seismic monitoring for detection and delineating local objects which may occur within the subsurface resulting from human activity or fast geological processes. The method consists of continuous repetition of seismic experiments above an investigated area, constructing D-sections, and comparing the images obtained.
Bounds on low‐frequency seismic velocities in partially saturated rocks
Authors: Mavko Gary , Mukerji Tapan
Published: October 2002

The most common technique for estimating seismic velocities in rocks with mixed pore fluid saturations is to use Gassmann’s relations with an effective fluid whose density and compressibility are averages of the individual pore fluid properties. This approach is applicable only if the gas, oil, and brine phases are mixed uniformly at a very small scale, so the different wave‐induced increments of pore pressure in each phase have time to diffuse and equilibrate during a seismic period. In contrast, saturations that are heterogeneous over scales larger than the characteristic diffusion length, i.e., patchy saturation, will always lead to higher seismic velocities than if the same fluids are mixed uniformly at a fine scale. Critical saturation scales separating uniform from patchy behavior are typically of the order 0.1–1 cm for laboratory measurements and tens of centimeters for field seismic frequencies. For low seismic frequencies, velocities corresponding to patchy and homogeneous saturations represent approximate upper and lower bounds for given saturations and dry rock properties. For well‐consolidated rocks, both bounds can be estimated easily using Gassmann’s relations with Voigt and Reuss average effective fluids, respectively.
Variation ofP-wave reflectivity with offset and azimuth in anisotropic media
Authors: Rüger Andreas
Published: October 2002

P-wave amplitudes may be sensitive even to relatively weak anisotropy of rock mass. Recent results on symmetry‐plane P-wave reflection coefficients in azimuthally anisotropic media are extended to observations at arbitrary azimuth, large incidence angles, and lower symmetry systems. The approximate P-wave reflection coefficient in transversely isotropic media with a horizontal axis of symmetry (HTI) (typical for a system of parallel vertical cracks embedded in an isotropic matrix) shows that the amplitude versus offset (AVO) gradient varies as a function of the squared cosine of the azimuthal angle. This change can be inverted for the symmetry‐plane directions and a combination of the shear‐wave splitting parameter γ and the anisotropy coefficient [Formula: see text]. The reflection coefficient study is also extended to media of orthorhombic symmetry that are believed to be more realistic models of fractured reservoirs. The study shows the orthorhombic and HTI reflection coefficients are very similar and the azimuthal variation in the orthorhombic P-wave reflection response is a function of the shear‐wave splitting parameter γ and two anisotropy parameters describing P-wave anisotropy for near‐vertical propagation in the symmetry planes. The simple relationships between the reflection amplitudes and anisotropic coefficients given here can be regarded as helpful rules of thumb in quickly evaluating the importance of anisotropy in a particular play, integrating results of NMO and shear‐wave‐splitting analyses, planning data acquisition, and guiding more advanced numerical amplitude‐inversion procedures.
Airborne gravimetry: An investigation of filtering
Authors: Childers Vicki A. , Bell Robin E. , Brozena John M.
Published: October 2002

Low‐pass filtering in airborne gravimetry data processing plays a fundamental role in determining the spectral content and amplitude of the free‐air anomaly. Traditional filters used in airborne gravimetry, the 6 × 20-s resistor‐capacitor (RC) filter and the 300-s Gaussian filter, heavily attenuate the waveband of the gravity signal. As we strive to reduce the overall error budget to the sub-mGal level, an important step is to evaluate the choice and design of the low‐pass filter employed in airborne gravimetry to optimize gravity anomaly recovery and noise attenuation. This study evaluates low‐pass filtering options and presents a survey‐specific frequency domain filter that employs the fast Fourier transform (FFT) for airborne gravity data. This study recommends a new approach to low‐pass filtering airborne data. For a given survey, the filter is designed to maximize the target gravity signal based upon survey parameters and the character of measurement noise. This survey‐specific low‐pass filter approach is applied to two aerogravimetry surveys: one conducted in West Antarctica and the other in the eastern Pacific off the California coast. A reflight comparison with the West Antarctic survey shows that anomaly amplitudes are increased while slightly improving the rms fit between the reflown survey lines when an appropriately designed FFT filter is employed instead of the traditionally used filters. A comparison of the East Pacific survey with high‐resolution shipboard gravity data indicates anomaly amplitude improvements of up to 20 mGal and a 49% improvement of the rms fit from 3.99 mGal to 2.04 mGal with the appropriately designed FFT filter. These results demonstrate that substantial improvement in anomaly amplitude and wavelength can be attained by tailoring the filter to the survey.
Reconstruction of band‐limited signals, irregularly sampled along one spatial direction
Authors: Duijndam A. J. W. , Schonewille M. A. , Hindriks C. O. H.
Published: October 2002

Seismic signals are often irregularly sampled along spatial coordinates, leading to suboptimal processing and imaging results. Least squares estimation of Fourier components is used for the reconstruction of band‐limited seismic signals that are irregularly sampled along one spatial coordinate. A simple and efficient diagonal weighting scheme, based on the distance between the samples, takes the properties of the noise (signal outside the bandwidth) into account in an approximate sense. Diagonal stabilization based on the energies of the signal and the noise ensures robust estimation. Reconstruction for each temporal frequency component allows the specification of a varying spatial bandwidth dependent on the minimum apparent velocity. This parameterization improves the reconstruction capability for the lower temporal frequencies. In practical circumstances, the maximum size of the gaps in which the signal can be reconstructed is three times the (temporal frequency dependent) Nyquist interval. Reconstruction in the wavenumber domain allows a very efficient implementation of the algorithm, and takes a total number of operations a few times that of a 2-D fast Fourier transform corresponding to the size of the output data set. Quality control indicators of the reconstruction procedure can be computed which may also serve as decision criteria on in‐fill shooting during acquisition. The method can be applied to any subset of seismic data with one varying spatial coordinate. Applied along the cross‐line direction, it can be used to compute a 3-D stack with improved anti‐alias protection and less distortion of the signal within the bandwidth.
3-D structure below Ävrö Island from high‐resolution reflection seismic studies, southeastern Sweden
Authors: Juhlin Christopher , Palm Hans
Published: October 2002

Two 1-km-long perpendicular seismic reflection lines were acquired on Ävrö Island, southeast Sweden, in October 1996 in order to (1) test the seismic reflection method for future site investigations, (2) map known fracture zones, and (3) add to the Swedish database of reflection seismic studies of the shallow crystalline crust. An east‐west line was shot with 5-m geophone and shot point spacing, and a north‐south line was shot with 10-m geophone and shotpoint spacing. An explosive source with a charge size of 100 g was used along both lines. The data clearly image three major dipping reflectors and one subhorizontal one in the upper 200 ms (600 m). The dipping reflectors (to the south, east, and north‐west) intersect or project to the surface at or close to where surface‐mapped fracture zones exist. The south‐dipping reflector correlates with the top of a heavily fractured interval observed in a borehole (KAV01) at about 400 m. The subhorizontal zone at about 100–200 m correlates with a known fracture zone in the same borehole (KAV01). 3-D effects are apparent in the data, and only where the profiles cross can the true orientation of the reflecting events be determined. To properly orient and locate all events observed on the lines requires acquisition of 3-D data.
The resolving power of seismic amplitude data: An anisotropic inversion/migration approach
Authors: de Hoop Maarten V. , Spencer Carl , Burridge Robert
Published: October 2002

A description of the theory and numerical implementation of a 3-D linearized asymptotic anisotropic inversion method based on the generalized Radon transform is given. We discuss implementation aspects, including (1) the use of various coordinate systems, (2) regularization by both spectral and Bayesian statistical techniques, and (3) the effects of limited acquisition apertures on inversion. We give applications of the theory in which well‐resolved parameter combinations are determined for particular experimental geometries and illustrate the interdependence of parameter and spatial resolutions. Procedures for evaluating uncertainties in the parameter estimates that result from the inversion are derived and demonstrated.
Focusing geophysical inversion images
Authors: Portniaguine Oleg , Zhdanov Michael S.
Published: October 2002

A critical problem in inversion of geophysical data is developing a stable inverse problem solution that can simultaneously resolve complicated geological structures. The traditional way to obtain a stable solution is based on maximum smoothness criteria. This approach, however, provides smoothed unfocused images of real geoelectrical structures. Recently, a new approach to reconstruction of images has been developed based on a total variational stabilizing functional. However, in geophysical applications it still produces distorted images. In this paper we develop a new technique to solve this problem which we call focusing inversion images. It is based on specially selected stabilizing functionals, called minimum gradient support (MGS) functionals, which minimize the area where strong model parameter variations and discontinuity occur. We demonstrate that the MGS functional, in combination with the penalization function, helps to generate clearer and more focused images for geological structures than conventional maximum smoothness or total variation functionals. The method has been successfully tested on synthetic models and applied to real gravity data.
Detection of fracture orientation using azimuthal variation ofP-wave AVO responses
Authors: Pérez Maria A. , Gibson Richard L. , Toksöz M. Nafi
Published: October 2002

Azimuthally dependent P-wave amplitude variation with offset (AVO) responses can be related theoretically to open fracture orientation and have been suggested as a geophysical tool to identify fracture orientation in fractured oil and gas reservoirs. A field experiment conducted recently over a fractured reservoir in the Barinas Basin, Venezuela provides data for an excellent test of this approach. Three lines of data were collected in three different azimuths, and three component receivers were used. The distribution of fractures in this reservoir was obtained previously using measurements of shear‐wave splitting from P-S converted waves from the same data set. In this work, we use P-wave data to see if the data can yield the same information using azimuthal variation of P-wave AVO responses. Results obtained from the azimuthal P-wave AVO analysis corroborate the fracture orientation obtained previously using P-S converted waves. This analysis with field data is an example of the high potential of P-waves to detect fracture effects on seismic wave propagation.
Eigenstructure‐based coherence computations as an aid to 3-D structural and stratigraphic mapping
Authors: Gersztenkorn Adam , Marfurt Kurt J.
Published: October 2002

Coherence measures applied to 3-D seismic data volumes have proven to be an effective method for imaging geological discontinuities such as faults and stratigraphic features. By removing the seismic wavelet from the data, seismic coherence offers interpreters a different perspective, often exposing subtle features not readily apparent in the seismic data. Several formulations exist for obtaining coherence estimates. The first three generations of coherence algorithms at Amoco are based, respectively, on cross correlation, semblance, and an eigendecomposition of the data covariance matrix. Application of these three generations to data from the Gulf of Mexico indicates that the implementation of the eigenstructure approach described in this paper produces the most robust results. This paper first introduces the basic eigenstructure approach for computing coherence followed by a comparison on data from the Gulf of Mexico. Next, Appendix A develops a theoretical connection between the well‐known semblance and the less well‐known eigenstructure measures of coherence in terms of the eigenvalues of the data covariance matrix. Appendix B further extends the analysis by comparing the semblance- and eigenstructure‐based coherence measures in the presence of additive uncorrelated noise.
Approximations to the Zoeppritz equations and their use in AVO analysis
Authors: Wang Yanghua
Published: October 2002

To efficiently invert seismic amplitudes for elastic parameters, pseudoquartic approximations to the Zoeppritz equations are derived to calculate P-P-wave reflection and transmission coefficients as a function of the ray parameter p. These explicit expressions have a compact form in which the coefficients of the p2 and p4 terms are given in terms of the vertical slownesses. The amplitude coefficients are also represented as a quadratic function of the elastic contrasts at an interface and are compared to the linear approximation used in conventional amplitude variation with offset (AVO) analysis, which can invert for only two elastic parameters. Numerical analysis with the second‐order approximation shows that the condition number of the Fréchet matrix for three elastic parameters is improved significantly from using a linear approximation. Therefore, those quadratic approximations can be used directly with amplitude information to estimate not only two but three parameters: P-wave velocity contrast, S-wave velocity contrast, and the ratio of S-wave and P-wave velocities at an interface.
Apparent AVA effects of fine layering
Authors: Wapenaar Kees , van Wijngaarden Aart‐Jan , van Geloven Wim , van der Leij Taco
Published: October 2002

The fine layering of the earth’s subsurface causes apparent amplitude‐variation‐with‐angle (AVA) effects in seismic reflection data. One can distinguish between reflection‐ and propagation‐related apparent AVA effects: the reflection of a package of thin layers is accompanied with angle‐dependent wavelet interference, whereas propagation through finely layered media causes angle‐dependent wavelet dispersion. Obviously, both types of apparent AVA effects hinder AVA inversion for the elastic parameters. Due to the band limitation of the seismic data, the reflection‐related interference effects cannot be removed. However, they can be equalized for all propagation angles by applying an angle‐dependent filter in the imaging step in angle‐dependent migration schemes. The underlying assumption is that the source function is known and that source directivity effects have been compensated prior to migration. The propagation‐related dispersion effects can be compensated for in the downward extrapolation process by means of inverse generalized primary propagators. Angle‐dependent migration, including the above mentioned modifications, yields an angle‐dependent reflectivity section in which the apparent AVA effects of fine layering are suppressed.
Scattering by hydraulic fractures: Finite‐difference modeling and laboratory data
Authors: Groenenboom Jeroen , Falk Joachim
Published: October 2002

Reservoir production can be stimulated by creating hydraulic fractures that effectively facilitate the inflow of hydrocarbons into a well. Considering the effectiveness and safety of the operation, it is desirable to monitor the size and location of the fracture. In this paper we investigate the possibilities of using seismic waves generated by active sources to characterize the fractures. First, we must understand the scattering of seismic waves by hydraulic fractures. For that purpose we use a finite‐difference modeling scheme. We argue that a mechanically open hydraulic fracture can be represented by a thin, fluid‐filled layer. The width or aperture of the fracture is often small compared to the seismic wavelength, which forces us to use a very fine grid spacing to define the fracture. Based on equidistant grids, this results in a large number of grid points and hence computationally expensive problems. We show that this problem can be overcome by allowing for a variation in grid spacing in the finite‐difference scheme to accommodate the large‐scale variation in such a model. Second, we show ultrasonic data of small‐scale hydraulic fracture experiments in the laboratory. At first sight it is difficult to unravel the interpretation of the various events measured. We use the results of the finite‐difference modeling to postulate various possible events that might be present in the data. By comparing the calculated arrival times of these events with the laboratory and finite‐difference data, we are able to propose a plausible explanation of the set of scattering events. Based on the laboratory data, we conclude that active seismic sources can potentially be used to determine fracture size and location in the field. The modeling example of fracture scattering illustrates the benefit of the finite‐difference technique with a variation in grid spacing for comparing numerical and physical experiments.
Limitations on impedance inversion of band‐limited reflection data
Authors: Ghosh Santi Kumar
Published: October 2002

A seismic approximate impedance log is often the ultimate output in the sequence of seismic data‐processing steps. In principle, the true acoustic impedance is obtainable from the inversion of full‐band impulse response. Because the seismic data necessarily is band limited, its inversion obviously would produce an approximate impedance log. A question addressed is how the true and reconstructed logs are related and a mathematical relationship between the two is derived without the assumptions required in an existing derivation of the same result. The deductions also include the contribution of an individual seismic frequency in the reconstruction of the impedance and, in particular, a simple formula for the contribution of direct‐current (dc) frequency, which never is recorded but is required to supplement the inversion. Analytical expressions are derived for the reconstructed impedance corresponding to any given frequency band for two cases: a simple discontinuity and a bed sandwiched between two similar half‐spaces. While analyzing the results, some conclusions pertinent to seismic exploration are drawn. A criterion is formulated to decide what should be termed a thin bed within a homogeneous half‐space in the context of a white band of frequencies, in contrast to a single dominant frequency, which is the basis of the Widess criterion.
Neural networks in geophysical applications
Authors: van der Baan Mirko , Jutten Christian
Published: October 2002

Neural networks are increasingly popular in geophysics. Because they are universal approximators, these tools can approximate any continuous function with an arbitrary precision. Hence, they may yield important contributions to finding solutions to a variety of geophysical applications. However, knowledge of many methods and techniques recently developed to increase the performance and to facilitate the use of neural networks does not seem to be widespread in the geophysical community. Therefore, the power of these tools has not yet been explored to their full extent. In this paper, techniques are described for faster training, better overall performance, i.e., generalization, and the automatic estimation of network size and architecture.
Electromagnetic inversion using quasi‐linear approximation
Authors: Zhdanov Michael S. , Fang Sheng , Hursán Gábor
Published: October 2002

Three‐dimensional electromagnetic inversion continues to be a challenging problem in electrical exploration. We have recently developed a new approach to the solution of this problem based on quasi‐linear approximation of a forward modeling operator. It generates a linear equation with respect to the modified conductivity tensor, which is proportional to the reflectivity tensor and the complex anomalous conductivity. We solved this linear equation by using the regularized conjugate gradient method. After determining a modified conductivity tensor, we used the electrical reflectivity tensor to evaluate the anomalous conductivity. Thus, the developed inversion scheme reduces the original nonlinear inverse problem to a set of linear inverse problems. The developed algorithm has been realized in computer code and tested on synthetic 3-D EM data. The case histories include interpretation of a 3-D magnetotelluric survey conducted in Hokkaido, Japan, and the 3-D inversion of the tensor controlled‐source audio magnetotelluric data over the Sulphur Springs thermal area, Valles Caldera, New Mexico, U.S.A.
Deconvolving the ghost effect of the water surface in marine seismics
Authors: Ghosh Santi Kumar
Published: October 2002

The ghost filters arising from the effect of the water surface on both source and receiver sides have a common time domain representation that consists of a unit impulse followed by its ghost, which is a delayed, negative unit impulse. The origin of the difficulties of deghosting lies in the zeroes in the spectrum of the ghost filter, which render incorrect any deghosting through least‐squares inverse filtering in the time domain. Another shortcoming of the time domain approach is that the digital description of the ghost filter is inexact when a sampling instant does not coincide with the instant of the onset of the ghost impulse. A frequency domain approach, on the other hand, is straightforward and accurate because it can avoid the zeroes of the filter either by explicitly choosing a recording band that excludes the zeroes or by recording at two depths. These two depths should be selected according to the criterion that their highest common measure is small enough to prevent zeroes at a common frequency of the two recordings. As the source‐side and the receiver‐side ghost filters have the same form, the criterion derived for the selection of the depths of the receivers would also hold for the selection of the depths of two sources whose aggregate signature is desired to have no zeroes in the spectrum, within the operative band. An important ramification of the analysis consists of the disproof of a prevalent conjecture that the zeroes in the spectrum of a wavelet make its autocorrelation matrix singular; actually, the zeroes cause an inexact and unacceptable least‐squares inverse, although the matrix itself is well conditioned.
Fundamentals of seismic rock physics
Authors: Wang Zhijing (Zee)
Published: October 2002

During the past 50 years or so, tremendous progress has been made in studying physical properties of rocks and minerals in relation to seismic exploration and earthquake seismology. During this period, many theories have been developed and many experiments have been carried out. Some of these theories and experimental results have played important roles in advancing earth sciences and exploration technologies. This tutorial paper attempts to summarize some of these results.
GRAVITY AND MAGNETIC CALCULATIONS
Authors: Nettleton L. L.
Published: October 2002

In the earlier geophysical literature, many schemes were published for the calculation of gravity and magnetic effects. For the most part these were either the curves for the effects of certain definite geometric bodies or various charts and diagrams by which the effects for a body of any shape could be determined graphically. It is probable that these schemes have had comparatively little actual application in the interpretation of magnetic and gravity surveys. This is because of the fact that unless certain controls other than the gravity and magnetic data are available the inherent ambiguities of the physically possible distributions of material which can produce the observed effects make an accurate calculation meaningless, even though the geophysical data may be of any desired precision. Furthermore, it is often possible to calculate, from rather generalized forms, geophysical effects which are in agreement with those observed within the precision of the observations. In fact, unless two conditions are fulfilled, i.e., (1) observed data are of high precision and spaced at distances substantially less than the horizontal dimensions or depth of the disturbing body, and (2) some other control is available, there is little point to using any of the more refined methods of calculation.
Permeability characterization of the Soultz and Ogachi large‐scale reservoir using induced microseismicity
Authors: Audigane Pascal , Royer Jean‐Jacques , Kaieda Hideshi
Published: October 2002

Hydraulic fracturing is a common procedure to increase the permeability of a reservoir. It consists in injecting high‐pressure fluid into pilot boreholes. These hydraulic tests induce locally seismic emission (microseismicity) from which large‐scale permeability estimates can be derived assuming a diffusion‐like process of the pore pressure into the surrounding stimulated rocks. Such a procedure is applied on six data sets collected in the vicinity of two geothermal sites at Soultz (France) and Ogachi (Japan). The results show that the method is adequate to estimate large‐scale permeability tensors at different depths in the reservoir. Such an approach provides permeability of the medium before fracturing compatible with in situ measurements. Using a line source formulation of the diffusion equation rather than a classical point source approach, improvements are proposed for accounting in situation where the injection is performed on a well section. This technique applied to successive fluid‐injection tests indicates an increase in permeability by an order of magnitude. The underestimates observed in some cases are attributed to the difference of scale at which the permeability is estimated (some 1 km3corresponding to the seismic active volume of rock compared to a few meters around the well for the pumping or pressure oscillation tests). One advantage of the proposed method is that it provides permeability tensor estimates at the reservoir scale.
Seismic structure of basalt flows from surface seismic data, borehole measurements, and synthetic seismogram modeling
Authors: Fliedner Moritz M. , White Robert S.
Published: October 2002

We use the wide‐angle wavefield to constrain estimates of the seismic velocity and thickness of basalt flows overlying sediments. Wide angle means the seismic wavefield recorded at offsets beyond the emergence of the direct wave. This wide‐angle wavefield contains arrivals that are returned from within and below the basalt flows, including the diving wave through the basalts as the first arrival and P‐wave reflections from the base of the basalts and from subbasalt structures. The velocity structure of basalt flows can be determined to first order from traveltime information by ray tracing the basalt turning rays and the wide‐angle base‐basalt reflection. This can be refined by using the amplitude variation with offset (AVO) of the basalt diving wave. Synthetic seismogram models with varying flow thicknesses and velocity gradients demonstrate the sensitivity to the velocity structure of the basalt diving wave and of reflections from the base of the basalt layer and below. The diving‐wave amplitudes of the models containing velocity gradients show a local amplitude minimum followed by a maximum at a greater range if the basalt thickness exceeds one wavelength and beyond that an exponential amplitude decay. The offset at which the maximum occurs can be used to determine the basalt thickness. The velocity gradient within the basalt can be determined from the slope of the exponential amplitude decay. The amplitudes of subbasalt reflections can be used to determine seismic velocities of the overburden and the impedance contrast at the reflector. Combining wide‐angle traveltimes and amplitudes of the basalt diving wave and subbasalt reflections enables us to obtain a more detailed velocity profile than is possible with the NMO velocities of small‐offset reflections. This paper concentrates on the subbasalt problem, but the results are more generally applicable to situations where high‐velocity bodies overlie a low‐velocity target, such as subsalt structures.
First-Line Treatment With Epirubicin and Vinorelbine in Metastatic Breast Cancer
Authors: Vici Patrizia , Colucci Giuseppe , Gebbia Vittorio , Amodio Antonella , Giotta Francesco , Belli Franca , Conti Francesca , Gebbia Nicola , Pezzella Giuseppe , Valerio Maria Rosaria , Brandi Mario , Pisconti Salvatore , Durini Ernesto , Giannarelli Diana , Lopez Massimo
Published: October 2002

PURPOSE: This phase II multicenter trial was aimed at investigating the activity of epirubicin-vinorelbine combination as first-line chemotherapy in metastatic breast cancer patients.

PATIENTS AND METHODS: Ninety-seven patients with metastatic breast cancer and no prior exposure to anthracyclines received the following regimen: epirubicin 100 mg/m2 by intravenous (IV) bolus infusion on day 1 plus vinorelbine 25 mg/m2 by 30-minute IV infusion on days 1 and 5, every 3 weeks for up to eight cycles. All patients also received granulocyte colony-stimulating factor (G- CSF) on days 7 to 12 of every cycle.

RESULTS: Objective responses, confirmed at least 4 weeks after the first documentation, were observed in 65 out of 92 assessable patients (70.6%; 95% CI, 62% to 80%). Disease remained stable in 17 patients (18.5%). Responses were observed in all disease sites, being 94% in soft tissue, 60% in bone, and 66% in visceral disease. Median time to response, median duration of response, median time to progression, and median overall survival were 2, 9, 10, and 26 months, respectively. The dose-limiting toxicity was neutropenia, which was grade 4 in 36% of the patients, and was accompanied by fever in 26% of the cases. Grade 3 to 4 mucositis was encountered in 28% of the patients. Other toxicities were mild to moderate. No cardiotoxicity was observed.

CONCLUSION: The epirubicin-vinorelbine combination with G-CSF support has been shown in this study to be highly active as first-line treatment of metastatic breast cancer patients, with significant although transient toxicity. This justifies further evaluation in the neoadjuvant setting and in early-stage breast cancer.
Superior Survival With Capecitabine Plus Docetaxel Combination Therapy in Anthracycline-Pretreated Patients With Advanced Breast Cancer: Phase III Trial Results
Authors: O’Shaughnessy Joyce , Miles David , Vukelja Svetislava , Moiseyenko Vladimir , Ayoub Jean-Pierre , Cervantes Guadalupe , Fumoleau Pierre , Jones Stephen , Lui Wing-Yiu , Mauriac Louis , Twelves Chris , Van Hazel Guy , Verma Shailendra , Leonard Robert
Published: October 2002

PURPOSE: Docetaxel and capecitabine, a tumor-activated oral fluoropyrimidine, show high single-agent efficacy in metastatic breast cancer (MBC) and synergy in preclinical studies. This international phase III trial compared efficacy and tolerability of capecitabine/docetaxel therapy with single-agent docetaxel in anthracycline-pretreated patients with MBC.

PATIENTS AND METHODS: Patients were randomized to 21-day cycles of oral capecitabine 1,250 mg/m2 twice daily on days 1 to 14 plus docetaxel 75 mg/m2 on day 1 (n = 255) or to docetaxel 100 mg/m2 on day 1 (n = 256).

RESULTS: Capecitabine/docetaxel resulted in significantly superior efficacy in time to disease progression (TTP) (hazard ratio, 0.652; 95% confidence interval [CI], 0.545 to 0.780; P = .0001; median, 6.1 v 4.2 months), overall survival (hazard ratio, 0.775; 95% CI, 0.634 to 0.947; P = .0126; median, 14.5 v 11.5 months), and objective tumor response rate (42% v 30%, P = .006) compared with docetaxel. Gastrointestinal side effects and hand-foot syndrome were more common with combination therapy, whereas myalgia, arthralgia, and neutropenic fever/sepsis were more common with single-agent docetaxel. More grade 3 adverse events occurred with combination therapy (71% v 49%, respectively), whereas grade 4 events were slightly more common with docetaxel (31% v 25% with combination).

CONCLUSION: The significantly superior TTP and survival achieved with the addition of capecitabine to docetaxel 75 mg/m2, with the manageable toxicity profile, indicate that this combination provides clear benefits over single-agent docetaxel 100 mg/m2. Docetaxel/capecitabine therapy is an important treatment option for women with anthracycline-pretreated MBC.
Overexpression of the Polycythemia Rubra Vera-1 Gene in Essential Thrombocythemia
Authors: Teofili Luciana , Martini Maurizio , Luongo Myriam , Di Mario Antonella , Leone Giuseppe , De Stefano Valerio , Larocca Luigi Maria
Published: October 2002

PURPOSE: To examine the utility of polycythemia rubra vera-1 (PRV-1)–specific reverse transcriptase polymerase chain reaction (RT-PCR) to discriminate essential thrombocythemia (ET) and polycythemia vera (PV) from secondary thrombocytosis (ST) or secondary erythrocytosis (SE).

PATIENTS AND METHODS: We analyzed the expression of PRV-1 in granulocytes isolated from 37 patients with ET, 37 patients with PV, 25 patients with ST, 10 patients with SE, 25 patients with secondary leukocytosis (SL), five patients with chronic myelogenous leukemia (CML), five patients with chronic idiopathic myelofibrosis (IM), five patients with myelodysplastic syndrome (MDS), and 20 normal individuals by PRV-1–specific RT-PCR. In female patients, PRV-1 expression was correlated with clonality analysis as assessed by the human androgen receptor polymorphism assay.

RESULTS: PRV-1 was not expressed in granulocytes isolated from normal individuals or from patients with ST, SE, CML, IM, MDS, and inflammatory/infectious SL. On the contrary, all ET patients, 35 of 37 PV patients, and five patients with acute postsurgery and posttraumatic SL overexpressed PRV-1. All the cases with monoclonal hematopoiesis (17 of 21 with ET and 12 of 12 with PV) expressed PRV-1, yet PRV-1 overexpression extended also over the cases of ET showing polyclonal hematopoiesis (four of 20).

CONCLUSION: The overexpression of PRV-1 seems to be a useful tool for discriminating ET and PV from ST and SE, thus offering an innovative diagnostic approach on the basis of the detection of positive diagnostic criteria instead of exclusion criteria.
VAMP and Low-Dose, Involved-Field Radiation for Children and Adolescents With Favorable, Early-Stage Hodgkin’s Disease: Results of a Prospective Clinical Trial
Authors: Donaldson Sarah S. , Hudson Melissa M. , Lamborn Kathleen R. , Link Michael P. , Kun Larry , Billett Amy Louise , Marcus Karen C. , Hurwitz Craig A. , Young Jeffrey A. , Tarbell Nancy J. , Weinstein Howard J.
Published: October 2002

PURPOSE: To evaluate outcome and assess toxicity of children and adolescents with early-stage, favorable Hodgkin’s disease treated with vinblastine, doxorubicin, methotrexate, and prednisone (VAMP) and low-dose, involved-field radiation.

PATIENTS AND METHODS: One hundred ten patients with clinical stages I and II, favorable (nonbulky) Hodgkin’s disease were treated with four cycles of VAMP chemotherapy and 15 Gy involved-field radiation for those who achieved a complete response, or 25.5 Gy for those who achieved a partial response to two cycles of VAMP.

RESULTS: With a median follow-up of 5.6 years (range, 1.1 to 10.4 years), the 5-year survival and event-free survival were 99% (lower confidence limit [CL], 97.4%) and 93% (lower CL, 88.6%), respectively. Factors associated with event-free survival of 100% were complete response to two cycles of VAMP and histology other than nodular sclerosing Hodgkin’s disease (NSHD). No serious early or late toxicity has been observed. Patients presenting with clinical stages I and IIA, nonbulky disease involving fewer than three nodal sites have a projected survival and event-free survival of 100% and 97% (lower CL, 93%), respectively, at 5 years.

CONCLUSION: Risk-adapted, combined-modality therapy using only four cycles of VAMP chemotherapy with 15 to 25.5 Gy of involved-field radiation for patients with early-stage/favorable Hodgkin’s disease is highly effective and without demonstrable late effects. These results indicate that pediatric patients with stages I and II favorable Hodgkin’s disease can be cured with limited therapy that does not include an alkylating agent, bleomycin, etoposide, or high-dose, extended-field radiation therapy.
On the convergence to stationarity of birth-death processes
Authors: Coolen-Schrijner Pauline , Van Doorn Erik A.
Published: October 2002

Taking up a recent proposal by Stadje and Parthasarathy in the setting of the many-server Poisson queue, we consider the integral ∫0∞[limu→∞E(X(u))-E(X(t))]dt as a measure of the speed of convergence towards stationarity of the process {X(t), t≥0}, and evaluate the integral explicitly in terms of the parameters of the process in the case that {X(t), t≥0} is an ergodic birth-death process on {0,1,….} starting in 0. We also discuss the discrete-time counterpart of this result, and examine some specific examples.
Some peculiarities of exponential random variables
Authors: Litvak Nelly
Published: October 2002

In this paper we utilize a particular transformation of i.i.d. exponential random variables to derive two distributional identities. Throughout the analysis we discover some peculiar properties of exponentials. We also discuss possible generalizations and applications of the results.
Transient analysis of state-dependent queueing networks via cumulant functions
Authors: Matis Timothy I. , Feldman Richard M.
Published: October 2002

A new procedure that generates the transient solution of the first moment of the state of a Markovian queueing network with state-dependent arrivals, services, and routeing is developed. The procedure involves defining a partial differential equation that relates an approximate multivariate cumulant generating function to the intensity functions of the network. The partial differential equation then yields a set of ordinary differential equations which are numerically solved to obtain the first moment.
Availability analysis of periodically inspected systems with random walk model
Authors: Cui Lirong , Xie M.
Published: October 2002

In this paper, the instantaneous availability of a system maintained under periodic inspection is investigated using random walk models. Two cases are considered. In the first model, the system is repaired or modified and it is assumed to be as good as new upon periodic inspection and maintenance. In the second model, the system is not modified after the inspection if the system is still working, and the condition of the system is assumed to be the same as that before the inspection. For both models the failures only can be found through the inspection. Perfect repair or replacement of a failed system is assumed to be carried out, but the time it takes can be constant or of a random length. The relationship between this problem and the random walk model in a two-dimensional plane is described. Several new results are also shown.