Seismic Waves Research Papers - Academia.edu (original) (raw)

A predrill estimate of pore pressure can be obtained from seismic velocities using a velocity-to–pore-pressure transform, but the seismic velocities need to be derived using methods having sufficient resolution for well planning purposes.... more

A predrill estimate of pore pressure can be obtained from seismic velocities using a velocity-to–pore-pressure transform, but the seismic velocities need to be derived using methods having sufficient resolution for well planning purposes. For a deepwater Gulf of Mexico example, significant differences are found between the velocity field obtained using reflection tomography and that obtained using a conventional method based on the Dix equation. These lead to significant differences in the predicted pore pressure. Parameters ...

This paper aims to improve current understanding of the subsurface fracture system in the Coso geothermal field, located in east-central California. The Coso reservoir is in active economic development, so that knowledge of the subsurface... more

This paper aims to improve current understanding of the subsurface fracture system in the Coso geothermal field, located in east-central California. The Coso reservoir is in active economic development, so that knowledge of the subsurface fracture system is of vital importance for an accurate evaluation of its geothermal potential and day-to-day production. To detect the geometry and density of fracture systems we applied the shear-wave splitting technique to a large number of high-quality seismograms from local microearthquakes recorded by a permanent, 16-station, down-hole, 3-component seismic array running at 480 samples/s. The analysis of shear-wave splitting (seismic birefringence) provides parameters directly related to the strike of the subsurface fractures and their density (number of cracks per unit volume), and, consequently, is an important technique to outline zones of high permeability. Three major fracture directions N10–30W, N0–20E, and N40–50E, of which the first and the second are the most prominent, were identified from the seismograms recorded by the 16-station down-hole array. All orientations are consistent with the known strike of local sets of faults and fractures in local wells and at the surface, as well as with previous analyses of seismic anisotropy in the region. The high quality of the recordings has allowed us to launch an unprecedented investigation into the characteristics of the temporal variations in crack polarization and crack density in a producing geothermal environment. Preliminary results point to significant temporal changes in shear-wave time delays, probably influenced by temporal changes in crack density within a period of 5 years (1996–2000). They are tentatively interpreted as due to a local ∼3% increase in shear-wave velocity in the southwestern part of the field during 1999.

The magnitude 7.3 Landers earthquake of 28 June 1992 triggered a remarkably sudden and widespread increase in earthquake activity across much of the western United States. The triggered earthquakes, which occurred at distances up to 1250... more

The magnitude 7.3 Landers earthquake of 28 June 1992 triggered a remarkably sudden and widespread increase in earthquake activity across much of the western United States. The triggered earthquakes, which occurred at distances up to 1250 kilometers (17 source dimensions) from the Landers mainshock, were confined to areas of persistent seismicity and strike-slip to normal faulting. Many of the triggered areas also are sites of geothermal and recent volcanic activity. Static stress changes calculated for elastic models of the earthquake appear to be too small to have caused the triggering. The most promising explanations involve nonlinear interactions between large dynamic strains accompanying seismic waves from the mainshock and crustal fluids (perhaps including crustal magma).

The purpose of blasting operations is rock fragmentation. Blasting is a key component in the overall rock fragmentation system - the first element of the ore extraction process. It provides appropriate rock material granulation or size... more

The purpose of blasting operations is rock fragmentation. Blasting is a key component in the overall rock fragmentation system - the first element of the ore extraction process. It provides appropriate rock material granulation or size that is suitable for loading and transportation. However, in spite of many advantages explosives have, their usage may cause environmental problem such as seismic vibration. One of the solutions to this particular problem may be application of an artificial screen as a barrier to the seismic wave path. The results of experimental research on the artificial screen concept, its characteristics and role in attenuation of seismic effects generated by blasting are presented. The experiment is based on two physical phenomena: (1) the size and degree of discontinuity and (2) the reflection and refraction of seismic waves. More than 1,500 laboratory measurements were conducted with different combinations of screen sizes, positions of the screen to blasting source, and intensities of blasting impulses. The results of the study show reduction of generated vibrations up to 58% by employment of artificial screens.

Computerized evaluation of Vibroseis similarity test data is the logical consequence of the increasing quality requirements for signal reproducibility and for synchronization of vibrators. The differences in start time and phase as well... more

Computerized evaluation of Vibroseis similarity test data is the logical consequence of the increasing quality requirements for signal reproducibility and for synchronization of vibrators. The differences in start time and phase as well as an indication of local phasing problems between any two Vibroseis signals can be obtained from an analysis of the difference of their respective phase spectra. This method appears to be accurate and stable with respect to harmonics which usually plague the signals from transducers monitoring the motion of the vibrators'base plates.

A compilation of compressional-wave (Vp) and shear-wave (Vs) velocities and densities for a wide variety of common lithologies is used to define new nonlinear, multivalued, and quantitative relations between these properties for the... more

A compilation of compressional-wave (Vp) and shear-wave (Vs) velocities and densities for a wide variety of common lithologies is used to define new nonlinear, multivalued, and quantitative relations between these properties for the Earth’s crust. Wireline borehole logs, vertical seismic profiles, laboratory measurements, and seismic tomography models provide a diverse dataset for deriving empirical relations between crustal Vp and Vs. The proposed Vs as a function of Vp relations fit Vs and Vp borehole logs in Quaternary alluvium and Salinian granites as well as laboratory measurements over a 7-km/sec-wide range in Vp. The relations derived here are very close to those used to develop a regional 3D velocity model for southern California, based on pre-1970 data, and thus provide support for that model. These data, and these relations, show a rapid increase in Vs as Vp increases to 3.5 km/sec leading to higher shear-wave velocities in young sedimentary deposits than commonly assumed. These relations, appropriate for active continental margins where earthquakes are prone to occur, suggests that amplification of strong ground motions by shallow geologic deposits may not be as large as predicted by some earlier models.

Упругие волны это векторные волны смещений материальных точек. В отличии от элек-тромагнитных волн они могут быть и поперечными и продольными. Обычно для них записывают разные уравнения. Здесь такого разделения не будет. При наличии... more

Упругие волны это векторные волны смещений материальных точек. В отличии от элек-тромагнитных волн они могут быть и поперечными и продольными. Обычно для них записывают разные уравнения. Здесь такого разделения не будет. При наличии поверхно-сти раздела между двумя разными средами граничные условия определяются не самими уравнениями, а некоторыми дополнительными условиями. Большой интерес представля-ют поверхностные волны, особенно в связи с землетрясениями, а также волны в анизо-тропных средах. Здесь так же, как в электродинамике, удается построить решения в виде плоских волн, что облегчает исследование процессов отражения от упругих пластин. 6.1 Упругие волны в изотропных средах В теории упругости основным объектом является вектор смещения u(r, t) точки r в мо-мент времени t. Компоненты вектора смещения u j (r, t) определяются с помощью уравне-ния ρ ∂ 2 u j (r, t) ∂t 2 = ∂σ jk (r,

GeoScienceWorld Quick search. Advanced search. GSW Home; Search: Advanced search; Geographic search; Search charts, figures, and tables. Browse: By geography; By journal; By publisher; By subject; By time. My Tools: Email alerts; My... more

GeoScienceWorld Quick search. Advanced search. GSW Home; Search: Advanced search; Geographic search; Search charts, figures, and tables. Browse: By geography; By journal; By publisher; By subject; By time. My Tools: Email alerts; My favorite journals. Information and Services: About GeoScienceWorld; About GeoRef; Content in GSW; Information for subscribers; Information for publishers; User help; Contact us. Reviews in Mineralogy and Geochemistry. Skip to main page content. ...

The main scientific and engineering goal of this book is to deal simultaneously with soil dynamics/vibrations and wave propagation in soils (including seismic waves). These various fields are generally considered separately and the... more

The main scientific and engineering goal of this book is to deal simultaneously with soil dynamics/vibrations and wave propagation in soils (including seismic waves). These various fields are generally considered separately and the important links between them, both from scientific and practical points of view, are unfortunately not investigated. They are usually considered in separate disciplines such as earthquake geotechnical engineering, civil engineering, mechanics, geophysics, seismology, numerical modelling, etc. The objective of the book is to offer in a single publication an overview of soil dynamics and wave propagation in soils with emphasis on engineering applications. It starts from a wide variety of practical problems (e.g. traffic induced vibrations, dynamic compaction, vibration isolation), then deals with 1D and 2D/3D wave propagation in heterogeneous and attenuating media (with application to laboratory and in situ dynamic characterization of soils), gives an overview of various numerical methods (e.g. FEM, BEM) to simulate wave propagation (including numerical errors, radiation/absorbing conditions, etc) and finally investigates seismic wave propagation and amplification in complex geological structures (e.g. irregular topographies, alluvial deposits).

A review of the more important aspects of geology with respect to petrophysics. A concise description of the origins of the principle types of sedimentary rocks associated with petroleum that supply the reserves for petroleum is provided.... more

A review of the more important aspects of geology with respect to petrophysics. A concise description of the origins of the principle types of sedimentary rocks associated with petroleum that supply the reserves for petroleum is provided. This is followed by theories on the origins of petroleum hydrocarbons, their migrations (sometimes over unusually long distances) to geologic traps where they establish the reservoirs of petroleum. The chapter ends with a discussion of the nature of the subsurface environments where petroleum is found and the properties and chemistry of petroleum and its products.

Classical analysis of seismic soil-structure interaction phenomena for the design of civil engineering structures and lifelines are based on two simplifying assumptions~: lateral homogeneity of the soil underneath the foundation and... more

Classical analysis of seismic soil-structure interaction phenomena for the design of civil engineering structures and lifelines are based on two simplifying assumptions~: lateral homogeneity of the soil underneath the foundation and representation of the ground motion (free field) as a pulse train of vertically or obliquely incident plane waves. For large structures founded on flexible spread footings, these hypotheses are not valid any longer. Furthermore, data recorded after the installation of dense seismograph arrays have shown that seismic ground motions can have a strong spatial variability, even over short distances and irrespective of deterministic wave passage effects. We develop in this thesis some theoretical tools for the modelization and numerical analysis of the influence of the free field and soil spatial varibilities on the structural response. A probabilistic approach is chosen, and the structural response of interest is given by an integral formulation which considers these two aspects simultaneously. Relevancy of numerical implementations are enhanced by introducing a spectral reduction of the random dimension of the fluctuating part - large or small - of the uncertain soil mechanical parameters through its Karhunen-Loeve expansion. This technique is applied to the free field as well. The numerical results obtained for various realistic cases display some specific features whose consideration seems essential in the process of industrial design. Notably, some usefull trends and sensitivity of the structural response with the free field and soil spatial variabilities are derived.

The central issue for pillar design in underground coal mining is the in situ uniaxial compressive strength (σ cm). The paper proposes a new method for estimating in situ uniaxial compressive strength in coal seams based on laboratory... more

The central issue for pillar design in underground coal mining is the in situ uniaxial compressive strength (σ cm). The paper proposes a new method for estimating in situ uniaxial compressive strength in coal seams based on laboratory strength and P wave propagation velocity. It describes the collection of samples in the Bonito coal seam, Fontanella Mine, southern Brazil, the techniques used for the structural mapping of the coal seam and determination of seismic wave propagation velocity as well as the laboratory procedures used to determine the strength and ultrasonic wave velocity. The results obtained using the new methodology are compared with those from seven other techniques for estimating in situ rock mass uniaxial compressive strength. Le problème central pour le dimensionnement des piliers d’une mine souterraine de charbon est la résistance in situ à la compression simple (σcm). L’article propose une nouvelle méthode pour estimer la résistance in situ à la compression simple de veines de charbon, basée sur des mesures de résistance au laboratoire et sur la mesure des vitesses de propagation des ondes P. L’article décrit la prise d’échantillons au niveau de la veine de charbon de Bonito, dans la mine de Fontanella, dans une région du sud-ouest du Brésil, les techniques utilisées pour la cartographie structurale des veines de charbon, la détermination des vitesses sismiques ainsi que les procédures de laboratoire utilisées pour déterminer la résistance mécanique et la vitesse des ondes ultrasoniques. Les résultats obtenus à partir de cette nouvelle approche sont comparés à ceux correspondant à sept autres méthodes d’estimation de la résistance in situ à la compression simple.

Abundant gold deposits are distributed along the margins of the North China Craton (NCC). Occurring throughout the Precambrian basement and located in or proximal to Mesozoic granitoids, these deposits show a consistent spatial–temporal... more

Abundant gold deposits are distributed along the margins of the North China Craton (NCC). Occurring throughout the Precambrian basement and located in or proximal to Mesozoic granitoids, these deposits show a consistent spatial–temporal association with Late Jurassic–Early Cretaceous magmatism and are characterized by quartz lode or disseminated styles of mineralization with extensive alteration of wall rock. Their ages are mainly