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Hybrid solution for wave propagation problems in inhomogenous media
226A obtained from over 2000 points. Using computers, it is possible to display geological profiles of the area and depth to exceed a specified N count. By mapping soft beds and basements, a useful planning tool has been developed.
885190 Engineering geological mapping for seismic microzonation Gomes Coelho, A Proc 5th International Congress International Association of Engineering Geology, Buenos Aires, 20-25 October 1986 V3, P1797-1805. Publ Rotterdam: A A Balkema, 1986 Engineering geology as a rational basis to characterise zones according to their likely behaviour under seismic excitation is discussed. The modifying effects of local geology, amplification, attenuation or prolongation of ground motion or volume effects of sediment filled valleys, and induced effects, liquefaction, slope failure and surface rupture, are examined. The mapping is applied to the city of Faro, Portugal.
Geophysical techniques 885191 Low frequency seismology and three-dimensional structureobservational aspects Masters, G; Ritzwoller, M In: Vlaar, N J et al (eels), Mathematical Geophysics: a Survey of Recent Developments in Seismology and _ Geodynamics PI-30. Publ Reidel: Dordrecht, 1988 The availability of a large quantity of long period digital seismic data has aided recent advances in the understanding of the large scale aspherical structure of the Earth. Low frequency digital data are briefly discussed, highlighting some observational problems encountered. This is followed by an overview of the theoretical background required to model long period data and an evaluation of some recently proposed 3-D models.
885192 Surface waves in weakly heterogeneous media Yomogida, K In: Vlaar, N J et al (eds), Mathematical Geophysics: a Survey of Recent Developments in Seismology and Geodynamics P53-75. Publ Reidel." Dordrecht, 1988 A review of the theory of surface wave propagation in media with weak lateral heterogeneities is presented. The formulations of surface waves share many common features with acoustic or elastic body waves in two-dimensional media, so direct application of theories such as the Gaussian beam method and the Maslov method are applicable to surface wave problems. Asymptotic ray theory, paraxial ray approximation, ray tracing on the sphere and inverse problems:Born approximation are all considered.
885193 Hybrid solution for wave propagation problems in inhomogeneous media van den Berg, A In: Vlaar, N J e t al (eds), Mathematical Geophysics: a Survey of Recent Developments in Seismology and Geodynamics P85-116. Publ Reidel: Dordrecht, 1988 A method to compute wave fields in inhomogeneous media, based on a hybrid formulation in terms of finite elements and a boundary integral representation. Numerical aspects of the method are discussed, and computational results for a simple model configuration are compared with analytical results. The method is applied in a seismic modelling experiment, where the effect of a low velocity sediment fill at the surface of a
halfspace on an incident teleseismic wave is modelled. The results clearly illustrate the strong amplification effect of the sediments on the surface displacements. Auth.
885194 Mathematical geophysics: A survey of recent developments in seismology and geodynamics Vlaar, N J; Nolet, G; Wortel, M J R; Cloetingh, S A P L (editors) Dordrecht: Reidel, 1988, 407P An up-to-date text covering modem methods for determining the structure of the Earth, and for the analysis and modelling of dynamic processes in the Earth's interior. Theoretical aspects are emphasised. There are 2 sections: (1) seismology and three dimensional structure of the Earth, including waves in a 3-D Earth and large-scale inversion; and (2) convection and lithospheric processes, including geomagnetism, mantle convection, postglacial rebound and therrnomechanical processes in the lithosphere.
885195 Geophysical logging applied to post tensioning anchor construction Raper, R W J; London-Jones, I A; Van Breda, P; Atkinson, P A Aust Geomech NI3, June 1987, P7-15 Remedial work at the Cataract Dam, Australia, requires holes to be drilled through the dam to the sandstone foundations, for the installation of post tensioned anchors. The drillholes were logged to determine foundation geology and hydrology, to assist design of the waterproofing and grouting operations. On the basis of verticality, 3 arm caliper, and dual focused electric (sonic-resistivity) logs, a cost effective restoration was possible.
885196 Fracture detection using P-wave and S-wave vertical seismic profiling at The Geysers Majer, E L; McEvilly, T V; Eastwood, F S; Myer, L R Geophysics V53, NI, Jan 1988, P76-84 Vertical seismic profiling (VSP) may be useful to detect dominant fractures, an important factor in reservoir engineering. The technique was used at The Geysers, which has a well known fracture geometry. The study showed anisotropy to Swaves caused an I1% velocity difference and an apparent splitting of SH-polarised and SV-polarised waves, which is consistent with known fracture geometry.
885197 Three-dimensional model results for an electrical hole-tosurface method: application to the interpretation of a field survey Le Masne, D; Poirmeur, C Geophysics V53, NI, Jan 1988, P85-103 The ELECENT electrical hole-to-surface method is designed to detect and locate inhomogeneities not intersected by the borehole. A quantitative assessment of theoretical responses of this array using a computer allows definition of those parameters most useful in interpretation of field surveys. Two surface measurements are made: electrical potential and horizontal electrical field. These measurements give rise to 3 other parameters, and the influence of various geometrical and electrical parameters on the 5 parameters appears to be important. A field survey at Beauvain prospect shows good agreement with theoretical results.
1988 Pergamon Press plc. Reproduction not permitted
885190 Engineering geological mapping for seismic microzonation Gomes Coelho, A Proc 5th International Congress International Association of Engineering Geology, Buenos Aires, 20-25 October 1986 V3, P1797-1805. Publ Rotterdam: A A Balkema, 1986 Engineering geology as a rational basis to characterise zones according to their likely behaviour under seismic excitation is discussed. The modifying effects of local geology, amplification, attenuation or prolongation of ground motion or volume effects of sediment filled valleys, and induced effects, liquefaction, slope failure and surface rupture, are examined. The mapping is applied to the city of Faro, Portugal.
Geophysical techniques 885191 Low frequency seismology and three-dimensional structureobservational aspects Masters, G; Ritzwoller, M In: Vlaar, N J et al (eels), Mathematical Geophysics: a Survey of Recent Developments in Seismology and _ Geodynamics PI-30. Publ Reidel: Dordrecht, 1988 The availability of a large quantity of long period digital seismic data has aided recent advances in the understanding of the large scale aspherical structure of the Earth. Low frequency digital data are briefly discussed, highlighting some observational problems encountered. This is followed by an overview of the theoretical background required to model long period data and an evaluation of some recently proposed 3-D models.
885192 Surface waves in weakly heterogeneous media Yomogida, K In: Vlaar, N J et al (eds), Mathematical Geophysics: a Survey of Recent Developments in Seismology and Geodynamics P53-75. Publ Reidel." Dordrecht, 1988 A review of the theory of surface wave propagation in media with weak lateral heterogeneities is presented. The formulations of surface waves share many common features with acoustic or elastic body waves in two-dimensional media, so direct application of theories such as the Gaussian beam method and the Maslov method are applicable to surface wave problems. Asymptotic ray theory, paraxial ray approximation, ray tracing on the sphere and inverse problems:Born approximation are all considered.
885193 Hybrid solution for wave propagation problems in inhomogeneous media van den Berg, A In: Vlaar, N J e t al (eds), Mathematical Geophysics: a Survey of Recent Developments in Seismology and Geodynamics P85-116. Publ Reidel: Dordrecht, 1988 A method to compute wave fields in inhomogeneous media, based on a hybrid formulation in terms of finite elements and a boundary integral representation. Numerical aspects of the method are discussed, and computational results for a simple model configuration are compared with analytical results. The method is applied in a seismic modelling experiment, where the effect of a low velocity sediment fill at the surface of a
halfspace on an incident teleseismic wave is modelled. The results clearly illustrate the strong amplification effect of the sediments on the surface displacements. Auth.
885194 Mathematical geophysics: A survey of recent developments in seismology and geodynamics Vlaar, N J; Nolet, G; Wortel, M J R; Cloetingh, S A P L (editors) Dordrecht: Reidel, 1988, 407P An up-to-date text covering modem methods for determining the structure of the Earth, and for the analysis and modelling of dynamic processes in the Earth's interior. Theoretical aspects are emphasised. There are 2 sections: (1) seismology and three dimensional structure of the Earth, including waves in a 3-D Earth and large-scale inversion; and (2) convection and lithospheric processes, including geomagnetism, mantle convection, postglacial rebound and therrnomechanical processes in the lithosphere.
885195 Geophysical logging applied to post tensioning anchor construction Raper, R W J; London-Jones, I A; Van Breda, P; Atkinson, P A Aust Geomech NI3, June 1987, P7-15 Remedial work at the Cataract Dam, Australia, requires holes to be drilled through the dam to the sandstone foundations, for the installation of post tensioned anchors. The drillholes were logged to determine foundation geology and hydrology, to assist design of the waterproofing and grouting operations. On the basis of verticality, 3 arm caliper, and dual focused electric (sonic-resistivity) logs, a cost effective restoration was possible.
885196 Fracture detection using P-wave and S-wave vertical seismic profiling at The Geysers Majer, E L; McEvilly, T V; Eastwood, F S; Myer, L R Geophysics V53, NI, Jan 1988, P76-84 Vertical seismic profiling (VSP) may be useful to detect dominant fractures, an important factor in reservoir engineering. The technique was used at The Geysers, which has a well known fracture geometry. The study showed anisotropy to Swaves caused an I1% velocity difference and an apparent splitting of SH-polarised and SV-polarised waves, which is consistent with known fracture geometry.
885197 Three-dimensional model results for an electrical hole-tosurface method: application to the interpretation of a field survey Le Masne, D; Poirmeur, C Geophysics V53, NI, Jan 1988, P85-103 The ELECENT electrical hole-to-surface method is designed to detect and locate inhomogeneities not intersected by the borehole. A quantitative assessment of theoretical responses of this array using a computer allows definition of those parameters most useful in interpretation of field surveys. Two surface measurements are made: electrical potential and horizontal electrical field. These measurements give rise to 3 other parameters, and the influence of various geometrical and electrical parameters on the 5 parameters appears to be important. A field survey at Beauvain prospect shows good agreement with theoretical results.
1988 Pergamon Press plc. Reproduction not permitted