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Geology of seattle, Washington, United States of America
GEOMECHANICS ABSTRACTS
Geology
923004 Experiments on faulting in a two-layer cover sequence
Tectonic processes and structural geology
overlying a reactivated basement fault with oblique-slip Richard, P J Struct Geol V13, N4, 1991, P459-469
See also: 923041, 923220, 923399 923001
Geology of Seattle, Washington, United States of America Galster, R W; Laprade, W T Assoc Engng Geol V28, N3, Aug 1991, P235-302 A comprehensive description of the geology of the Seattle area is presented. The region is dominated by recent glacial deposits over older, less well characterised glacial deposits and nonglacial materials. Geological setting and geotechnical characteristics are described in detail. Local geotechnical practices in exploration and construction, available structural materials, geological constraints on developments, regional seismicity, and protection of the environment are discussed. Major projects in the area are described, including highways, bridges, canals, and tunnels. 923OO2
Geometric models of listric normal faults and roHover folds Dula, W F Bull Am Assoc Petrol Geol V75, NIO, Oct 1991, P1609-1625 Although geometric models are widely used to study fault geometry, it is not known which model best describes the relation between rollover and fault geometries. The ability of constant heave, constant displacement, constant bed length, slip line, and inclined shear constructions to do this has been examined. Results from clay model analogue tests are compared to seismic mapping data. 923OO3
Medslling, heat and fluid flow in sedimentary basins by the finite element method Wangen, M lint J Num Anal Meth Geomech VI5, NIO, Oct 1991, P705733 A 2D model of compaction of a water-saturated sedimentary basin is presented. Porosity is included as a function of effective stress, the anisotropic terms for permeability and thermal conductivity are functions of porosity. Water density is a function of water pressure and temperature, water viscosity a function of temperature alone. Three solution schemes for the nonlinear and coupled process are compared: Newmark's method applied to both equations simultaneously or sequentially,and the fixed point iteration method. Convection has litfie influence on the results. Water compressibility plays an important role for the excess pressure when it is greater than the rock compressibility.
Scale model tests to investigate the development of faults in a sedimentary cover over a reactivated basement fault with oblique slip are described. The effect of a ductile layer, such as the evaporite or clay sometimes found between sedimentary cover and basement, was investigated. The models used a Coulomb layer (sand) over a Newtonian ductile layer (silicone putty). The thickness of the silicone layer was varied. Both normal wrench and reverse wrench experiments were carried out. The effect of the ductile layer on distribution of the faulting in the overburden is discussed. 923005
Analysis of progressive deformation from an inscribed grid Mancktelow, N S J Struet Geoi VI3, N7, 1991, P859-864 Analysis of deformation of inscribed grids from scale model experiments is widely used to follow development of geological structures. Numerical methods to calculate values relative to finite deformation and instantaneous deformation rate from coordinates of digitised grid nodes are outlined. These values may be plotted directly as principal strain axes or their magnitudes can be contoured across the surface of a model. The practical advantages of representing deformation as an average homogeneous component on which is superimposed a heterogeneous component representing deviation from the standard state are examined. 923006
Characteristics of joint propagation across layer interfaces in sedimentary rocks Helgeson, D E; Aydin, A J Struct Geoi V13, Ng, 1991, P897-911 Physical continuity of joints from one layer to another has been examined in fractographic analysis of surface features of joint segments in an alternating siltstone and shale turbidite sequence in the Appalachian plateau. Joint propagation is seen to be controlled by changing lithology and interface properties. Physical continuity, which affects fracture permeability, is controlled by distribution of inhibiting layers and out of plane growth of fractures from one unit to another. 923007
Fractal analysis of fracturing in two African regions, from satellite imagery to ground scale Vignes-Adler, M; Le Page, A; Adler, P M Tectmmpkysies V196, NI /2, Sept 1991, P69-86 Two areas in Africa, one central (Cameroon, Congo, Central African Republic, Chad, Nigeria) and one western (Mauritania), were chosen for study. The fractal characteristics of the fracture fields were examined at various scales: satellite imagery, drainage networks of topographical maps, aerial
© 1992 Pergamon Press Ltd. Reproduction not permitted 139A
Geology
923004 Experiments on faulting in a two-layer cover sequence
Tectonic processes and structural geology
overlying a reactivated basement fault with oblique-slip Richard, P J Struct Geol V13, N4, 1991, P459-469
See also: 923041, 923220, 923399 923001
Geology of Seattle, Washington, United States of America Galster, R W; Laprade, W T Assoc Engng Geol V28, N3, Aug 1991, P235-302 A comprehensive description of the geology of the Seattle area is presented. The region is dominated by recent glacial deposits over older, less well characterised glacial deposits and nonglacial materials. Geological setting and geotechnical characteristics are described in detail. Local geotechnical practices in exploration and construction, available structural materials, geological constraints on developments, regional seismicity, and protection of the environment are discussed. Major projects in the area are described, including highways, bridges, canals, and tunnels. 923OO2
Geometric models of listric normal faults and roHover folds Dula, W F Bull Am Assoc Petrol Geol V75, NIO, Oct 1991, P1609-1625 Although geometric models are widely used to study fault geometry, it is not known which model best describes the relation between rollover and fault geometries. The ability of constant heave, constant displacement, constant bed length, slip line, and inclined shear constructions to do this has been examined. Results from clay model analogue tests are compared to seismic mapping data. 923OO3
Medslling, heat and fluid flow in sedimentary basins by the finite element method Wangen, M lint J Num Anal Meth Geomech VI5, NIO, Oct 1991, P705733 A 2D model of compaction of a water-saturated sedimentary basin is presented. Porosity is included as a function of effective stress, the anisotropic terms for permeability and thermal conductivity are functions of porosity. Water density is a function of water pressure and temperature, water viscosity a function of temperature alone. Three solution schemes for the nonlinear and coupled process are compared: Newmark's method applied to both equations simultaneously or sequentially,and the fixed point iteration method. Convection has litfie influence on the results. Water compressibility plays an important role for the excess pressure when it is greater than the rock compressibility.
Scale model tests to investigate the development of faults in a sedimentary cover over a reactivated basement fault with oblique slip are described. The effect of a ductile layer, such as the evaporite or clay sometimes found between sedimentary cover and basement, was investigated. The models used a Coulomb layer (sand) over a Newtonian ductile layer (silicone putty). The thickness of the silicone layer was varied. Both normal wrench and reverse wrench experiments were carried out. The effect of the ductile layer on distribution of the faulting in the overburden is discussed. 923005
Analysis of progressive deformation from an inscribed grid Mancktelow, N S J Struet Geoi VI3, N7, 1991, P859-864 Analysis of deformation of inscribed grids from scale model experiments is widely used to follow development of geological structures. Numerical methods to calculate values relative to finite deformation and instantaneous deformation rate from coordinates of digitised grid nodes are outlined. These values may be plotted directly as principal strain axes or their magnitudes can be contoured across the surface of a model. The practical advantages of representing deformation as an average homogeneous component on which is superimposed a heterogeneous component representing deviation from the standard state are examined. 923006
Characteristics of joint propagation across layer interfaces in sedimentary rocks Helgeson, D E; Aydin, A J Struct Geoi V13, Ng, 1991, P897-911 Physical continuity of joints from one layer to another has been examined in fractographic analysis of surface features of joint segments in an alternating siltstone and shale turbidite sequence in the Appalachian plateau. Joint propagation is seen to be controlled by changing lithology and interface properties. Physical continuity, which affects fracture permeability, is controlled by distribution of inhibiting layers and out of plane growth of fractures from one unit to another. 923007
Fractal analysis of fracturing in two African regions, from satellite imagery to ground scale Vignes-Adler, M; Le Page, A; Adler, P M Tectmmpkysies V196, NI /2, Sept 1991, P69-86 Two areas in Africa, one central (Cameroon, Congo, Central African Republic, Chad, Nigeria) and one western (Mauritania), were chosen for study. The fractal characteristics of the fracture fields were examined at various scales: satellite imagery, drainage networks of topographical maps, aerial
© 1992 Pergamon Press Ltd. Reproduction not permitted 139A