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Multiple failure surfaces over dip-slip faults
173A of about 1450m. The azimuths of the breakouts are consistent with depths and indicate a stress direction which is in good agreement with the interpretation of fault plane solutions of nearby earthquakes. 845087 Structural interpretation of the St. Eloy coal basin from mechanical tests and tectonic models (In French) Bergues, J; Grolier, J; Soula, J C; Travert, P Proc 5th Congress of the International Society for Rock Mechanics, Melbourne, 10-15 April 1983 V2, PE1-E5. Pub[ Rotterdam: A. A. Balkema, 1983 The structural geology of the St. Eloy coal basin suggests coal creep towards anticlinal hinges. The rheological behaviour of the coal is established according to rock mechanical properties and the structure of the basin is tentatively explained by analagous tectonic models. 845088 Geology and rock stresses in deep boreholes at Forsmark in Sweden Martna, J; Hiltscher, R; Ingevald, K Proc 5th Congress of the International Society for Rock Mechanics, Melbourne, 10-15 April 1983 V2, PFl l l-Fl l6. Publ Rotterdam: A. A. Balkema, 1983 Rock stress measurements made in two research boreholes, 503 and 250m deep respectively, are given together with a description of the geology and the tectonic features of the area. The boreholes are located in a Precambrian gneiss granite with dykes of dolerite and pegmatite. The principal stresses are almost horizontal and vertical. Down to 320m the horizontal stresses remain more or less unchanged with average values of about 15-20MPa. The vertical stress increases on the whole with the weight of the overburden. At a depth of 320m a fractured zone of rock is penetrated. Below this zone the horizontal stresses increase abruptly to 65MPa and possibly over this value. The results demonstrate that the initial rock stresses may change abruptly and considerably even in a seemingly homogeneous rock and need not necessarily follow any particular law. Therefore comprehensive local measurements are necessary in every case for the knowledge of the stresses in a sizeable rock mass. Auth. Tectonic processes 845089 Activation of Gulf Coast faults by depressuring of aquifers and an engineering approach to siting structures along their traces O'Neill, M W; Van Siclen, D C Bull Assoc Engng Geol 1/21, N1, Feb 1984, P73-87 A simple mechanism is described by which geologic faults in near-surface sediments along the Texas Gulf Coast may be reactivated by uniform lowering of the piezometric surface by geofluid extraction. This mechanism requires a pre-existing fault and is independent of local differential compaction, which, however, is not excluded from contributing to fault activation. Based on this mechanism, an elementary procedure for estimating the drawdown necessary to activate pre-existing faults is described. Results of a finite element analysis to predict the pattern of surface distortion in the vicinity of a hypothetical active fault in the Houston, Texas area are also presented and compared with profiles measured along streets. Finally, an objective procedure is described for determining how close to the trace of an active or potentially active fault structures can be placed without undergoing excessive distress. Auth.
845090 Relationship between strain rates, crustal thickening, palaeomagnetism, finite strain and fault movements within a deforming zone McKenzie, D; Jackson, J Earth Planet Sci Lett V65, N1, Oct 1983, P182-202 A deformation gradient tensor is derived, which determines the amount of crustal thickening and is related to the finite strain tensor. Palaeomagnetic measurements are generally made on rigid undeformed blocks, so there is no simple relationship between such rotations and the finite strain. Displacements along faults separating these rigid blocks are controlled by velocity gradients. Analytical expressions relating these quantities are obtained. 845091 Numerical modelling of space and time variations of seismic activity before major earthquakes Mikumo, T; Miyatake, T Geopbys J R Astr Soc V74, N2, Aug 1983, P559-583 Seismic activity before earthquakes is modelled by quasi-static and dynamic rupture processes on three-dimensional heterogeneous faults with various types of non-uniform strength distributions. It is suggested that certain patterns of seismic activity can predict the nature of the main shock. 49 refs. 845092 Nucleation and growth of strike slip faults in granite Segall, P; Pollard, D D J Geophys Res 1/88, NBI, 10 Jan 1983, P555-568 Fractures within the granodiorite of the central Sierra Nevada, California, USA, were studied to elucidate the mechanics of faulting in crystalline rocks, with emphasis on the nucleation of new fault surfaces and their subsequent propagation. It is concluded that, as deformation progressed, faulting evolved from relatively short, closely spaced faults to longer, more widely spaced fault zones. 845O93 Influence zones in alluvium over dip-sfip faults Cole, D A; Lade, P V J Geotech Engng Div ASCE Vl10, NGT5, May 1984, P599615 Tests were performed on dense and loose sand in a glass-walled fault test box to investigate the shapes and locations of failure surfaces that may occur in alluvium overlying active dip-slip faults. The experimental procedure is reviewed and the results of the tests with reverse and with normal movements along the bedrock faults are presented. Based on the experimental results, a simple model is developed to predict the shapes and locations of failure surfaces in the soil. These are determined as a function of the depth of the soil, the angle of dilation for the soil, and the dip angle of the fault. The conditions for development of a graben structure, as observed during normal movement on the bedrock fault, are also determined. 845O94 Multiple failure surfaces over dii~llp faults Lade, P V; Cole, D A; Cummings, D J Geotecb Engng Div ASCE V110, NGTS, May 1984, P616627 The shapes and locations of failure surfaces in alluvium overlying active dip-slip faults are studied on the basis of experiments performed in a fault test box. A simple model for predicting primary and secondary failure surfaces in the alluvium caused by unidirectional movement on the bedrock fault is reviewed. This model is employed to evaluate additional failure surfaces produced by fault movement in the opposite direction and subsequent to the initial movement. The shapes
174A and locations of these latter failure surfaces are almost unaffected by the presence of failure surfaces caused by the initial fault movement. Ground surface expressions in alluvium associated with movements on dip-slip faults are summarized. Three field cases are reviewed and related to the experimental observations and the proposed simple model. This model is used to predict shapes and locations of failure surfaces in alluvium overlying dip-slip faults. Model predictions compare favourably with observations from the field. Auth. 845O95 Tectonic stress field in East Eurasia Eguchi, T Phys Earth Planet Inter V33, N4, Dec 1983, P318-327 845O96 Fault mechanism in the Toledo shear zone in Spain Hernandez-Enrile, J L Proc 5th Congress of the International Society for Rock Mechanics, Melbourne, 10-15 April 1983 V2, PF75-F78. Publ Rotterdam: A. A. Balkema, 1983 The microstructural development of the mylonite present in the Toledo shear zone has been examined in order to establish a macroscopic fracture mechanism. Microstructural development has occurred through dynamic recovery and dynamic recrystallization of the grains of the minerals present. The Toledo shear zone has developed under steady strain rates of aseismic shear. 845097 Measurements of tectonic stresses, strain rates related to active faults and observed earthquakes around large caverns Kanagawa, T; Komada, H; Hayashi, M Proc 5th Congress of the International Society for Rock Mechanics, Melbourne, 10-15 April 1983 V2, PF85-F88. Publ Rotterdam: A. A. Balkema, 1983 On the basis of approximately 20 experiments of tectonic stress measurements in large underground excavations and active faults the suitability of employing the acoustic emission method and a miniaturization of the overcoring method, as well as the effects of tectonics, topography and faults, are examined. Moreover, the connection between the geodetically ascertained shear strain rate in Japan and the range of historically observed earthquakes over the past 1200 years in the surroundings of underground power stations is discussed. Auth. 845098 Mechanisms of the deformation of the earth's crust - induced structures and anisotropy (In French) Deramond, J; Sirieys, P; Soula, J C Proc 5th Congress of the International Society for Rock Mechanics, Melbourne, 10-15 April 1983 V2, PF89.F93. Publ Rotterdam: A. A. Balkema, 1983 The deformation of the earth's crust appears as continuous (viscous or plastic flow) or discontinuous fracturing. Its mechanisms have been investigated with emphasis on the role of the structure of the deformed medium (strain induced or preexisting structure) which can be active or passive. Laboratory experiments on rock samples and analogical models are interpreted and applied to natural examples from the Pyrenees and the southern French Massif Central, relating to the opening of sedimentary basins and the sliding-spreading of nappes. Auth.
845O99 Rock mechanics and mathematical models applied to geology (In French) Quiblier, J A; Ngokwey, K Proc 5th Congress of the International Society for Rock Mechanics, Melbourne, 10-15 April 1983 V2, PF191-F194. Publ Rotterdam: A. A. Balkema, 1983 A large-deformation viscoelastic mathematical model applied to the overthrusting of two plates of the earth's crust clearly illustrates the deformation of the sedimentary cover and can be used to analyse various parameters. An elastic model applied to a fault can be used to determine the thrust that caused the fault to be propagated. Auth, Environmental effects, weathering and soil formation
See: 845348 Earthquake mechanisms and effects
See also: 845048, 845075 845100 Determination of seismic reference motion for nuclear sites in France Levret, A; Mohammadioun, B Engng Geol V20, N1-2, March 1984, P25-38 The Nuclear Safety Department in France has developed a method for site-specific hazard assessment, entailing the definition of specific reference motions. Seismotectonic criteria are used to define a site's reference earthquake, then corresponding ground motions are obtained by: (1) a thorough analysis of macroseismic data to define the characteristics of reference events; (2) calculation of ground motion from a statistical study of strong-motion records collected in a data bank, based on correlations between response spectra, magnitudes, focal distances and macroseismic intensities, corresponding to the records. A valid approach has recently been sought for taking nearby, lowmagnitude earthquakes into account, due to the high ground accelerations with which they are associated. 845101 Relations between ground motions and earthquake magnitude, focal distance and epicentrni intensity Schenk, V Engng Geol II20, 311-2, March 1984, P143-151 845102 On some problems related to soil failures and intensity evaluations. Short communication Gurpinar, A Engng Geol }'20, N1-2, March 1984, P181-185 The use of intensity values to describe seismic effects expected at a given site has become of significant engineering design interest. One problem area is the damage caused on soils of different quality. It is then important to separate the damage due to soil amplification from that of soil failure. Examples from recent earthquakes are given for illustration purposes. 845103 Seismic disturbance of 1976 March 20, East Kazakhstan: earthquake or explosions? Research note Pooley, C I; Douglas, A; Pearce, R G Geophys J R Astr Soc V74, N2, Aug 1983, P621-631
845090 Relationship between strain rates, crustal thickening, palaeomagnetism, finite strain and fault movements within a deforming zone McKenzie, D; Jackson, J Earth Planet Sci Lett V65, N1, Oct 1983, P182-202 A deformation gradient tensor is derived, which determines the amount of crustal thickening and is related to the finite strain tensor. Palaeomagnetic measurements are generally made on rigid undeformed blocks, so there is no simple relationship between such rotations and the finite strain. Displacements along faults separating these rigid blocks are controlled by velocity gradients. Analytical expressions relating these quantities are obtained. 845091 Numerical modelling of space and time variations of seismic activity before major earthquakes Mikumo, T; Miyatake, T Geopbys J R Astr Soc V74, N2, Aug 1983, P559-583 Seismic activity before earthquakes is modelled by quasi-static and dynamic rupture processes on three-dimensional heterogeneous faults with various types of non-uniform strength distributions. It is suggested that certain patterns of seismic activity can predict the nature of the main shock. 49 refs. 845092 Nucleation and growth of strike slip faults in granite Segall, P; Pollard, D D J Geophys Res 1/88, NBI, 10 Jan 1983, P555-568 Fractures within the granodiorite of the central Sierra Nevada, California, USA, were studied to elucidate the mechanics of faulting in crystalline rocks, with emphasis on the nucleation of new fault surfaces and their subsequent propagation. It is concluded that, as deformation progressed, faulting evolved from relatively short, closely spaced faults to longer, more widely spaced fault zones. 845O93 Influence zones in alluvium over dip-sfip faults Cole, D A; Lade, P V J Geotech Engng Div ASCE Vl10, NGT5, May 1984, P599615 Tests were performed on dense and loose sand in a glass-walled fault test box to investigate the shapes and locations of failure surfaces that may occur in alluvium overlying active dip-slip faults. The experimental procedure is reviewed and the results of the tests with reverse and with normal movements along the bedrock faults are presented. Based on the experimental results, a simple model is developed to predict the shapes and locations of failure surfaces in the soil. These are determined as a function of the depth of the soil, the angle of dilation for the soil, and the dip angle of the fault. The conditions for development of a graben structure, as observed during normal movement on the bedrock fault, are also determined. 845O94 Multiple failure surfaces over dii~llp faults Lade, P V; Cole, D A; Cummings, D J Geotecb Engng Div ASCE V110, NGTS, May 1984, P616627 The shapes and locations of failure surfaces in alluvium overlying active dip-slip faults are studied on the basis of experiments performed in a fault test box. A simple model for predicting primary and secondary failure surfaces in the alluvium caused by unidirectional movement on the bedrock fault is reviewed. This model is employed to evaluate additional failure surfaces produced by fault movement in the opposite direction and subsequent to the initial movement. The shapes
174A and locations of these latter failure surfaces are almost unaffected by the presence of failure surfaces caused by the initial fault movement. Ground surface expressions in alluvium associated with movements on dip-slip faults are summarized. Three field cases are reviewed and related to the experimental observations and the proposed simple model. This model is used to predict shapes and locations of failure surfaces in alluvium overlying dip-slip faults. Model predictions compare favourably with observations from the field. Auth. 845O95 Tectonic stress field in East Eurasia Eguchi, T Phys Earth Planet Inter V33, N4, Dec 1983, P318-327 845O96 Fault mechanism in the Toledo shear zone in Spain Hernandez-Enrile, J L Proc 5th Congress of the International Society for Rock Mechanics, Melbourne, 10-15 April 1983 V2, PF75-F78. Publ Rotterdam: A. A. Balkema, 1983 The microstructural development of the mylonite present in the Toledo shear zone has been examined in order to establish a macroscopic fracture mechanism. Microstructural development has occurred through dynamic recovery and dynamic recrystallization of the grains of the minerals present. The Toledo shear zone has developed under steady strain rates of aseismic shear. 845097 Measurements of tectonic stresses, strain rates related to active faults and observed earthquakes around large caverns Kanagawa, T; Komada, H; Hayashi, M Proc 5th Congress of the International Society for Rock Mechanics, Melbourne, 10-15 April 1983 V2, PF85-F88. Publ Rotterdam: A. A. Balkema, 1983 On the basis of approximately 20 experiments of tectonic stress measurements in large underground excavations and active faults the suitability of employing the acoustic emission method and a miniaturization of the overcoring method, as well as the effects of tectonics, topography and faults, are examined. Moreover, the connection between the geodetically ascertained shear strain rate in Japan and the range of historically observed earthquakes over the past 1200 years in the surroundings of underground power stations is discussed. Auth. 845098 Mechanisms of the deformation of the earth's crust - induced structures and anisotropy (In French) Deramond, J; Sirieys, P; Soula, J C Proc 5th Congress of the International Society for Rock Mechanics, Melbourne, 10-15 April 1983 V2, PF89.F93. Publ Rotterdam: A. A. Balkema, 1983 The deformation of the earth's crust appears as continuous (viscous or plastic flow) or discontinuous fracturing. Its mechanisms have been investigated with emphasis on the role of the structure of the deformed medium (strain induced or preexisting structure) which can be active or passive. Laboratory experiments on rock samples and analogical models are interpreted and applied to natural examples from the Pyrenees and the southern French Massif Central, relating to the opening of sedimentary basins and the sliding-spreading of nappes. Auth.
845O99 Rock mechanics and mathematical models applied to geology (In French) Quiblier, J A; Ngokwey, K Proc 5th Congress of the International Society for Rock Mechanics, Melbourne, 10-15 April 1983 V2, PF191-F194. Publ Rotterdam: A. A. Balkema, 1983 A large-deformation viscoelastic mathematical model applied to the overthrusting of two plates of the earth's crust clearly illustrates the deformation of the sedimentary cover and can be used to analyse various parameters. An elastic model applied to a fault can be used to determine the thrust that caused the fault to be propagated. Auth, Environmental effects, weathering and soil formation
See: 845348 Earthquake mechanisms and effects
See also: 845048, 845075 845100 Determination of seismic reference motion for nuclear sites in France Levret, A; Mohammadioun, B Engng Geol V20, N1-2, March 1984, P25-38 The Nuclear Safety Department in France has developed a method for site-specific hazard assessment, entailing the definition of specific reference motions. Seismotectonic criteria are used to define a site's reference earthquake, then corresponding ground motions are obtained by: (1) a thorough analysis of macroseismic data to define the characteristics of reference events; (2) calculation of ground motion from a statistical study of strong-motion records collected in a data bank, based on correlations between response spectra, magnitudes, focal distances and macroseismic intensities, corresponding to the records. A valid approach has recently been sought for taking nearby, lowmagnitude earthquakes into account, due to the high ground accelerations with which they are associated. 845101 Relations between ground motions and earthquake magnitude, focal distance and epicentrni intensity Schenk, V Engng Geol II20, 311-2, March 1984, P143-151 845102 On some problems related to soil failures and intensity evaluations. Short communication Gurpinar, A Engng Geol }'20, N1-2, March 1984, P181-185 The use of intensity values to describe seismic effects expected at a given site has become of significant engineering design interest. One problem area is the damage caused on soils of different quality. It is then important to separate the damage due to soil amplification from that of soil failure. Examples from recent earthquakes are given for illustration purposes. 845103 Seismic disturbance of 1976 March 20, East Kazakhstan: earthquake or explosions? Research note Pooley, C I; Douglas, A; Pearce, R G Geophys J R Astr Soc V74, N2, Aug 1983, P621-631