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Testing four elasctic finite-difference schemes for behavior at discontinuities
335A considered to include lithology of first bedrock layer beneath the lagoon, thickness of surficial layers, seepage rate, and proximity to existing sinkholes.
Earthquake mechanisms and effects See also: 936196 936016 Wave diffraction, amplification and differential motion near strong lateral discontinuities Moczo, P; Bard, P Y Bull Seismol Soc Am V83, N1, Feb 1993, P85-106
Earthquake damage has been observed to be concentrated along strong lateral discontinuities, where materials with different rigidities are in contact. Numerical investigation of this phenomenon for a semi-infinite soft planar layer embedded in stiffer bedrock is presented. A finite difference scheme including anelastic attenuation is used. Both translational and twisting motion at the discontinuity are found as a result of seismic wave propagation. 936017 Testing four elastic finite-difference schemes for behavior at discontinuities Zahradnik, J; Moczo, P; Hron, F Bull Seismol Soc Am V83, N1, Feb 1993, P107-129
Four finite difference schemes (3 second order, 1 fourth order) have been tested theoretically and numerically for their behaviour at elastic discontinuities. One is extended with new formulae for a flat free surface. Two are consistent with the stress-continuity condition for P-SV waves of discontinuities coinciding with horizontal or vertical grid lines: none is consistent at diagonal discontinuities. Numerical results from all the schemes are similar and compare well with semianalytic solutions for 3 of the models. Although these schemes are not free from accuracy problems at elastic discontinuities, they are still useful for generation of synthetic seismograms. 936018 Characteristics of nonlinear soil response Yu, G; Anderson, J G; Siddharthan, R Bull Seismol Soc Am V83, N1, Feb 1993, P218-244
A numerical code is presented for calculating the time domain response of a nonlinear soil to base excitation and is used to examine strong motion seismograms recorded in the soil. The model can reproduce several features which are usually taken to be indicative of nonlinearity, decreased statistical uncertainty in prediction of peak acceleration, decreased spectral ratios of surface-to-input motion near the dominant frequency, and increased effective period of surface motion. 936019 Indirect boundary element method applied to simulate the seismic response of alluvial valleys for incident P, S and Rayleigh waves Sanchez-Sesma, F J; Ramos-Martinez, J; Campillo, M Earthq Engng Struet Dynam II22, N4, April 1993, P279-295
Local topographic and geological conditions may promote amplification of ground motion and damage. A single-layer boundary representation of elastic wavefields is presented and used to compute the response of various models of alluvial deposits for incident elastic waves in a half space. Comparisons are made with exact and numerical solutions. The response of a semi-elliptical valley to incident Rayleigh waves
is studied in the frequency and time domains. Significant influence of locally generated surface waves on seismic response is Seen.
936020 Earthquake probability in engineering - Part 1: The use and misuse of expert opinion Krinitzky, E L Engng Geol V33, N4, April 1993, P257-288
The Third Richard H Jahns Distinguished Lecture in Engineering Geology. The Lawrence Livermore National Laboratory and EPRI in the USA have developed statistical procedures which allow merging of multiple expert opinions to give probabilistic seismic hazard evaluations. Examination of results indicates that such subjective group estimations are intrinsically defective and should not form a basis for design applications in engineering. 936021 Environmental aspects of reservoir induced seismicity Vladut, T Int Water Power Dam Constr V45, N5, May 1993, P29-33
Over 100 cases of reservoir induced seismicity have been reported. Recent study of some 60 RIS events is discussed. The empirical rules for risk identification based on water depth and reservoir area and volume, the past non-dimensional methods to estimate RIS risks, and existing procedures to control or design rates of impoundment are confirmed. 936022 Interaction of the San Andreas fault creeping segment with adjacent great rupture zones and earthquake recurrence at Parkfield Ben-Zion, Y; Rice, J R; Dmowska, R J Geophys Res V98, NB2, Feb 1993, P2135-2144
The San Andreas Fault rupture zones of the great earthquakes of 1857 and 1906 are presumed to slip only in great events, at least at depths less than 10-12km. Three dimensional finite element analysis of the region is presented, with the fault locked against creep except in great earthquakes at the zones corresponding to the 1857 and 1906 events, but freely creeping between and below the locked zones. Time dependency of the great earthquakes is examined and it is found that the hypothesis of characteristic period events at Parkfield may not give the best estimate. 936023 Spectra of seismic radiation from a tensile crack Walter, W R; Brune, J N 1 Geophys Res V98, NB3, March 1993, P4449-4459
A model is presented for the average far-field P and S wave amplitude spectra from a circular crack failing in tension. No details of the rupture process are specified, but spectral amplitude is determined by applying physically realistic constraints to an idealized spectral shape for each wave type. P and S wave models for tensile and shear cracks are compared, the tensile crack having the lower average S/P spectral amplitude. Applications to identification of tensile contributions to earthquake rupture are considered. 936024 Dynamics of fault interaction: parallel strike-slip faults Harris, R A; Day, S M J Geophys Res V98, NB3, March 1993, P4461-4472
Two dimensional finite difference modelling of the effect of fault steps on dynamic rupture is presented. Results suggest strike slip earthquakes are able to jump fault steps of width up
© 1993 Pergamon Press Ltd. Reproduction not permitted
Earthquake mechanisms and effects See also: 936196 936016 Wave diffraction, amplification and differential motion near strong lateral discontinuities Moczo, P; Bard, P Y Bull Seismol Soc Am V83, N1, Feb 1993, P85-106
Earthquake damage has been observed to be concentrated along strong lateral discontinuities, where materials with different rigidities are in contact. Numerical investigation of this phenomenon for a semi-infinite soft planar layer embedded in stiffer bedrock is presented. A finite difference scheme including anelastic attenuation is used. Both translational and twisting motion at the discontinuity are found as a result of seismic wave propagation. 936017 Testing four elastic finite-difference schemes for behavior at discontinuities Zahradnik, J; Moczo, P; Hron, F Bull Seismol Soc Am V83, N1, Feb 1993, P107-129
Four finite difference schemes (3 second order, 1 fourth order) have been tested theoretically and numerically for their behaviour at elastic discontinuities. One is extended with new formulae for a flat free surface. Two are consistent with the stress-continuity condition for P-SV waves of discontinuities coinciding with horizontal or vertical grid lines: none is consistent at diagonal discontinuities. Numerical results from all the schemes are similar and compare well with semianalytic solutions for 3 of the models. Although these schemes are not free from accuracy problems at elastic discontinuities, they are still useful for generation of synthetic seismograms. 936018 Characteristics of nonlinear soil response Yu, G; Anderson, J G; Siddharthan, R Bull Seismol Soc Am V83, N1, Feb 1993, P218-244
A numerical code is presented for calculating the time domain response of a nonlinear soil to base excitation and is used to examine strong motion seismograms recorded in the soil. The model can reproduce several features which are usually taken to be indicative of nonlinearity, decreased statistical uncertainty in prediction of peak acceleration, decreased spectral ratios of surface-to-input motion near the dominant frequency, and increased effective period of surface motion. 936019 Indirect boundary element method applied to simulate the seismic response of alluvial valleys for incident P, S and Rayleigh waves Sanchez-Sesma, F J; Ramos-Martinez, J; Campillo, M Earthq Engng Struet Dynam II22, N4, April 1993, P279-295
Local topographic and geological conditions may promote amplification of ground motion and damage. A single-layer boundary representation of elastic wavefields is presented and used to compute the response of various models of alluvial deposits for incident elastic waves in a half space. Comparisons are made with exact and numerical solutions. The response of a semi-elliptical valley to incident Rayleigh waves
is studied in the frequency and time domains. Significant influence of locally generated surface waves on seismic response is Seen.
936020 Earthquake probability in engineering - Part 1: The use and misuse of expert opinion Krinitzky, E L Engng Geol V33, N4, April 1993, P257-288
The Third Richard H Jahns Distinguished Lecture in Engineering Geology. The Lawrence Livermore National Laboratory and EPRI in the USA have developed statistical procedures which allow merging of multiple expert opinions to give probabilistic seismic hazard evaluations. Examination of results indicates that such subjective group estimations are intrinsically defective and should not form a basis for design applications in engineering. 936021 Environmental aspects of reservoir induced seismicity Vladut, T Int Water Power Dam Constr V45, N5, May 1993, P29-33
Over 100 cases of reservoir induced seismicity have been reported. Recent study of some 60 RIS events is discussed. The empirical rules for risk identification based on water depth and reservoir area and volume, the past non-dimensional methods to estimate RIS risks, and existing procedures to control or design rates of impoundment are confirmed. 936022 Interaction of the San Andreas fault creeping segment with adjacent great rupture zones and earthquake recurrence at Parkfield Ben-Zion, Y; Rice, J R; Dmowska, R J Geophys Res V98, NB2, Feb 1993, P2135-2144
The San Andreas Fault rupture zones of the great earthquakes of 1857 and 1906 are presumed to slip only in great events, at least at depths less than 10-12km. Three dimensional finite element analysis of the region is presented, with the fault locked against creep except in great earthquakes at the zones corresponding to the 1857 and 1906 events, but freely creeping between and below the locked zones. Time dependency of the great earthquakes is examined and it is found that the hypothesis of characteristic period events at Parkfield may not give the best estimate. 936023 Spectra of seismic radiation from a tensile crack Walter, W R; Brune, J N 1 Geophys Res V98, NB3, March 1993, P4449-4459
A model is presented for the average far-field P and S wave amplitude spectra from a circular crack failing in tension. No details of the rupture process are specified, but spectral amplitude is determined by applying physically realistic constraints to an idealized spectral shape for each wave type. P and S wave models for tensile and shear cracks are compared, the tensile crack having the lower average S/P spectral amplitude. Applications to identification of tensile contributions to earthquake rupture are considered. 936024 Dynamics of fault interaction: parallel strike-slip faults Harris, R A; Day, S M J Geophys Res V98, NB3, March 1993, P4461-4472
Two dimensional finite difference modelling of the effect of fault steps on dynamic rupture is presented. Results suggest strike slip earthquakes are able to jump fault steps of width up
© 1993 Pergamon Press Ltd. Reproduction not permitted