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Spatial variation of ground motion due to lateral heterogeneity
AbstractTo examine the effect of propagation on coherency of ground motion, a study of data from seismic arrays on hard rock has been carried out. In addition coherency results using finite difference seismograms for a layer over a half-space with heterogeneities are presented. The hard rock sites are three arrays in Fennoscandia; maximum array spacings are 1500–3000 m. The data analysed are S-waves from quarry blasts at ranges of 240–350 km. Analyses at 2, 4 and 6 Hz show high coherency as a function of separation compared to sites with alluvium or soil layers. Tentatively, we conclude that the decay of coherency with separation at each site follows a single relation for all frequencies if the separation is scaled by the wavelength. The two-dimensional finite difference results indicate that even with no heterogeneities the mixing of reflected P and S phases in a surface layer can substantially reduce the coherency for the vertical component if the source is below the layer. For the horizontal (radial) component, the effect of velocity heterogeneity is to reduce the coherency while layering and irregular layer interfaces have less effect, at least for sources below the layer.
Spatial variation of ground motion due to lateral heterogeneity
AbstractTo examine the effect of propagation on coherency of ground motion, a study of data from seismic arrays on hard rock has been carried out. In addition coherency results using finite difference seismograms for a layer over a half-space with heterogeneities are presented. The hard rock sites are three arrays in Fennoscandia; maximum array spacings are 1500–3000 m. The data analysed are S-waves from quarry blasts at ranges of 240–350 km. Analyses at 2, 4 and 6 Hz show high coherency as a function of separation compared to sites with alluvium or soil layers. Tentatively, we conclude that the decay of coherency with separation at each site follows a single relation for all frequencies if the separation is scaled by the wavelength. The two-dimensional finite difference results indicate that even with no heterogeneities the mixing of reflected P and S phases in a surface layer can substantially reduce the coherency for the vertical component if the source is below the layer. For the horizontal (radial) component, the effect of velocity heterogeneity is to reduce the coherency while layering and irregular layer interfaces have less effect, at least for sources below the layer.
Spatial variation of ground motion due to lateral heterogeneity
Toksöz, M.Nafi (author) / Dainty, Anton M. (author) / Charrette, E.E. III (author)
Structural Safety ; 10 ; 53-77
1991-01-01
25 pages
Article (Journal)
Electronic Resource
English
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