A 4th order accurate P-SV wave staggered grid finite difference algorithm with variable grid size and VGR-stress imaging technique
In: Geofizika; ISSN 0352-3659 (Print); ISSN 1846-6346 (Online); Volume 27; Issue 1; (2010)
Online
Elektronische Ressource
The implementation of VGR-stress imaging technique, as a free surface boundary condition, in a (2, 4) staggered grid P-SV wave finite difference (FD) algorithm with a variable size of a grid cell is presented in this paper. VGR is acronym for 'vertical grid-size reduction'. The qualitative and quantitative results confirmed that the effective thickness (ETH) of the first soil layer become less by one-half of the vertical size of a grid cell than the assigned thickness (ATH), if stress imaging technique is used as a free surface boundary condition. The results of various numerical experiments revealed that the stress imaging technique causes significant numerical dispersion of Rayleigh waves and the VGR-stress imaging technique is efficient enough to avoid the same. So, superiority associated with the VGR-stress imaging technique over the well stress imaging technique is that it avoids both the significant numerical dispersion of Rayleigh waves in homogeneous medium and the soil thickness discrepancy. The maximum grid spacing ratio (ratio of largest to smallest size of a grid cell) up to 6.0 did not affect the accuracy of FD algorithm with a variable size of a grid cell. In case of a variable size of a grid cell, the required computational memory and time for a particular basin-edge model was 6.43 and 16.62 times lesser than that required in case of uniform grid.
Prikazana je primjena VGR-metode dijagnostike napetosti (engl. VGR-stress imaging technique), kao slobodnog rubnog uvjeta na površini, u (2,4) P-SV valnom algoritmu konačnih razlika (engl. finite difference, FD) na razmaknutoj mreži s varijabilnom veličinom mrežne ćelije. VGR je akronim za smanjenje vertikalne veličine mreže (engl. vertical grid-size reduction). Kvalitativni i kvantitativni rezultati potvrdili su da efektivna debljina (engl. effective thickness, ETH) prvog sloja tla postaje za polovinu vertikalnog koraka mreže manja od pridijeljene debljine (engl. assigned thickness, ATH), ukoliko se metoda dijagnostike napetosti koristi kao slobodan rubni uvjet na površini. Rezultati različitih numeričkih eksperimenata otkrili su da uobičajeno korištena metoda dijagnostike naprezanja dovodi do značajne numeričke disperzije Rayleighevih valova, dok je VGR-metoda dovoljno učinkovita da to izbjegne. Nadmoć VGR-metode nad dobro poznatom metodom dijagnostike napetosti se stoga očituje u izbjegavanju značajne numeričke disperzije Rayleighevih valova u homogenom sredstvu, kao i manjem odstupanju u debljini sloja tla. Maksimalni omjer koraka mreže (tj. omjer najveće prema najmanjoj veličini mrežne ćelije) do 6.0 nije utjecao na točnost FD algoritma s varijabilnom veličinom mrežne ćelije. U slučaju varijabilne mreže, računalna memorija i vrijeme računanja potrebni za određeni model ruba bazena bili su 6.43, odnosno 16.62 puta manji nego u slučaju jednolike mreže.
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A 4th order accurate P-SV wave staggered grid finite difference algorithm with variable grid size and VGR-stress imaging technique
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Quelle: | Geofizika; ISSN 0352-3659 (Print); ISSN 1846-6346 (Online); Volume 27; Issue 1; (2010) |
Veröffentlichung: | 2010 |
Medientyp: | Elektronische Ressource |
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