This project is thus expected to produce carefully validated computer codes for ground motion modelling, with due consideration to source, path and site effects, which should in turn result in an improved assessment of seismic actions for civil engineering structures.
Recent destructive earthquakes have repeatedly shown that one of important cause of the occurrence of disaster (even in developed countries) was the underestimation of ground motion, or of certain of their characteristics. The research objective of this proposal is the improvement of the ground motion estimates through a careful and validated integration of already existing numerical modelling techniques, that take proper account of all the physical phenomena affecting the amplitude and spectral characteristics of seismic waves, without overemphasizing or minimizing any of them.
One important goal of the present proposal is thus to merge the various numerical techniques developed separately in each of the 4 involved teams, and whose original aim was to investigate one particular effect (various source effects or crustal effects, or one category of site effects): these techniques include ray methods, finite-difference (FD) techniques, discrete wave-number method (DWN), matrix (1D) methods, empirical Green's function methods (EGF) and non-linear methods (NL). However, in order to have physical constraints on the way to merge these techniques, and on the respective importance of the effects they separately model, this integration will be extensively tested against high quality, well constrained instrumental data.
The research activities will start with a careful selection of some data sets from the weak and moderate events recorded by the Volvi lake arrays, and the translation of all the seismological, geophysical, geological and geotechnical information into appropriate models for numerical processing. The respective influence and importance of source and path effects will be investigated through the successive use of point source ray methods, point source DWN methods with instantaneous or finite source- function, extended source with deterministic or stochastic rupture process, and the comparison of their results with the actual records obtained at site-effect-free locations (unweathered rock sites). Investigations on site effects will focus on the assessment of the importance of the diffraction effects of local heterogeneities (comparison between 1D, 2D and 3D estimates, and with records obtained for weak events), and on the assessment of the motion levels beyond which non-linear effects become important. The integrated modelling of selected weak and moderate events (as well as real strong events in case of their occurrence in the life of the project) should then result in the identification of the deterministically predictable and non-predictable ground motion features, through a careful check of how the available data explain (or do not explain) the ground motion.
Funding SchemeCSC - Cost-sharing contracts
180 00 Praha 8
842 28 Bratislava