NON LINEAR SEISMOLOGY A REALITY . THE IMPLICATIONS IN EARTHQUAKE ENGINEERING NGINEERING

Most cities and villages are located on alluvial deposits/sediments, on Quaternary layers in river valleys. The seismological detection of the nonlinear site effects requires a simultaneous understanding of the effects of earthquake source, propagation path and local geological site conditions. To see the actual influence of nonlinearity of the whole system (seismic source-path propagation-local geological structure) the authors used to study the response spectra because they are the last in this chain and are taken into account in seismic design of structures. The evidence for nonlinearity for Bucharest and extra-Carpathian area is given by a systematic relative decrease in the variability of peak ground acceleration with the increasing earthquake magnitude The spectral amplification factors for last three strong and deep Vrancea earthquakes are larger than the values given by Regulatory Guide 1.60 of the U. S. Atomic Energy Commission and IAEA Vienna-through Safety Series No.5-SG-S1.