Nonlinear Seismology - The Seismology of the XXI Century
Abstract
Nonlinear effects in ground motion during large earthquakes have been a long controversial issue between seismologists and geotechnical engineers. Laboratory tests made by using resonant columns consistently show the reduction in shear modulus (G) and increase in damping ratio (D) with increasing shear strain ( ), i.e., G = G( ), respectively, D = D( ). Therefore nonlinear viscoelastic constitutive laws are required. 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. The difficulty for seismologists in assessing the nonlinear site effects is due to the fact that these are overshadowed by the overall patterns of shock generation and propagation. In order to bring evidence for nonlinear effects we have introduced the spectral amplification factor (SAF) as the ratio between the maximum values of the spectral absolute acceleration (Sa), relative velocity (Sv), and relative displacement (Sd) to the corresponding peak values obtained from the processed strong motion records. The main evidence of nonlinearity observed for the thick Romanian Plain Quaternary sediments is a systematic decrease in the variability of peak ground acceleration for increasing earthquake magnitudes.
- Publication:
-
Lecture Notes in Earth Sciences, Berlin Springer Verlag
- Pub Date:
- 2005
- Bibcode:
- 2005LNES..105...47M