As a consequence of the change of paradigm in earthquake resistant design stronger design earthquakes now control the seismic design of important structures. These stronger earthquakes include the effects of near-field pulses, fault-normal motions, and near-field deep soil site motions. As a consequence, there is a strong need for the development of robust and reliable techniques for the assessment of long period earthquake ground motions especially for near field conditions. To provide an example to the assessment of long period ground motion a comparative study has been carried out for the Marmara Region, Turkey. The probabilistic earthquake hazard has been investigated using PEER-NGA (2007) and older generation attenuation relationships for PGA and SA (0.2s, 1s, 2s, 4s, 6s, 8s and 10s) corresponding to 50, 10 and 2 percent probabilities of exceedance in 50 years. PGA values were used to obtain the EuroCode whereas, SA(0.2s and 1s) were used to obtain the NEHRP (2003) based response spectra. SA (0.2s, 1s, 2s, 4s, 6s, 8s and 10s) values were used to plot the equi-hazard spectrum. Furthermore associated hazard deaggregation has been conducted for several selected sites to obtain rational estimates of the deterministic long period spectral accelerations and the deterministic spectral shapes. Comparison of the findings indicate significant variation of long period spectral accelerations. The accuracy of seismic design spectra given in current codes is not sufficient at these periods. There is also a need to develop guidelines for the selection of design basis ground motion for long period or highly nonlinear (softening) structure.
AGU Fall Meeting Abstracts
- Pub Date:
- December 2007
- 7212 Earthquake ground motions and engineering seismology