Abstract:
In the framework of the ongoing European project “LESSLOSS – Risk Mitigation for Earthquakes and Landslides”, finite-fault seismological models are proposed to compute the earthquake scenarios for three urban areas – Istanbul (Turkey), Lisbon (Portugal) and Thessaloniki (Greece). For each case study, ground motion scenarios are developed for the most probable two events with different return periods, locations and magnitudes derived from historical and geological data. In this study, we simulate the accelerometric time series and response spectra for high frequency ground motion in the city of Lisbon and surrounding counties (Metropolitan Area of Lisbon), using two possible earthquake models: the inland source area of Lower Tagus Valley, M 5.7 (4.7) and a hypothesis of the offshore source area of the 1755 Lisbon, M 7.6. The stochastic and a new hybrid stochastic-deterministic approach, DSM are used in order to evaluate the ground shaking and to characterize its spatial variability. Results are presented in terms of Response Acceleration Spectra (PSA), Peak Ground Acceleration (PGA) and Peak Ground Velocity (PGV) respect to rock site. Then the site effects are evaluated by means of an equivalent stochastic non-linear one-dimensional ground response analysis of stratified soil profile units properly designed. A sensitive study is performed using different input parameters and different approaches in order to give the basic information to evaluate the range of uncertainty in seismic scenarios.
