Cascade earthquake and tsunami hazard assessment: A deterministic perspective for engineering purposes

Abstract

Preventive management strategies are evolving towards multi-hazard risk estimates. Commonly, the multi-hazard characterization is pursued following a probabilistic approach. However, scenario-based evaluations can provide complementary key insights of relevance to design critical facilities.In this paper, an alternative deterministic analysis was explored to characterize the cascade seismic and tsunami actions of a 1755-alike Great Lisbon Earthquake and Tsunami event oriented to the container terminal of Sines deep-water seaport, Portugal, which is in expansion to increase the current 2.3 million TEU capacity to 7.1 million TEU.The analysis accounts source, propagation and site effects uncertainties influencing the multi-hazard estimates for different structural configurations representing the different stages of the extension plans for the infrastructure.The target-hazard assessment assumes ground motion acceleration and tsunami hydrostatic and hydrodynamic quantities as explanatory variables, respectively obtained from ground motion prediction equations and non-linear Shallow-Water equations. The intensity measures inherent to each of the inextricable candidate sources, Scandidate, were characterized over 864 seismic and 144 tsunami simulations and then compared to key-thresholds to identify the scenarios with damaging potential, Seligible. The quantities of each Seligible were assessed varying the earthquake and tsunami intensity measures as leading measures to define a set of combined worst-case scenarios for the infrastructure, Sworst. The cascading loading patterns for structural design purposes are then derived following the European and North American code provisions for earthquake and tsunami actions, respectively.The prediction of the cascading loading pattern at the terminal container of the Sines port quantifies PGA around 0.37 g for a seismic displacement-controlled behavior and peaks of hydrostatic and hydrodynamic components values around 1000 kNm−1 for tsunami force-controlled behavior during both the inflow and outflow cycles. A brief correlation between indicative action values and structural resistance of the current constructive solution raises awareness for the high probability of structural collapse of the pile-supported wharf due to an extreme 1755-alike Great Lisbon Earthquake and Tsunami threat, which would disrupt the port's operations and compromise its role as lifeline structure in case of emergency.