Simona Esposito

Post-earthquake assessment and management for infrastructure systems: learning from the Canterbury (New Zealand) and L’Aquila (Italy) earthquakes

Both the April 6, 2009 L’Aquila (Italy) earthquake, and the 2010–2011 Canterbury (New Zealand) earthquake sequence provided unprecedented opportunity to enhance the understanding on earthquake performance of infrastructure systems, and to analyse still-opened issues affecting the post-earthquake assessment and management of infrastructure. This paper provides a succinct and holistic overview on the physical and functional performances of the gas, water, waste water, road and electric networks (this one to a limited extent for the L’Aquila case-study), following the moment magnitude (Mw) 6.3 L’Aquila earthquake, and two main events of the Canterbury earthquake sequence, namely: the Mw 7.1 September 4, 2010 Darfield and the Mw 6.2 February 22, 2011 Christchurch earthquakes. A structured format, based on internationally recognised taxonomies and damage descriptors, is introduced to present the assets and to report on the earthquake-induced physical impacts for both above-ground and underground components. Functional impacts, interdependency issues and resilience attributes observed during the emergency management and recovery phases for the same infrastructure systems are furthermore discussed in the paper. It is envisaged that the data and overview on the seismic performance and management of infrastructure systems presented in the paper can be used to test the effectiveness of existing models and to inform the development of new models for seismic risk assessment and resilience analysis. Also, the structured framework presented within this paper can form the basis for defining specific and standardised survey tools for post-earthquake assessment of infrastructure systems.

Framework for Seismic Hazard Analysis of Spatially Distributed Systems

The analysis of seismic risk to multiple systems of spatially distributed infrastructures presents new challenges in the characterisation of the seismic hazard input. For this purpose a general procedure entitled “Shakefield” is established, which allows for the generation of samples of ground motion fields for both single scenario events, and for stochastically generated sets of events needed for probabilistic seismic risk analysis. For a spatially distributed infrastructure of vulnerable elements, the spatial correlation of the ground motion fields for different measures of the ground motion intensity is incorporated into the simulation procedure. This is extended further to consider spatial cross-correlation between different measures of ground motion intensity. In addition to the characterisation of the seismic hazard from transient ground motion, the simulation procedure is extended to consider secondary geotechnical effects from earthquake shaking. Thus the Shakefield procedure can also characterise the effects site amplification and transient strain, and also provide estimates of permanent ground displacement due to liquefaction, slope displacement and coseismic fault rupture.

Application to L’Aquila Gas Network

This chapter, after an introduction presenting the general framework for the seismic risk assessment of a gas network according to the SYNER-G methodology (Chap. 2), describes the case study of L’Aquila (central Italy) gas distribution system, a 621 km pipeline network managed by Enel Rete Gas s.p.a. and operating at medium- and low-pressure. Subsequently, the main features regarding the implementation of the application study within the SYNER-G framework are reported, and the process for the seismic performance characterization is summarized. Then, the risk analysis of the system is described, and results in terms of connectivity-based performance indicators are presented.