Seismic Resilience Evaluation of Fixed Communication Infrastructure Systems

Abstract

The reliability and availability of lifelines during and after any natural hazard-caused disaster is a critical requirement to ensure that society can not only tolerate the effects of natural disaster but also recover to its pre-disaster state as fast as possible. The fixed communication infrastructure systems play a vital role not only during everyday life but also during and after natural disasters to provide communication with emergency services and to support the recovery of other lifelines due to inherent interdependencies. The major objectives of this research are: • Quantitative assessment of the impact of major earthquakes on fixed communication infrastructure and development of geospatial seismic hazard maps for the lifeline; • Quantitative seismic resilience evaluation of the fixed communication system; and • Guidelines and approaches to enhance the seismic resilience of the fixed communication infrastructure network. The study explores both the seismic induced physical damages to the fixed communication infrastructure systems and the degradation of the communication systems performance due to high surge in traffic demand which results in congestion during and after an earthquake. In this thesis, the approaches and methods are motivated by the seismic risk assessment (SRA) and Resilience-Compositional Demand Supply (Re-CoDeS) frameworks. This study validates these methods through a case study to assess the possible impact of four scenarios of Alpine Fault 8 (AF8) earthquake on the West Coast, New Zealand fixed communication infrastructure system. The AF8 seismic damages to central offices (COs) are modelled on GIS map to produce a seismic hazard map which aims to aid the investment strategies to enhance the resilience of the fixed communication infrastructure system. This study also uses the fragility functions of COs, which is a key input for the SRA. Based on the results and findings from the case study, it is found that as Modified Mercalli Intensity (MMI) level increases, the severity of damage to COs increases. A Southern Hypocenter AF8 scenario would result in extensive (ds2) or complete (ds3) damage to a greater number of COs than in any other AF8 earthquake scenarios. It is observed that there is a higher risk of losing Greymouth (T2 CO) in case of AF8 Central and Southern Hypocenter MMI 9 scenarios than the other two AF8 scenarios under study. Traffic tolerance (capacity) measured in Mbps is used as a metric for seismic resilience evaluation. It can also be concluded that the West Coast fixed communication infrastructure system would have high seismic resilience (Rsys) for MMI 8 level for AF8 Central and Southern Hypocenter compared to MMI level 9.