Seismic Resilience of a Crude Oil Refinery Unit—Downtime, Recovery, and Risk Assessment

ABSTRACT Seismic resilience is assessed for a hydrodesulphurization unit of a midsize crude oil refinery, with a focus on both direct physical damage and indirect business interruption (BI) losses. The aim is to develop a rigorous analytical methodology for assessing interconnected crude oil refinery units via tailored risk metrics. This study focuses exclusively on earthquake‐induced direct and indirect economic losses, whereas material release and its potential consequences, including damage propagation (e.g., domino effects), will be addressed in a dedicated study. First, the structural performance of the constituent assets is evaluated by means of multiple‐stripe analysis using hazard‐consistent ground motions. Detailed asset‐level damages are evaluated, followed by a repair workflow to enable a comprehensive quantification of recovery and economic impact. As even moderate damage to supporting systems, such as piping or instrumentation, can lead to prolonged downtime, direct physical damage accounts for only 1.2% of the total average annual loss (AAL), while BI indirect losses account for the remaining 98.8%. In this, modelling and analysis choices can be key: (i) the granularity of risk assessment (record‐based vs. fragility‐based), (ii) capacity correlation among identical assets, and (iii) operational conditions in terms of tank fill levels. While the coarse fragility‐based approach yields similar AALs compared to the detailed record‐based approach when hazard consistency is maintained, assumptions about capacity correlation and, more significantly, operational conditions have a substantial impact on risk estimates. Findings emphasize the need to prioritize continuity strategies, for example, redundancy and rapid restart, over asset hardening alone.