Scenario-Based Seismic Risk Assessment for Buried Transmission Gas Pipelines at Regional Scale

Abstract

Buried gas pipelines in seismic-prone regions may suffer leaks or breaks as a consequence of an earthquake, especially if the pipeline is subjected to large differential displacements due to geotechnical failures (e.g., landslide or liquefaction). This paper presents a methodology to assess the risk of a gas pipeline infrastructure at a regional level in the aftermath of a seismic event. Once earthquake characteristics, such as magnitude and epicenter, are known, seismic intensity measures (IMs), such as peak ground acceleration (PGA) and peak ground velocity (PGV), are estimated at the location of each pipe through a simulation-based procedure. The potential updating from real-time data coming from accelerometric stations is considered. These IMs are then used to study the cascading landslide and liquefaction hazards, providing a hybrid empirical-mechanical-based estimation of permanent ground displacements (PGD). With the aid of damage and fragility functions from the literature, loss figures and damage maps are derived as decision-support tools for network managers and stakeholders. Losses provide a preliminary estimation of repair costs, whereas damage maps support the prioritization of inspections in the aftermath of the event. The risk methodology is a novel combination of cutting-edge and consolidated approaches. Firstly, different crosscorrelation models between PGA and PGV are included. Secondly, a new three-phase back-to-back geotechnical approach is provided for both landslide and liquefaction, representing (1) the susceptibility, (2) the triggering, and (3) the PGD estimation phases. The 1976 Friuli earthquake and the high-pressure gas network of northeast Italy are used as a test-bed scenario for the risk methodology aimed at emphasizing pros and cons of the different alternative options investigated.

Seismic hazard for the Trans Adriatic Pipeline (TAP). Part 1: probabilistic seismic hazard analysis along the pipeline

“…Pipelines buried in earthquake-prone areas may leak or break following a seismic event, especially if the pipeline is affected by permanent ground displacement or strong transient ground jolts (Pyrras and Sextos 2018). Most of the damage reported to date is attributed to peak ground displacement (PGD; O'Rourke and Palmer 1996; Chen et al 2002), with possible failures triggered by active fault movements (Melissianos et al 2017), landslides, and liquefaction phenomena (De Risi et al 2018). Wave propagation effects can also contribute to pipe damage (Sakurai and Takanashi 1969;Esposito et al 2009; O'Rourke 2009), though to a lesser extent.…”

Earthquake Risk of Gas Pipelines in the Conterminous United States and Its Sources of Uncertainty

“…Empirical RR models are typically developed from observed damage to pipelines in past earthquakes and yield the average number of repairs per length of pipe, RRðv; θÞ. Given strong ground shaking, common practice is to assume that 80% of repairs corresponds to leaks, whereas 20% of repairs corresponds to breaks (FEMA 2012;Pineda-Porras and Najafi 2010;De Risi et al 2018) because repair records after earthquakes do not always provide enough information to distinguish between different damage states (O'Rourke 2014). Therefore, the RR functions in Eq.…”

“…There are both advantages and disadvantages to empirical RR models. For example, they are commonly used in regional seismic risk assessments of pipelines, including gas pipelines (Ameri and van de Lindt 2019;Esposito et al 2013Esposito et al , 2015Gehl et al 2014;Jahangiri and Shakib 2018;Mousavi et al 2014;De Risi et al 2018;Shabarchin and Tesfamariam 2017). Furthermore, they are developed empirically from observed damage in past earthquakes.…”

Seismic risk at urban scale: the role of site response analysis

“…First, it provides a quantification of the socio-economic impact of potential future earthquakes on densely-populated areas (Smerzini and Pitilakis, 2018), offering key information to relevant stakeholders such as engineers, insurers, reinsurers, brokers, capital market investors, and corporations. Second, it helps local and national governmental institutions (e.g., the civil protection) in planning effective policies of risk mitigation during peacetime (Cosenza et al, 2018) and improving the preparedness that is necessary during the emergency in the aftermath of a seismic event (De Risi et al, 2018).…”