Abstract | A seismic vulnerability estimation procedure is developed for liquid storage tank-farms, specifically ensembles of atmospheric tanks that are interconnected to provide enhanced storage capacity for a given liquid product. All pertinent sources of uncertainty are considered together with associated intra-and inter-structure correlations, while particular attention is paid to the effect of uncertainty on damage state threshold values. Appropriate decision variables are defined in view of enabling decision-making for the mitigation of seismic losses at the level of the system, rather than the individual structure, focusing on (a) the leakage of stored product and (b) the loss of storage capacity. A case study of nine tanks, evenly split in three types, is undertaken. Whenever uncertain damage state thresholds are considered, Monte-Carlo simulations reveal a significant potential for loss of containment for average spectral accelerations (AvgSa) of 0.30g. While storage capacity is proportionately impacted, a remarkable 30% of the total farm storage volume can survive an AvgSa of 0.5g, thus leaving considerable room for the drainage and repair of damaged tanks in typical operation scenarios.