A Framework to Evaluate the Benefit of Seismic Upgrading Panagiotis Galanis, a) M.EERI, Anastasia Sycheva, b) Wanda Mimra, c) and Božidar Stojadinović, d) M.EERI Earthquakes are among the most catastrophic natural disasters. Existing buildings constructed in earthquake prone locations prior to 1970s generally do not meet the criteria of modern seismic design codes. Structural seismic upgrading is a very effective strategy to mitigate the earthquake risk for existing structures. However, in many cases, seismic upgrade design is criticized as overly conservative resulting in expensive structural interventions. The present study proposes a framework that combines key elements of the performance-based seis- mic design with the actuarial “frequency-severity” method to perform a cost- benefit analysis of structural seismic upgrading. A curve that quantifies the avoided losses and casualties for different levels of partial seismic upgrade at the site of interest is introduced. This curve provides a tool that enables engineers to optimize rapidly, at a preliminary design level, the seismic upgrading strategy using a cost-benefit analysis. The proposed framework is applied to existing resi- dential buildings located in two different seismic hazard environments, namely Zurich (Switzerland) and L’Aquila (Italy), to identify the optimal seismic upgrad- ing level. [DOI: 10.1193/120316EQS221M] INTRODUCTION Earthquakes are among the most feared natural hazards: they are unpredictable, and they cause loss of lives and direct damage to the built infrastructure. Furthermore, earthquakes have substantial indirect consequences with cascading and systemic effects, such as business interruption, loss of employment, decreased tax revenues, impaired institutional capacity and a rise in poverty levels. Thus, developing holistic strategies for mitigation and management of seismic risk is of critical importance. A well-developed understanding of the likelihood and potential impacts of earthquake hazard provides the basis for elaborating and assessing the full range of risk management strategies aimed at mitigating the adverse consequences of disastrous earthquake events. One of the main earthquake risk management strategies is risk reduction. The objective is to reduce the seismic vulnerability of the affected structures and consequently the a) Research Associate, ETH Risk Center, Zurich, Switzerland 8092 b) Doctoral Student, ETH Zurich, Department of Management, Technology and Economics, Switzerland 8092 c) Professor, Chair of Risk and Insurance Economics, ETH Zurich, Switzerland 8092 d) Professor, Chair of Structural Dynamics and Earthquake Engineering, ETH Zurich, Switzerland 8092 Earthquake Spectra, Volume 34, No. 2, pages 527–548, May 2018; © 2018, Earthquake Engineering Research Institute 527