Enhancing structural resilience to sequential earthquakes: Lessons from recent earthquake sequences and low-damage seismic design strategies

Earthquake risk is commonly evaluated on the basis of individual design events, yet real seismic crises may involve mainshock-aftershock sequences, earthquake doublets, or multiple strong motions separated by minutes, days, or months. When a structure is already damaged by a preceding event, the next earthquake acts on a modified structural system with potentially reduced stiffness, strength, altered load paths, residual drift, and compromised nonstructural and infrastructure components. This working paper reviews the cumulative consequences of sequential earthquakes and examines two complementary damage-control strategies: limiting structural demand so that the primary system remains predominantly elastic, and decoupling the superstructure from damaging ground motion through seismic base isolation. Lessons from the 2016–2017 Central Italy sequence, the 2010–2011 Canterbury sequence, and the 2023 Kahramanmaras earthquake sequence illustrate the importance of considering the pre-damaged state of buildings, lifelines, and communities. The paper then discusses the implications of using a response modification factor of R = 1 as an intentional elastic-design strategy, while emphasizing that R = 1 should not be interpreted as an automatic guarantee of zero cracking or zero damage unless explicit performance criteria are satisfied. Base isolation is reviewed as a complementary approach that increases horizontal flexibility at the isolation interface, shifts the effective period, and can reduce transmitted acceleration while accommodating controlled displacement. The overall argument is that seismic resilience under repeated earthquakes is better served by a performance-based, damage-control philosophy that combines appropriate force levels, stiffness, damping, isolation, self-centering, replaceable energy-dissipation components, and post-earthquake inspection and repair planning. A final section proposes recommendations for code development, design practice, and resilience planning, with particular attention to urban areas exposed to closely spaced seismic events.