SignificanceGeologic carbon storage remains a safe option to mitigate anthropogenic climate change. Properly sited and managed storage sites are unlikely to induce felt seismicity because (i) sedimentary formations, which are softer than the crystalline basement, are rarely critically stressed; (ii) the least stable situation occurs at the beginning of injection, which makes it easy to control; (iii) CO2will dissolve into brine at a significant rate, reducing overpressure; and (iv) CO2will not flow across the caprock because of capillarity, but brine will, which will reduce overpressure further. Furthermore, CO2leakage through fault reactivation is unlikely because the high clay content of caprocks ensures a reduced permeability and increased entry pressure along localized deformation zones.