Abstract: For offshore wind turbines (OWTs) nearing the end of their service life, repowering with modern high-efficiency turbines is a preferred strategy that maximizes the use of existing foundations and enhances energy efficiency, enabling sustainable reutilization of aging wind farms. To address the engineering challenges of repowering jacket-supported OWTs, this study conducts centrifuge shaking table tests on a tripod bucket jacket foundation in saturated sand, aiming to compare the seismic response of OWT systems before and after repowering. White noise excitation and seismic motions of varying amplitudes are applied to evaluate key parameters, including natural frequency, excess pore water pressure, acceleration response, and deformation characteristics. Results show that the increased nacelle mass of the repowered system induces stronger inertial motion under seismic excitation, leading to greater excess pore pressure accumulation, higher peak rotational deformation, and amplified acceleration responses. Meanwhile, additional stress and constraint from the bucket reduce the acceleration response and pore pressure accumulation inside the bucket compared to the outside, partially filtering high-frequency components. Furthermore, the repowering strategy substantially amplifies horizontal rotational deformation but has limited influence on vertical settlement. These findings provide a theoretical basis for assessing the seismic performance of repowered OWT systems.