Generation of Orientation‐Independent Response Spectrum‐Matched Records Satisfying Minimum Fourier Amplitude and Power Spectral Density Requirements

The seismic design and assessment of critical infrastructure, particularly within the nuclear industry, relies heavily on acceleration time histories compatible with a design response spectrum (DRS). While current spectral matching algorithms effectively tune ground motions to match a target DRS, this process can inadvertently deplete the signal's energy at specific frequencies, leading to unstable and unconservative in‐structure response spectra (ISRS). To mitigate this, the U.S. Nuclear Regulatory Commission (US‐NRC) Standard Review Plan (SRP) 3.7.1 mandates a secondary check ensuring the motion satisfies a minimum power spectral density (PSD) requirement. However, while modern seismic hazard definitions have shifted toward orientation‐independent metrics (RotDnn), existing matching tools address PSD compliance only for single components. This article presents a unified algorithm that modifies bidirectional seed records to simultaneously match a target RotDnn response spectrum and satisfy minimum RotDnn Fourier amplitude spectrum (FAS) and PSD requirements. The methodology integrates the continuous wavelet transform (CWT) with an iterative multistage scaling process—combining global frequency adjustments for FAS compliance with localized time‐domain gains for PSD sufficiency. This approach allows for the generation of records that meet strict regulatory energy criteria while minimizing disruption to the nonstationary characteristics and directionality of the seed motions.