Response spectra are of fundamental importance in earthquake engineering
and represent a standard measure in seismic design for the assessment of structural
performance. However, unlike Fourier spectral amplitudes, the relationship of response
spectral amplitudes to seismological source, path, and site characteristics is not
immediately obvious and might even be considered counterintuitive for high oscillator
frequencies. The understanding of this relationship is nevertheless important for
seismic-hazard analysis. The purpose of the present study is to comprehensively characterize
the variation of response spectral amplitudes due to perturbations of the causative
seismological parameters. This is done by calculating the absolute parameter
sensitivities (sensitivity coefficients) defined as the partial derivatives of the model
output with respect to its input parameters. To derive sensitivities, we apply algorithmic
differentiation (AD). This powerful approach is extensively used for sensitivity analysis
of complex models in meteorology or aerodynamics. To the best of our knowledge, AD
has not been explored yet in the seismic-hazard context. Within the present study, AD
was successfully implemented for a proven and extensively applied simulation program
for response spectra (Stochastic Method SIMulation [SMSIM]) using the TAPENADE
AD tool. We assess the effects and importance of input parameter perturbations on the
shape of response spectra for different regional stochastic models in a quantitative way.
Additionally, we perform sensitivity analysis regarding adjustment issues of groundmotion
prediction equations.