Validity Domain of the Born Approximation for Seismic Waveform Modelling in Realistic 3-D Earth Structure

parisi, laura ; ferreira, ana m. g ; capdeville, yann;

While the first-order Born approximation is incre a singly being used in many seismic tomography efforts, its domain of validity to forward model seismic wave forms has not been quantified in the context of current 3-D earth models yet. We here address this issue by comparing teleseismic synthetic surface waveforms calculated using the Born approximation with spectral element method solutions for a variety of realistic global 3-D earth models. We find that the Born approximation has a very limited domain of validity when applied to seismic wave forms. Specifically, it can only accurately model the phase (amplitude) of surface waveforms for source–receiver paths leading to time shifts smaller than about 15 per cent (5 per cent) of the wave period considered. These conditions usually occur in earth models as S20RTS or S40RTS combined with a homogeneous crust for periods longer than T ∼ 80–90 s. For models with stronger heterogeneity and/orrealistic3-D crustal structure, only the phase of wave forms with periods longer than∼120–130 s can be accurately modelled with the Born approximation.