2017_EJRNL_PP_GANGWON_JEONG_1.pdf
Terbatas  
» Gedung UPT Perpustakaan
Terbatas  
» Gedung UPT Perpustakaan
To reconstruct long-wavelength structures in full waveform inversion (FWI), the wavefield-damping and
weighting techniques have been used to synthesize and emphasize low-frequency data components in
frequency-domain FWI. However, these methods have some weak points. The application of wavefielddamping method on filtered data fails to synthesize reliable low-frequency data; the optimization formula
obtained introducing the weighting technique is not theoretically complete, because it is not directly derived
from the objective function. In this study, we address these weak points and present how to overcome them.
We demonstrate that the source estimation in FWI using damped wavefields fails when the data used in the
FWI process does not satisfy the causality condition. This phenomenon occurs when a non-causal filter is applied
to data. We overcome this limitation by designing a causal filter. Also we modify the conventional weighting
technique so that its optimization formula is directly derived from the objective function, retaining its original
characteristic of emphasizing the low-frequency data components. Numerical results show that the newly
designed causal filter enables to recover long-wavelength structures using low-frequency data components
synthesized by damping wavefields in frequency-domain FWI, and the proposed weighting technique enhances
the inversion results