Source Wavelet Amplitude Spectrum Estimation Using Marchenko Focusing Functions

Marchenko focusing enables the redatuming of seismic surface data to an arbitrary new datum level in the subsurface. One requirement for an accurate redatuming is the correct deconvolution of the source signature from the acquired surface reflection response. Using an erroneous source wavelet for deconvolution leads to inaccurate redatuming and, thus, to artefacts in the redatumed data. However, the true amplitude spectrum of the source wavelet is often unknown. We propose a novel approach to invert for the amplitude spectrum of the source wavelet using focusing functions obtained by the Marchenko redatuming process. Deconvolving the data with an incorrect source wavelet generates undesired coda events in the focusing function. We identify such coda events by the analysis of an ensemble of focusing functions, where differently scaled source wavelets are used for deconvolution prior to redatuming. The amplitude spectrum of the identified coda is strongly related to an error in the source wavelet. Thus, we can iteratively invert for the correct scaling of the source wavelet by analyzing the amplitude spectrum of coda events in the focusing function. This approach yields the correct scaling of the amplitude spectrum of the source wavelet and enables accurate Marchenko redatuming.