Source wavelet estimation using common mid-point gathers

Abstract

The source wavelet estimation is a crucial process for full waveform inversion because we can hardly know source information from observed data. In order to implement the full waveform inversion in the common mid-point (CMP) domain, source wavelet estimation may be performed using CMP gathers for efficiency and consistency. In this paper, we introduce the source wavelet estimation using CMP gather data. Since the CMP gather is the time–domain data, the source wavelet is transformed into the frequency domain to apply full Newton method. Finally, it is transformed back into the time domain. Through numerical examples, we show how sensitive the source wavelet inversion is to both the direct waves on CMP gathers and the uncertainty of initial velocity. We can succeed in accurately estimating source wavelet if we introduce time damping and the CMP data has direct waves in spite of an incorrect initial velocity. This is because direct waves, which are key elements for source estimation, propagate through water layer of which velocity information is precisely known. Therefore, we have to exploit direct wave for successful source wavelet estimation in full waveform inversion.