Low-frequency marine seismic data reconstruction based on the far-field signature using a modified U-Net

Abstract

Preserving low-frequency components in seismic data is challenging due to data acquisition restrictions and the processing of low-cut filtering after surveys. If seismic data lack low frequencies, their resolution deteriorates, leading to inaccurate seismic interpretations. To resolve this problem, we developed a low-frequency reconstruction that employs a modified U-Net neural network. To improve the training of the neural network, we generated training data analogous to unseen data, based on the far-field signature as the wavelet source to retain the spectral characteristics of field data. We addressed potential overfitting by generating a large amount of various synthetic data through wave equation-based modelling using a variety of velocity and density models. After synthesising the seismic data, we implemented a filtering method to produce input data with insufficient low frequencies and label data with sufficient low frequencies. The far-field signature plays an important role in the successful reconstruction of low frequencies due to its intrinsic field data features and greater low-frequency information compared to field data alone. We tested the generalisation of the network using unseen synthetic and field data not used in the training stage, and analyzed the results in the time and frequency domains. Although the input data did not retain frequencies below 10 Hz, the trained network predicted low frequencies that were similar to the desired data. We also produced post-stack sections via simple processing to evaluate low-frequency reconstructions produced by our trained network. The low-frequency reconstruction scheme led to a better understanding of subsurface media.