Wavefield inversion for microseismic imaging
Résumé
Full waveform inversion (FWI) has recently received lots of attention for microseismic event characterization. However, FWI with unknown sources becomes severely underdetermined, hence requiring strong prior information. The frequency-domain wavefield inversion method (WRI) has shown promising results to mitigate the FWI nonlinearity generated by cycle-skipping. WRI relies on the reconstruction of data-assimilated wavefields, which approach the true wavefield near the receivers, a helpful feature when the source is added as a new variable. We present an adaptation of WRI that reconstructs the wavefields, the sources, and the subsurface model. The method does not require a prior assumption on the number of events. The inversion is stabilized by sparsifying regularizations tailored to the source and velocity model subproblems. The method tested on the Marmousi model using two clusters of sources which are successfully located.