Methods and systems for investigating a formation surrounding a wellbore. The methods involve a semblance-based analysis of downhole data, for example low frequency downhole data. The semblance-based analysis includes group semblance mapping of the data, followed by single shot semblance map handling, followed by multiple shot data handling. The systems include a seismic source, a seismic receiver, and an electronics system for processing data according to a process including: group semblance mapping, single shot map handling, and multiple shot data handling. The seismic source may generate low frequency signals, and the seismic receiver may be two or more receiver subsystems that include at least two axially spaced-apart hydrophones and at least one multi-component geophone.