A method of generating a micro-seismic event in a medium from a non-linear interaction to characterize the medium, the method comprising: generating, by a first acoustic source, a first coded acoustic signal; generating, by a second acoustic source, a second coded acoustic signal; wherein the first acoustic source and the second acoustic source are controllable such that trajectories of the first and the second acoustic signals intersect in a mixing zone within the medium; receiving, by a receiver, a detected signal including a third signal being generated by a non-linear mixing process from the first acoustic signal and the second acoustic signal in the mixing zone; performing, by a processor, data processing on the received signal, or correlating with a coded signal template, or both, to extract the third signal generated by the non-linear mixing process over noise or over signals generated by a linear interaction process, or both, to obtain an emulated micro-seismic event signal occurring at the mixing zone of the first and second acoustic signals; and characterizing properties of the medium or creating a 3D image of the properties of the medium based on the emulated micro-seismic event signal, characterized in that: the first acoustic signal comprises a first plurality of pulses arranged as a time sequence, the first plurality of pulses being separated in time, each pulse comprising a modulated signal at a central frequency, wherein central frequencies of two consecutive pulses are different; and the second coded acoustic signal comprises a second plurality of pulses arranged as a time sequence, the second plurality of pulses being separated in time, wherein a separation in time between centers of two consecutive pulses is the same as a separation in time between centers of two corresponding pulses in the first plurality of pulses, wherein a start time difference is provided between a start time of a broadcast of the second plurality of pulses and a start time of a broadcast of the first plurality of pulses, wherein each pulse comprises a modulated signal and a central frequency of the modulated signal within each pulse in the second plurality of pulses is a selected fraction d of the central frequency of the modulated signal for the corresponding pulse in the first plurality of pulses. generating, by a first acoustic source, a first coded acoustic signal; generating, by a second acoustic source, a second coded acoustic signal; wherein the first acoustic source and the second acoustic source are controllable such that trajectories of the first and the second acoustic signals intersect in a mixing zone within the medium; receiving, by a receiver, a detected signal including a third signal being generated by a non-linear mixing process from the first acoustic signal and the second acoustic signal in the mixing zone; performing, by a processor, data processing on the received signal, or correlating with a coded signal template, or both, to extract the third signal generated by the non-linear mixing process over noise or over signals generated by a linear interaction process, or both, to obtain an emulated micro-seismic event signal occurring at the mixing zone of the first and second acoustic signals; and characterizing properties of the medium or creating a 3D image of the properties of the medium based on the emulated micro-seismic event signal, the first acoustic signal comprises a first plurality of pulses arranged as a time sequence, the first plurality of pulses being separated in time, each pulse comprising a modulated signal at a central frequency, wherein central frequencies of two consecutive pulses are different; and the second coded acoustic signal comprises a second plurality of pulses arranged as a time sequence, the second plurality of pulses being separated in time, wherein a separation in time between centers of two consecutive pulses is the same as a separation in time between centers of two corresponding pulses in the first plurality of pulses, wherein a start time difference is provided between a start time of a broadcast of the second plurality of pulses and a start time of a broadcast of the first plurality of pulses, wherein each pulse comprises a modulated signal and a central frequency of the modulated signal within each pulse in the second plurality of pulses is a selected fraction d of the central frequency of the modulated signal for the corresponding pulse in the first plurality of pulses.