Systems and methods for distributed interferometric acoustic monitoring

A method for distributed acoustic detection or monitoring of activity, comprising:

• transmitting a monitoring signal through a fiber optic cable, wherein the monitoring signal comprises a pulse of a coherent beam of electromagnetic radiation where a coherence time of the coherent beam of electromagnetic radiation is equal to or longer than a time duration of the pulse, and wherein the fiber optic cable is disposed in a subterranean section of the Earth;
• detecting coherent Rayleigh noise generated by the transmission of the coherent beam of radiation through the fiber optic;
• processing the detected coherent Rayleigh noise to identify one or more acoustic occurrences in the subterranean section of the Earth;
• and
• monitoring or detecting the activity using the identified one or more acoustic occurrences.