The methods described are for determining distribution, orientation and dimensions of networks of hydraulically- induced fractures within a subterranean formation containing fluids. Micro-seismic events are generated, after cessation of fracturing and establishment of fracture networks, by particles introduced into the fractures which are capable of explosive or chemical reaction. In one method, attachment site particles are positioned within the formation during fracturing and additional reactive particles are later introduced. The reactive particles attach to the attachment sites and, upon a triggering event, react to produce micro-seismic events. The waves generated by the micro-seismic events are used to provide mapping of the effective fracture space. Additionally, time-lapse mapping is provided with use of "species" of attachment sites and reactive particles.