1. A method for mapping a fracture network from microseismic signals, comprising: determining a source of at least one seismic event from features in the signals exceeding a selected amplitude (“visible seismic event”), the signals generated by recording output of a plurality of seismic receivers disposed proximate a volume of the Earth's subsurface to be evaluated, the signals being electrical or optical and representing seismic amplitude; determining a source mechanism of the at least one visible seismic event; determining a fracture size and orientation from the source mechanism; determining seismic events from the signals from features less than the selected amplitude (“invisible seismic events”) using a stacking procedure; determining a source mechanism for the invisible seismic events by matched filtering; defining at least one fracture from the invisible seismic events; and generating a fracture network model by combining the at least one fracture determined from the visible seismic event with the at least one fracture determined from the invisible seismic events.