1. A method for mapping a fracture network from microseismic signals, comprising: determining in a computer a source of at least one seismic event from features in the signals when the signals exceed 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 in the computer, the source mechanism consisting of a source moment (M 0 ) and a dip, a strike and rake of the at least one visible seismic event, a volumetric change and a compensated linear vector dipole; determining a fracture size and orientation from the source mechanism in the computer; determining seismic events from the signals from features when the signal amplitude is less than the selected amplitude (“invisible seismic events”) in the computer using a stacking procedure; determining a source mechanism for the invisible seismic events by matched filtering in the computer; defining at least one fracture from the invisible seismic events in the computer; and generating a fracture network model in the computer by combining the at least one fracture determined from the visible seismic event with the at least one fracture defined from the invisible seismic events.