DETERMINING ORIGIN AND MECHANISM OF MICROSEISMIC EVENTS IN THE EARTHS SUBSURFACE BY DEVIATORIC MOMENT INVERSION

摘要

A method for locating origin time, origin location and source mechanism of seismic events occurring in a selected volume of subsurface formations includes calculating a travel time from each possible origin location to each of a plurality of seismic receivers disposed above the volume in a selected pattern. A signal amplitude is measured by each receiver for each possible origin time at each possible origin location. The signal amplitude is determined from the continuously recorded data by calculating travel time delays for each possible origin location and origin time. The deviatoric moment tensors are determined from the signal amplitudes by moment tensor inversion restricted to deviatoric moment tensors. A norm for each deviatoric moment tensor is generated. An origin time, origin position and source mechanism of a seismic event is determined wherein any norm exceeds a selected threshold.