Theoretical Assessment of the full-moment-tensor resolvability for receiver arrays used in microseismic monitoring
Abstract
An inversion of full moment tensors representing source mechanisms is becoming routinely used when interpreting microseismic monitoring. However, a stability of such inversion varies significantly for different receiver arrays.
Unlike stability of location, which is hard to assess, the stability of inverted full moment tensor can be measured by a condition number. We tested three types of receiver arrays (dense surface array, dual borehole array and multi-borehole array) used in the microseismic monitoring and computed the theoretical stability of full moment tensor inversion from P-or P-and S-wave amplitudes at areas of interest.
We analyzed a 3D distributions of the condition numbers and show that with surface and multi-borehole arrays of receivers we are capable of inverting stable source mechanisms for the events located at depths comparable to the maximum offset of receivers, but shallower events and the events at the depths of the borehole arrays are poorly constrained. This study provides a guidance for a quick prediction of source mechanism inversion quality.
Computing condition numbers does not require any information about the data, it measures a theoretical quality of the moment tensor inversion. The computed condition numbers represent inversion for ideal dataset with the selected geometry.