Geomechanics of Microseismic Deformation
Microseismic sources and emission of the detected seismic waves are an expression of some aspects of the complete geomechanical deformation of the hydraulic-fracture network. Specific signal attributes can be analyzed to estimate source characteristics of the episode of coseismic fracture deformation that corresponds to generation of the microseismic source. Amplitude characteristics of the seismic signal are related to the source strength or magnitude of the microseismic event. Frequency content can be related to the slip duration and hence the source radius or slip area. Other aspects such as stress release and energy flux also can be estimated. Finally, the directivity or radiation pattern of the relative amplitudes and first motion can be used to investigate the microseismic source mechanism, including mode of fracturing (i.e., tensile opening or shear deformation), fracture-plane orientation, and principle stresses leading to the failure.