Three Dimensional Attenuation Tomography from microseismicity

Attenuation images are obtained from 6287 t-star spectral measurements of P-wave microseismic events in a mine setting. The resulting three-dimensional quality factor (Q) model reveals that most of the study region is characterized by low Q values or high attenuation (Q<25), probably caused by cavities and fractures due to mining activities. Q values between 25 and 50 show a high spatial correlation with the location of an ore deposit. Furthermore, high quality ore deposits correlate with Q values of about 45-50 whereas the low quality ore correlates with Q values of around 30. Q values of less than 10 correlate with the observed seismic cloud epicenters. These features were previously partially resolved by velocity tomography. Therefore a joint interpretation is very important in determining the lithological properties and physical state of both, the region containing the seismic epicenters and the region with the ore deposits. The same methodology is applicable to microseismic data recorded during hydraulic fracturing treatment and may give more insight into fracture density of hydrocarbon reservoirs.