Reliability of Seismic Moment Tensor Inversions for Induced Microseismicity at Kidd Mine, Ontario

Abstract

Ð A novel seismic moment tensor inversion approach is applied to microseismic events from the Kidd mine with moment magnitudes ranging between À1.2 and 0. Data consist of 35 events recorded on 8 triaxial accelerometers installed underground. Reliable solutions are obtained for 21 events, of which 14 represent pure shear mechanisms, whereas the remaining 7 exhibit a signi®cant positive volumetric component (72±76%), along with some pure shear failure (15±20%). Further analysis indicates that 6 of the events characterized by high volumetric components are located within a sill pillar on the 4,700 level and have subvertical P and subhorizontal T axes. This is in agreement with the presence of tensile cracks close to openings for incipient pillar bursting. The pure shear events are located outside the sill pillar, between the 4,600 and 4,800 levels, and on the 5,600 level within a highly fractured rockmass. For the latter events, the subvertical nodal planes are found to match closely the orientation of subvertical NW-SE fractures aligned parallel to the major faults in the area.

On the retrieval of moment tensors from borehole data

“…This can be achieved by an experiment with at least two monitoring boreholes and by processing both P‐ and S‐waves. Optimally, the inversion for the complete moment tensor should be supplemented by estimates of their reliability and by error analysis (Šílený 1998; Trifu, Angus and Shumila 2000; Trifu and Shumila 2002; Šílený 2004).…”

“…They are analysed by detection algorithms, and the events are traced to image fracturing as a function of time. Seismic waveforms are used to determine the source–time functions and moment tensors, which provide information about the size and orientation of fractures (Rutledge, Phillips and Schuessler 1998; Nolen‐Hoeksema and Ruff 2001; Trifu and Shumila 2002; Rutledge and Phillips 2003). The moment tensors also indicate whether the fracture is opening or closing, which is the key to monitoring the connectivity of the fracture (Ross, Foulger and Julian 1999; Maxwell and Urbancic 2001; Foulger et al 2004).…”

Waveform inversion and analysis of an unusual earthquake swarm in the Boshan mining area, Shandong Province, China

“…Table 2 shows that, except for the three initial events, the proportion of the DC components in the events was very small (\60 %). Trifu and Shumila (2002) found that large non-DC components appeared in some mine were 15 %-20 %; their analysis showed that the moment tensor results were reliable. Dahm et al (2000) studied the accuracy of the seismic source mechanism by comparing the absolute and relative moment tensor solutions; they estimated the error caused by the medium model and inaccurate amplitude data.…”

“…For non-DC components in seismic moment tensor solutions, some seismic moment tensor analysis has shown Trifu and Shumila 2002;Horálek et al 2010) that, under certain circumstances (e.g., mine earthquakes due to reservoir filling, water injection in oil production, volcanic activity and geothermal eruption, landslides, collapses, and subsidence), the non-DC components (the CLVD and ISO components) may form a large proportion of the total. Julian et al (1998) force system and systematically analyzed the possible physical processes of non-DC earthquakes.…”

Acoustic emission induced by progressive excavation of an underground powerhouse

“…With regard to induced seismicity in metal mines excavated from 1400 to 3500 m deep, fracture mechanisms are often identified by using the fault-plane solution and moment tensor inversion [1][2][3]. These methods are also applied to the identification of fracture mechanisms in coal mines, which have relatively shallow depths from 600 to 1500 m but also have much larger volume excavations, thereby inducing stress concentrations of the same approximate intensity as deep metal mines [4][5][6].…”