1:45 PM - 2:00 PM
[S09-3-02] A NEW APPROACH TO FAULT ZONE SEISMIC MONITORING
The universal macroscopic parameter controlling the seismic efficiency of a slip on a fault is the shear stiffness or the rate of decreasing the resistance to shear during relative fault side displacement. An abrupt decrease of the fault shear stiffness, judging by the results of laboratory experiments, is caused by the presence of some minerals or watered clays in the fault principal slip zone. The decrease of stiffness inside a rock mass can be registered as an increase of the amplitudes of waves reflected from the fault zone, and thereafter as a decrease of the amplitudes of refracted waves.
Summarizing information about large-scale man-caused and tectonic earthquakes (structure of focal zones, triggering factors, mechanics of generation of different slip modes in faults, seismic efficiency, etc.) and methods of fault shear stiffness assessment allowed to elaborate a remote monitoring of potentially dangerous sections.
In order to test the measuring techniques and the principles of the observation system arrangement, measurements were set up in the pit of the "Korobkovskoe" deposit of ferruginous quartzites (Kursk Magnet Anomaly, Russia). Deformation and seismic measurements in the pit were held on two faults of different scales: the local one (about 50 cm thick) and the regional one (about 100 m thick). Relative displacements, accelerations and velocities of fault sides under the action of seismic waves produced by explosions in the quarry and in the pit were recorded. Durations of both disturbances were actually the same but the noticeable difference array reaction was noted on these two types of sources.
The change of waveforms caused by passage through a tectonic discontinuity was registered.
Records of the deformograph showed creep and slow events - abrupt changes of deformation character (failures) during which the deformation rate increases noticeably, but doesn't reach values intrinsic for normal earthquakes.
Summarizing information about large-scale man-caused and tectonic earthquakes (structure of focal zones, triggering factors, mechanics of generation of different slip modes in faults, seismic efficiency, etc.) and methods of fault shear stiffness assessment allowed to elaborate a remote monitoring of potentially dangerous sections.
In order to test the measuring techniques and the principles of the observation system arrangement, measurements were set up in the pit of the "Korobkovskoe" deposit of ferruginous quartzites (Kursk Magnet Anomaly, Russia). Deformation and seismic measurements in the pit were held on two faults of different scales: the local one (about 50 cm thick) and the regional one (about 100 m thick). Relative displacements, accelerations and velocities of fault sides under the action of seismic waves produced by explosions in the quarry and in the pit were recorded. Durations of both disturbances were actually the same but the noticeable difference array reaction was noted on these two types of sources.
The change of waveforms caused by passage through a tectonic discontinuity was registered.
Records of the deformograph showed creep and slow events - abrupt changes of deformation character (failures) during which the deformation rate increases noticeably, but doesn't reach values intrinsic for normal earthquakes.