Slope stability monitoring from microseismic field using polarization methodology
Numerical simulation of seismoacoustic emission (SAE) associated with fracturing in zones of shear stress concentration shows that SAE signals are polarized along the stress direction. The proposed polarization methodology for monitoring of slope stability makes use of three-component recording of the microseismic field on a slope in order to pick the signals of slope processes by filtering and polarization analysis. Slope activity is indicated by rather strong roughly horizontal polarization of the respective portion of the field in the direction of slope dip. The methodology was tested in microseismic observations on a landslide slope in the Northern Tien-Shan (Kyrgyzstan).
Icequakes as precursors of ice avalanches
A hanging glacier at the east face of Weisshorn broke off in 2005. We were able to monitor and measure surface motion and icequake activity for 21 days up to three days prior to the break-off. Results are presented from the analysis of seismic waves generated by the glacier during the rupture maturation process. Three types of precursory signals of the imminent catastrophic rupture were identified: (i) an increasing seismic activity within the glacier, (ii) a change in the size-frequency distribution of icequake energy, and (iii) a log-periodic oscillating behavior superimposed on power law acceleration of the inverse of waiting time between two icequakes. The analysis of the seismic activity gave indications of the rupture process and led to the identification of two regimes: a stable one where events are isolated and non correlated which is characteristic of diffuse damage, and an unstable and dangerous one in which events become synchronized and large icequakes are triggered.
The Motor Rewind Issue-A New Look
Motor users have always been concerned about how long a rewound motor would last but never knew what to do about it. As power costs become higher and higher, a new and related question is cost. What happens to the efficiency and operating cost of a motor that is rewound two to three tithes during, its lifetime? The answers will depend upon how the motor is repaired. How motor losses can be changed during the rewind process is reviewed, along with what precautions should be taken to prevent an increase in operating costs and a decrease in motor life. The positive steps the motor user can take to protect his motor investment will also be explored.