http://www.glaciology.ethz.ch ICEQUAKES AS PRECURSORS OF ICE AVALANCHES
نویسنده
چکیده
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.
منابع مشابه
Intermediate-depth icequakes and harmonic tremor in an Alpine glacier (glacier d 'Argentiere,France): evidence for hydraulic fracturing
We detected several thousand deep englacial icequakes on Glacier d’Argentière (Mont-Blanc Massif) between 30 March and 3 May 2012. These events have been classified in eight clusters. Inside each cluster, the waveforms are similar for P-waves and S-waves, although the time delay between the P-waves and S-waves vary by up to 0.03 s, indicating an extended source area. Although these events were ...
متن کاملPrecursory seismicity associated with frequent, large ice avalanches on Iliamna volcano, Alaska, USA
Since 1994, at least six major (volume >10m) ice and rock avalanches have occurred on Iliamna volcano, Alaska, USA. Each of the avalanches was preceded by up to 2 hours of seismicity believed to represent the initial stages of failure. Each seismic sequence begins with a series of repeating earthquakes thought to represent slip on an ice–rock interface, or between layers of ice. This stage is f...
متن کاملAssessment of the hazard potential of ice avalanches using remote sensing and GIS-modelling
Ice avalanches typically occur when a large mass of ice breaks off from steep glaciers. Since the reach of ice avalanches is usually low, their hazard potential is generally restricted to high mountain areas that are densely populated or frequently visited by tourists. However, far-reaching disasters are possible in combination with other processes such as rockfalls or snow avalanches. In addit...
متن کاملMonitoring and modeling ice-rock avalanches from ice-capped volcanoes: A case study of frequent large avalanches on Iliamna Volcano, Alaska
Iliamna is an andesitic stratovolcano of the Aleutian arc with regular gas and steam emissions and mantled by several large glaciers. Iliamna Volcano exhibits an unusual combination of frequent and large ice-rock avalanches in the order of 1×10 m to 3×10 m with recent return periods of 2–4 years. We have reconstructed an avalanche event record for the past 45 years that indicates Iliamna avalan...
متن کامل