Triggering mechanisms of Gayari avalanche, Pakistan

Abstract

A massive snow avalanche occurred on April, 2012 at Gayari, located in NE part of Pakistan, close to India and China Border. The catastrophic avalanche killed nearly 148 people, majority of which were Pakistan army personnel destroying army base camp. To mitigate its future hazard, different triggering mechanisms have been investigated in this study. We contemplate that the avalanche was triggered due to snow pack existence on favorable slope in combination with different meteorological conditions and anomalous ground vibration. The avalanche occurrence clock was advanced by two earthquakes: M4.1 at a distance ∼ 125 km that occurred about 21 hours before and another comparatively larger (M5.6) earthquake that occurred comparatively at larger distance (∼ 370 km) and longer time (∼ 25 days) before which have significantly changed the loading conditions. The latter event (M 5.6) has imparted maximum peak dynamic stress and cumulative seismic moment a month before the avalanche. Interestingly the avalanche occurred within the seismic coda of M2.8 earthquake from Hindu Kush region, located at 560 km distance. Although the size and its expected impact on avalanche might be minor but its role in instantaneous triggering cannot be ruled out. Even smaller events at larger distance have been reported to cause snow avalanches in same environments. The presence of cracks within the avalanche, were further weaken by persistence of extremely low temperature (lowest in the past decade), causing high precipitation rate along with altering the mechanical properties of the weak layer within the snow pack. Robust wind pressure pattern highest and lowest in March and April, 2012 respectively might be responsible for abrupt changes in loading conditions.

Regional Multifractal Variability of the Overall Seismic Activity in Pakistan from 1820 to 2020 via the Application of MDFA on Earthquake Catalogs

“…These areas are from south to north: The Salt Range, the Potwar and Kohat plateaus, the Hill Ranges, the intermontane basins, the southern Kohistan Ranges, the Nanga-Parbat-Haramosh regions, the Main Mantle Thrust, and the Kohistan island arc, which is separated from Asian rocks of the Pamirs to the north by the Main Karakorum Thrust. Seismically north Pakistan is very active and the faults within fold-and-thrust belt have been frequently producing moderate to large seismic events that include the M w = 7.6 Kashmir earthquake of 2005 that resulted in more than 75,000 lives loss in addition to a colossal economic loss [43][44][45][73][74][75][76][77][78].…”

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“…At least in the western Himalayan region, Ballesteros-Cánovas et al ( 2018) suggest, based on an extrapolation of reconstructed trends, that climate warming will continue to increase the hazard of avalanches, as warmer air temperatures in winter and early spring favour the more frequent occurrence of large, wet snow avalanches, which are able to reach populated valley bottoms. Devastating high elevation snow, or mixed snow-ice avalanches in Langtang, Nepal and Gayari, Pakistan (Fujita et al, 2017;Saif et al, 2022) highlight the particular threat of earthquakes occurring during periods of heavy snow loading. Extremely heavy precipitation events are expected to become more frequent in the future.…”