Herein, we present results obtained from time-lapse imagery acquired by a digital single-lens reflex camera during 2014–18 used to monitor the Planpincieux Glacier on the Italian side of the Grandes Jorasses (Mont Blanc massif). We processed the images using image cross-correlation to measure the surface kinematics of the most active lobe of the glacier that presents a high velocity and frequent ice detachments. During the monitoring, we observed two or three periods of sharp acceleration per year that culminated with large break-offs followed by analogous decelerations. Overall, we registered more than 350 failures with a volume >100 m3, of which, 14 events had volumes larger than 10 000 m3. The study identified a monotonic positive relationship between the velocity and failure volume that may be used to estimate the volume of the collapses before an event. We identified the thresholds of velocity and acceleration that characterise the activation of the speed-up periods. The study allowed the characterisation of three different instability processes that lead to the break-off of ice chunks from the glacier terminus: (i) disaggregation, (ii) slab fracture and (iii) water tunnelling failure which can be differentiated based on the rheology, the volume involved and the trigger process.

中文翻译：

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使用摄影延时分析的 Planpincieux 冰川断层的分类和运动学

在这里，我们展示了从 2014-18 年期间由数字单镜头反光相机获取的延时图像获得的结果，该相机用于监测 Grandes Jorasses（勃朗峰地块）意大利一侧的 Planpincieux 冰川。我们使用图像互相关处理图像，以测量冰川最活跃的叶的表面运动学，该叶呈现出高速和频繁的冰脱离。在监测期间，我们观察到每年有两到三个时期的急剧加速，最终导致大的中断，然后是类似的减速。总体而言，我们记录了超过 350 次故障，体积 >100 m3, 其中 14 个事件的体积大于 10 000 m3. 该研究确定了速度和破坏体积之间的单调正相关关系，可用于估计事件前塌陷的体积。我们确定了表征加速期激活的速度和加速度阈值。该研究允许表征三种不同的不稳定性过程，这些过程导致冰块从冰川末端断裂：（i）分解，(二)板片断裂(iii)水隧道失败这可以根据流变学、涉及的体积和触发过程来区分。