{"id":8921,"date":"2017-10-09T11:14:34","date_gmt":"2017-10-09T09:14:34","guid":{"rendered":"https:\/\/wp.unil.ch\/geoblog\/2017\/10\/analyse-des-recentes-chutes-de-blocs-dans-la-paroi-del-capitan-par-le-groupe-danalyse-du-risque-en-collaboration-avec-le-parc-national-du-yosemite\/"},"modified":"2023-11-20T11:58:57","modified_gmt":"2023-11-20T10:58:57","slug":"the-recent-el-capitan-rockfalls-have-been-analyzed-by-the-risk-analysis-group-in-collaboration-with-yosemite-national-park","status":"publish","type":"post","link":"https:\/\/wp.unil.ch\/geoblog\/en\/2017\/10\/the-recent-el-capitan-rockfalls-have-been-analyzed-by-the-risk-analysis-group-in-collaboration-with-yosemite-national-park\/","title":{"rendered":"The recent El Capitan rockfalls have been analyzed by the Risk Analysis Group in collaboration with Yosemite National Park"},"content":{"rendered":"
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Michel Jaboyedoff,<\/a> Institute of Earth Sciences (ISTE)<\/figcaption><\/figure>\n\n\n\n

Assessment of rockfall susceptibility is a difficult task because numerous processes contribute to make the rock mass unstable.<\/strong><\/p>\n\n\n\n

The Risk Analysis Group <\/a>of the Institute of Earth Sciences of the University of Lausanne has been working for several years to improve the forecasting of such events. Since 2010, several PhD students and researchers of the group have worked on rockfalls in Yosemite National Park.<\/p>\n\n\n\n

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This research, funded by the Swiss National Science Foundation, is performed collaboratively with Dr. Greg M. Stock, Yosemite Park\u2019s geologist of the United States National Park Service (USNPS) and Dr. Brian D. Collins of the Landslide Hazards Program of the U.S. Geological Survey (USGS).<\/p>\n\n\n\n

The recent rockfall events (Figure 1) that occurred on the southeast face of El Capitan rock formation caused one fatality and several injuries (refer to the New York Times, the New York Times<\/em>, the Mercury News<\/em> and the National Park Service<\/em>). These rockfall events have been analyzed in detail (Figure 2) by the Risk Analysis Group and in particular by Antoine Guerin, a fifth-year PhD student. Antoine has provided the first estimations of the collapsed volumes (450 m3<\/sup> and 10\u2019250 m3<\/sup>) by comparing the terrestrial laser scans acquired over several years with new post-event photogrammetric models built with photos taken by Dr. Stock on 27 and 28 September.<\/a><\/p>\n\n\n\n

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Figure 1: Before-after comparison of the 28 September 2017 rockfall event. The top photo shows the scar (bottom center) of the 27 September 2017 rockfall event, as well as the one of 11 June 2014 (details in Figure 2). (Photo credit: U.S. National Park Service)<\/figcaption><\/figure>\n<\/div>\n\n\n\n
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Figure 2: Location of the scars of the 27-28 September 2017 rockfall events with their associated estimated volumes. Data sources: 2006 & 2010 airborne LiDAR by the National Center for Airborne Laser Mapping (NCALM); 2015 terrestrial LiDAR & 2017 Structure-from-Motion (SfM) models by the Risk Analysis Group; SfM pictures taken by Dr. Stock (credit: U.S. National Park Service).<\/figcaption><\/figure>\n<\/div>\n<\/div>\n\n\n\n

In Yosemite Valley, Drs. Collins and Stock have shown that thermal forcing and solar radiation play a major role in the destabilization and rupture of large granitic rock slabs (See Collins and Stock, 2016, in Nature Geoscience and this video of exfoliating rock from YouTuber dotysan).<\/p>\n\n\n\n

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