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The Seismic Puzzles of the 2022 Chaos Canyon Landslide in Rocky Mountain National Park

Description: 

On 28 June 2022, ~2 million m³ of ice-rich debris mobilized from the southeast flank of Hallett Peak in Rocky Mountain National Park, sliding about 245 m in ~2 minutes, and narrowly missing a group of climbers downslope in Chaos Canyon. The size and energy of this event was evident in eyewitness videos and reflected in the ground vibrations it generated, recorded up to 70 km away. Using eyewitness accounts, field and remote sensing techniques, historic climate data, and seismic evidence, we pieced together a detailed timeline of this landslide stretching back decades to when the slope started moving as air temperatures warmed. In this talk, we focus on June 28, and on the seismic aspects of the landslide event.

We first describe how we used the seismic signals and eyewitness accounts to piece together a complex sequence of events starting with a gradual build-up in rock fall activity and culminating in three energetic sliding episodes. We also discuss a seismic “red herring”: a M1.4 earthquake-like signal ~1 min prior to the main sliding event that initially appeared to be coming from the landslide, but that later evidence, including a repeating earthquake analysis, revealed to be a blast from reservoir construction 36 km east of the park. Videos show some sliding was already underway when the blast occurred making it unlikely that it triggered the slide, but the weak shaking it induced at the landslide (~0.001% g) could have influenced slide behavior. Finally, we investigated why the main event did not generate observable long-period seismic signals related to bulk mass accelerations that are typical of large, rapid landslides by modeling the event using the SHALTOP numerical landslide model. We found that this landslide was actually slower and less mobile than most landslides of similar size, resulting in long-period signals that were too low amplitude to be observable. In summary, we combined diverse evidence and techniques to understand this event, and the seismic signals were valuable in helping unravel this unusual landslide sequence.

Session: Detecting, Characterizing and Monitoring Mass Movements - III

Type: Oral

Date: 5/2/2024

Presentation Time: 02:15 PM (local time)

Presenting Author: Kate

Student Presenter: No

Invited Presentation: 

Authors