Seismic Collapse Mechanisms of Large (M~4) Rock and Ice Avalanches in Southeast Alaska
Description:
Mass movement events such as landslides and rock and ice avalanches are traditionally analyzed at seismological observatories as single forces that model mass trajectories unfolding in space and time. These events may also be analyzed as point sources with moment tensors, though this approach may not always apply for complex events with tortuous runout trajectories, multiple simultaneous detachments, slow slip, and emergent signals. Despite their complexity, these events may also produce a more coherent long-period signal which in the far field may be analyzed with moment tensors. When applicable, moment tensor analysis of landslides provides a way to routinely and quickly characterize mass movement events which can aid in providing prompt response and warning. In the present study we examine a dataset of seismic events in Alaska identified as icequakes or avalanches by the Alaska Earthquake Center and estimate the source mechanisms (moment tensors) of five events from the recorded waveform data. These five events occurred in the Southeast Alaska between 2005-2016 and were massive rock and ice avalanches with reported volumes on the order of 30-60 million m3, weighing between 20-100 billion kg. Due to the large size, these events were observed at seismic stations located thousands of kilometers away. Some events occurred during deployment of the USArray network in Alaska and Canada which allowed us to examine datasets containing hundreds of stations. The best fitting solutions produce synthetics seismograms that agree with long-period observational data. We analyze the moment tensors in terms of their source-types, which reveal negative isotropic (collapse or dilatational) parameters, and we discuss these and other gravitational mass movements from mining sites. We also discuss work towards operational implementation for routine analysis of similar events.
Session: Detecting, Characterizing and Monitoring Mass Movements - III
Type: Oral
Date: 5/2/2024
Presentation Time: 02:00 PM (local time)
Presenting Author: Celso
Student Presenter: No
Invited Presentation:
Authors
Celso Alvizuri Presenting Author Corresponding Author celso.alvizuri@norsar.no Norwegian Seismic Array |
Natalia Rupper naruppert@alaska.edu University of Alaska Fairbanks |
Ezgi Karasozen ekarasozen@alaska.edu University of Alaska Fairbanks |
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Seismic Collapse Mechanisms of Large (M~4) Rock and Ice Avalanches in Southeast Alaska
Category
Detecting, Characterizing and Monitoring Mass Movements