Dynamics of the Oso-Steelhead landslide from broadband seismic analysis

Abstract

Abstract. We carry out a combined analysis of the shortand long-period seismic signals generated by the devastating Oso-Steelhead landslide that occurred on 22 March 2014. The seismic records show that the Oso-Steelhead landslide was not a single slope failure, but a succession of multiple failures distinguished by two major collapses that occurred approximately 3 min apart. The first generated long-period surface waves that were recorded at several proximal stations. We invert these long-period signals for the forces acting at the source, and obtain estimates of the first failure runout and kinematics, as well as its mass after calibration against the mass-centre displacement estimated from remotesensing imagery. Short-period analysis of both events suggests that the source dynamics of the second event is more complex than the first. No distinct long-period surface waves were recorded for the second failure, which prevents inversion for its source parameters. However, by comparing the seismic energy of the short-period waves generated by both events we are able to estimate the volume of the second. Our analysis suggests that the volume of the second failure is about 15-30 % of the total landslide volume, giving a total volume mobilized by the two events between 7 × 10 6 and 10 × 10 6 m 3 , in agreement with estimates from ground observations and lidar mapping.

Dynamics of the Askja caldera July 2014 landslide, Iceland, from seismic signal analysis: precursor, motion and aftermath

“…They reach maximum amplitudes about 45 sec after the signal onset, which coincides with lower acceleration and the transition to decelerated motion in the force history inversion of the propagation phase. We infer from this lag time in the high-frequency signal that the main slope failure along the southeastern caldera wall was a single, large event, starting with aseismic sliding of a relatively coherent mass that gradually fragmented during down-slope 10 acceleration (Allstadt, 2013;Hibert et al, 2015). In this interpretation, the high-frequency signals are caused by the momentum exchanges of block impacts, and frictional processes within the moving slide and along its boundaries, especially when the moving mass traverses small-scale topographic features on the sliding base (cf.…”

“…The rolling, jumping, colliding and impacting blocks created seismic signals with emergent onsets, cigar-shaped envelopes (Dammeier et al, 2011;Allstadt, 2013;Hibert et al, 2015;Moretti et al, 2015) and of higher seismic amplitudes than the 25 background level at the stations closest to the Askja caldera. Such a chain-reaction with subsequent slope collapses is not uncommon after landslides (Iverson et al, 2015).…”

“…Long-period seismic signals of landslides from stations several thousand kilometres away can be used as references for inversions (Allstadt, 2013;Ekström and Stark, 2013;Yamada et al, 2013;Hibert et al, 2015;Chao et al, 2016) or models (Brodsky et al, 2003;Favreau et al, 2010;Schneider et al, 2010;Moretti et al, 2012) to constrain the location, mass, duration, displacement, and run-out 15 trajectories of the landslide. Short-period waves, generated by the momentum exchanges within a granular landslide mass and along its boundaries, have been used to study the detachment, moving and reposing phases of landslides (Norris, 1994;Suriñach et al, 2005;Dammeier et al, 2011;Hibert et al, 2011Deparis et al, 2008;Vilajosana et al, 2008).…”

2014 Canadian Geotechnical Colloquium: Landslide runout analysis — current practice and challenges

“…Significantly, most landslide-related deaths occur on relatively flat land in the distal runout zone (D. Petley, personal communication, 2014), where human development is generally concentrated and high-velocity landslide impacts can still occur, often with little or no advance warning. The landslide that occurred near Oso, Washington, in March 2014, which travelled more than 1 km across the valley bottom and caused 43 fatalities in the community of Steelhead Haven (Keaton et al 2014;Iverson et al 2015;Hibert et al 2015;Wartman et al 2016), is a recent example of this widespread problem. In some cases, agricultural development on the flat land in the runout zone may also contribute to the mobility of landslides and exacerbate the consequences (e.g., Evans et al 2007).…”

Dynamics of the Wulong landslide revealed by broadband seismic records

“…Correspondingly, two approaches have been developed for research on landslides using seismic signals. The first approach uses the short-period signals, usually for spectral analysis and qualitative descriptions; the second approach involves calculating source time functions of the landslide using inversions of long-period seismic records (Ekström and Stark 2013;Hibert et al 2014Hibert et al , 2015Lin et al 2010;Yamada et al 2013;Zhao et al 2015). In this paper, long-period signals extracted from 8 broadband seismic stations within 250 km of the Wulong landslide are used to determine its source time functions.…”