Dynamics of the Bingham Canyon Mine landslides from seismic signal analysis

Abstract

Joint interpretation of long‐ and short‐period seismic signals generated by landslides sheds light on the dynamics of slope failure, providing constraints on landslide initiation and termination and on the main phases of acceleration and deceleration. We carry out a combined analysis of the seismic signals generated by two massive landslides that struck the Bingham Canyon Mine pit on 10 April 2013. Inversion of the long‐period waveforms yields time series for the bulk landslide forces and momenta, from which we deduce runout trajectories consistent with the deposit morphology. Comparing these time series with the short‐period seismic data, we are able to infer when and where major changes take place in landslide momentum along the runout path. This combined analysis points to a progressive fracturing of the masses during acceleration indicates that deceleration starts the moment they reach the pit floor and suggests that the bulk movement is stopped by a topographic barrier.

Dynamics of the Oso-Steelhead landslide from broadband seismic analysis

“…This is consistent with results from other well-recorded landslides (e.g. Hibert et al, 2014). The absence of earlier short-period signal at JCW further supports our inference that the forces during "interval 1" discussed by Iverson et al (2015) are spurious.…”

“…These two amplitude peaks are not visible in the 3-10 Hz band. In a previous study (Hibert et al, 2014), we observed that seismic signals produced by the two major landslides during the Bingham Canyon open-pit mine collapse exhibited amplitude peaks that originated in the flowing mass hitting topographical barriers and that were stronger in the 1-3 Hz frequency band than in the 3-10 Hz band. This observation points to a potential higher sensitivity of the 1-3 Hz frequency band to topographical effects, and prompts the interpretation that the two peaks observed for the second Oso-Steelhead event might have been generated as sliding and flowing debris encountered topographic obstacles.…”

“…Once peak acceleration of the centre of mass was reached, a lowamplitude short-period signal emerged from the noise. This delay suggests fragmentation of the initially intact mass while it was already accelerating on the slope (Allstadt, 2013;Hibert et al, 2014). At that point, the magnitude of acceleration along the trajectory started to decrease.…”

“…The combined analysis of short-period seismic data with the dynamics inferred from long-period waves provides important information on large landslide motion (Schneider et al, 2010;Yamada et al, 2013;Allstadt, 2013;Hibert et al, 2014). While the long-period waves and the force-history (LFH) inversion provide insight into the temporal evolution of the bulk momentum of the whole landslide mass, the shortperiod waves reflect spatially complex momentum exchanges across the basal slide area at shorter length scales.…”

“…In recent years, seismology has proven useful in this regard by offering a way to infer the dynamics of large mass movements (e.g., Brodsky et al, 2003;Favreau et al, 2010;Schneider et al, 2010;Moretti et al, 2012;Yamada et al, 2013;Allstadt, 2013) and estimate important properties such as the mobilized mass (Ekström and Stark, 2013). Additional analysis of the short-period waves provides an extra constraint on source mechanisms and a more complete understanding of the dynamics of slope failures (e.g., Suriñach et al, 2005;Deparis et al, 2008;Vilajosana et al, 2008;Dammeier et al, 2011;Hibert et al, 2011Hibert et al, , 2014.…”