Articles | Volume 15, issue 6
Nat. Hazards Earth Syst. Sci., 15, 1265–1273, 2015
https://doi.org/10.5194/nhess-15-1265-2015
Nat. Hazards Earth Syst. Sci., 15, 1265–1273, 2015
https://doi.org/10.5194/nhess-15-1265-2015

Research article 17 Jun 2015

Research article | 17 Jun 2015

Dynamics of the Oso-Steelhead landslide from broadband seismic analysis

C. Hibert, C. P. Stark, and G. Ekström C. Hibert et al.
  • Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY, USA

Abstract. We carry out a combined analysis of the short- and 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 remote-sensing 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 × 106 and 10 × 106 m3, in agreement with estimates from ground observations and lidar mapping.

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We carry out a study of the seismic signals generated by the devastating Oso-Steelhead landslides. We invert the long-period seismic signals generated by the first main event and obtain estimates of its trajectory, kinematics and mass. No distinct long-period surface waves were recorded for the second failure, which prevents inversion for its source parameters. However, from the comparison of the energy of the short-period waves generated by both events, we can estimate the volume of the second.
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