Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY, USA
Received: 12 Nov 2014 – Discussion started: 05 Dec 2014
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.
Revised: 14 May 2015 – Accepted: 21 May 2015 – Published: 17 Jun 2015
Hibert, C., Stark, C. P., and Ekström, G.: Dynamics of the Oso-Steelhead landslide from broadband seismic analysis, Nat. Hazards Earth Syst. Sci., 15, 1265-1273, doi:10.5194/nhess-15-1265-2015, 2015.