Jordan Aaron

Case Study: Oso, Washington, Landslide of March 22, 2014-Material Properties and Failure Mechanism

AbstractThis paper describes investigation, testing, analysis, and slope history used to determine the two-phase failure mechanism involved in the 2014 landslide near Oso, Washington. The first pha...

A non-hydrostatic model for the numerical study of landslide-generated waves

This paper proposes and demonstrates a two-layer depth-averaged model with non-hydrostatic pressure correction to simulate landslide-generated waves. Landslide (lower layer) and water (upper layer) motions are governed by the general shallow water equations derived from mass and momentum conservation laws. The landslide motion and wave generation/propagation are separately formulated, but they form a coupled system. Our model combines some features of the landslide analysis model DAN3D and the tsunami analysis model COMCOT and adds a non-hydrostatic pressure correction. We use the new model to simulate a 2007 rock avalanche-generated wave event at Chehalis Lake, British Columbia, Canada. The model results match both the observed distribution of the rock avalanche deposit in the lake and the wave run-up trimline along the shoreline. Sensitivity analyses demonstrate the importance of accounting for the non-hydrostatic dynamic pressure at the landslide-water interface, as well as the influence of the internal strength of the landslide on the size of the generated waves. Finally, we compare the numerical results of landslide-generated waves simulated with frictional and Voellmy rheologies. Similar maximum wave run-ups can be obtained using the two different rheologies, but the frictional model better reproduces the known limit of the rock avalanche deposit and is thus considered to yield the best overall results in this particular case.

Dynamics of the Bingham Canyon rock avalanches (Utah, USA) resolved from topographic, seismic, and infrasound data

The 2013 Bingham Canyon mine rock avalanches represent one of the largest cumulative landslide events in recorded U.S. history, and provide a unique opportunity to test remote analysis techniques for landslide characterization. Here we combine aerial photogrammetry surveying, topographic reconstruction, numerical runout modeling, and analysis of broadband seismic and infrasound data to extract salient details of the dynamics and evolution of the multi-phase landslide event. Our results reveal a cumulative intact-rock source volume of 52 Mm3, which mobilized in two main rock avalanche phases separated by 1.5 h. We estimate the first rock avalanche had 1.5-2 times greater volume than the second. Each failure initiated by sliding along a gently-dipping (21°), highly-persistent basal fault before transitioning to a rock avalanche and spilling into the inner pit. The trajectory and duration of the two rock avalanches were reconstructed using runout modeling and independent force-history inversion of intermediate-period (10-50 s) seismic data. Intermediate- and shorter-period (1-50 s) seismic data were sensitive to intervals of mass redirection and constrained finer details of the individual slide dynamics. Back-projecting short-period (0.2-1 s) seismic energy, we located the two rock avalanches within 2 and 4 km of the mine. Further analysis of infrasound and seismic data revealed that the cumulative event included an additional 11 smaller landslides (volumes ~104-105 m3), and that a trailing signal following the second rock avalanche may result from an air-coupled Rayleigh wave. Our results demonstrate new and refined techniques for detailed remote characterization of the dynamics and evolution of large landslides.

Oso, Washington, Landslide of March 22, 2014: Dynamic Analysis

AbstractThis paper describes and explains the spectacular mobility of the 2014 Oso landslide, which was the cause of its fatal consequences. A geomorphic interpretation of the site conditions is us...

Reconstruction of the 550 x106 m3 Molveno rock avalanche

With an estimated source volume of 550 x106 m3, the Molveno rock avalanche is one of the largest in the Trento Dolomites. Two source areas have been suggested one to the west at Mt. Soran and one to the east at Mt. Gazza. Conversely, some authors suggest the presence of two landslides one from each of the source areas. Rock avalanche debris dammed the gorge between the Molveno Valley to the north and the Nembia Valley to the south forming the Molveno Lake (823 m a.s.l.) (Sauro and Zampieri, 2001; Chinaglia and Fornero, 1995). Here we present results of a study aimed at better constraining the events leading up to the emplacement of this massive deposit on the valley floor. We improve constraints on the extent and volume of the deposit using a combination of GIS, field mapping, and literature review (including results from earlier geophysical investigations). This is then compared to volume calculations from the preferred Mt. Soran source area using a 3D model developed using a combination of Google Earth and standard GIS tools. In order to improve confidence in our assumed source area, we transfer our modelled pre-failure topography to DAN3D, a continuum dynamic model designed to analyze the runout of highly mobile landslides. Although calibrating the parameters for DAN3D requires a back-analysis of the landslide runout, we obtain a reasonably good fit between the modelled and observed deposits using our assumptions of a single event from Mt Soran. Surface exposure dating from a number of boulders located on top of the deposit allow us to better constrain the timing of the event.

Back Analysis of Johnsons Landing 2012 Landslide Using Two Dynamic Analysis Models

The Johnsons Landing landslide occurred on July 12th 2012 in the mid-morning along Gar Creek, that flows from the Kootenay Joe Ridge to the Kootenay Lake, in the south-eastern British Columbia (Canada); it consisted of a debris avalanche with a volume of 300,000 m3. The event caused extensive damage in the area and killed four people. The aim of this work is to summarize the back-analysis of this event with the two dimensional computer-based model DAN-W and the three dimensional model DAN3D. The results constitute a step in the calibration procedure of the DAN-W and DAN3D models, that represent powerful tools in the frame of landslide risk management. Additionally, the issue of the level of topography smoothing which is necessary to obtain reliable results using a dynamic analysis model is highlighted.