Using LiDAR Data Visualization to Investigate Origin of Uphill-Facing Scarps in Mountains, Alaska

Light Detection and Ranging (LIDAR) is a fast method for sampling the earth’s surface with a high density and high accuracy point cloud that is used to generate high density and high accuracy Digital Elevation Models (DEMs) and DSMs. In this research we obtained airborne LIDAR elevation data with spatial resolution of 1 m to reveal new details of mountain block morphology and structure to investigate the origin of uphill facing scarps. Quaternary fault scarps occur in several mountain blocks in the western Saint Elias and Eastern Chugach Mountains of southern Alaska. Possible mechanisms for formation of these scarps include deformation caused by active folding, or deformation caused by gravitational loading and strong ground motion during earthquakes. The field observations and LIDAR visualization lead us to propose a three-stage model for flexural toppling. Failure is by flexural toppling, with rotation and shearing of bedding planes under the influence of gravity where bedding dips steeply into the mountain side. Down-slope bending of bedding surfaces may initiate formation of a basal sliding surface beneath the toppled beds, leading to landsliding down slope. However, horizontal acceleration caused by strong ground motion enhances the probability of failure by flexural toppling, especially in the upper parts of mountain slopes, where ground motion is amplified.

[1]  J. Bray,et al.  Toppling of Rock Slopes , 1977 .

[2]  S. P. Anderson,et al.  Orogenic and glacial research in pristine southern Alaska , 2001 .

[3]  E. Hoek,et al.  Rock slope engineering , 1974 .

[4]  Terry L. Pavlis,et al.  Deformation during terrane accretion in the Saint Elias orogen, Alaska , 2004 .

[5]  J. McCalpin,et al.  Active Tectonics of Western Saint Elias Orogen, Alaska: Integration of LIDAR and Field Geology , 2006 .

[6]  G. Plafker,et al.  Geologic map and cross-sections of the Cordova and Middleton Island quadrangles, southern Alaska , 1981 .

[7]  The Institution of Mining and Metallurgy , 1956, Nature.

[8]  Ulf Zischinsky,et al.  On the deformation of high slopes , 1966 .

[9]  James P. McCalpin,et al.  Chapter 5 Paleoseismology of Compressional Tectonic Environments , 1996 .

[10]  Jeffrey T. Freymueller,et al.  Active tectonics and seismic potential of Alaska , 2008 .

[11]  M. Meghraoui,et al.  Active faulting in the western Pyrénées (France): Paleoseismic evidence for late Holocene ruptures , 2005 .

[12]  G Crosta,et al.  Landslide, spreading, deep seated gravitational deformation: analysis, examples, problems and proposals , 1997 .

[13]  Travis Hudson,et al.  Surface features and recent movement along the Ragged Mountain fault, south-central Alaska , 1976 .

[14]  J. Moore,et al.  Geology of the southern Alaska margin , 1994 .

[15]  W. Z. Savage,et al.  Topographic and structural conditions in areas of gravitational spreading of ridges in the Western United States , 1989 .