HR: 0800h
AN: G11A-1179    [Abstracts]
TI: Analysis of the 1995 and 2005 La Conchita, CA Landslides using Aerial Photographs and ASTER Satellite data
AU: * Schiek, C G
EM: schiek@geo.utep.edu
AF: University of Texas at El Paso, Department of Geological Sciences; 500 W. University Ave., EL Paso, TX 79902 United States
AU: Hurtado, J M
EM: hurtado@geo.utep.edu
AF: University of Texas at El Paso, Department of Geological Sciences; 500 W. University Ave., EL Paso, TX 79902 United States
AB: La Conchita is a small Pacific coastal community that lies between Santa Barbara, CA and Ventura, CA. This area has experienced two massive landslides in the past decade: March 4, 1995, and January 10, 2005. The 1995 landslide had a horizontal length, vertical length, and depth of 120 x 330 x 30 m and covered approximately 10 acres with a volume of 1.3x10⁶ m³. The 2005 landslide was about one-sixth the size of the 1995 landslide and occurred in the southeastern portion of the 1995 landslide deposit. The 2005 landslide measured 350 x 90 m and moved approximately 200,000 m³ of earth. Both of these landslides were caused by heavy rainfall during the rainy season in the area. For 1995 this amount was 761 mm measured from October 1, 1994 to March 3, 1995 at Ojai, CA (20 km northeast of La Conchita). For comparison, this area has a normal mean seasonal rainfall of 390 mm. In 2005, 493 mm was measured from October 1, 2004 to January 10, 2005 at Ventura, CA (20 km southeast of La Conchita), of which 378 mm occurred between December 27, 2004 and January 10, 2005. For comparison, the normal mean seasonal rainfall for Ventura is 122 mm. The heavy rainfall, along with the poorly indurated marine sediments comprising the country rock of the La Conchita area, are thought to be critical factors in why these landslides occurred. This study analyzes the movement of these two landslides using digital terrain change detection techniques with aerial photographs and ASTER satellite images. This technique uses sets of images, one before and one after the terrain change occurred, in the Fourier domain to find the greatest difference between the two images. This difference is the terrain change, and is displayed on the before image as a vector representing the direction and magnitude of horizontal terrain displacement. The La Conchita landslides are well characterized and provide an opportunity for validating our monitoring capability using change detection. The terrain change detection procedure has the capability to measure the distance that the landslide has moved as well as the volume that was transported along that distance. These parameters are important for the mitigation of potential landslide hazards and the assessment of landslide damage. A comparison of the terrain change detection results to the occurrence of landslides in the area and precipitation records for the area may provide also some predictive capability
DE: 1211 Non-tectonic deformation
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
DE: 1625 Geomorphology and weathering (0790, 1824, 1825, 1826, 1886)
SC: Geodesy [G]
MN: Fall Meeting 2005