HR: 15:10h
AN: G53A-07    [Abstracts]
TI: Spatial and Temporal Characterization of the Portuguese Bend Landslide, California, Using InSAR
AU: * Calabro, M
EM: mcalabro@uoregon.edu
AF: University of Oregon, Department of Geological Science, 1272 University of Oregon, Eugene, OR 97403, United States
AU: Schmidt, D
EM: das@uoregon.edu
AF: University of Oregon, Department of Geological Science, 1272 University of Oregon, Eugene, OR 97403, United States
AU: Roering, J
EM: jroering@uoregon.edu
AF: University of Oregon, Department of Geological Science, 1272 University of Oregon, Eugene, OR 97403, United States
AU: Douglas, R
EM: rdouglas@usc.edu
AF: University of Southern California, 3651 Trousdale Parkway, Los Angeles, CA 90089, United States
AB: Here we use InSAR and GPS data to spatially and temporally constrain deformation of the Portuguese Bend Landslide, and correlate movement with seasonal rainfall. The Portuguese Bend Landslide on the Palos Verdes peninsula in southern California has been sliding at a rate of several meters per year since the late 1950's. Earlier work has shown that displacement varies greatly from season to season, with high values occurring during the winter and relatively low values in the summer. Our findings suggest that the landslide continues to move at rates comparable to those found in previous studies. With data collected from European ERS satellites over tracks 170 and 442 between June 1992 and November 2000, we use the ROI_PAC software package to process more than 500 interferograms of the region. The interferograms show a wide variation in phase coherence, with the greatest coherence occurring during the dry summer months when deformation is the slowest. We do not expect winter interferograms to be coherent over the sliding area as the displacement rate is too large to be measured with conventional techniques. Stacking the 22 summer interferograms, we determine the line-of-sight displacement rate during the summer months to average 50±36 mm/yr. The large deviation is due to yearly changes in displacement rate. Additionally, we stack the incoherent areas in the winter months by counting how often each pixel is coherent to create a qualitative spatial map of high deformation. While this stack does not yield a displacement rate for the winter months, it constrains the extent of the slide and suggests that it is confined to the previously mapped region. The map of phase coherence also constrains the initiation and cessation of fast ground motion to the months of December through April. This corresponds to the rainy season, during which displacement rate increases via infiltration and pore pressure generation within the slide mass. We also analyze existing GPS data for the region, spanning the same time interval and area as the InSAR data. The InSAR result for the magnitude of the phase change in the summer months is validated by reducing the three component GPS data to the satellite's line-of-sight. Combining InSAR and GPS with rain gauge data, our long term objective is to better understand the mechanical and hydrological properties of the Portuguese Bend Landslide and monitor its activity over the past decade.
DE: 1211 Non-tectonic deformation
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
DE: 1810 Debris flow and landslides
DE: 1895 Instruments and techniques: monitoring
DE: 6924 Interferometry (1207, 1209, 1242)
SC: Geodesy [G]
MN: 2007 Fall Meeting