HR: 14:55h
AN: S43D-06    [Abstracts]
TI: Uplift and subsidence along the Cascadia subduction zone determined from historical repeated leveling
AU: * Verdonck, D
EM: dverdonck@eglab.org
AF: Eastern Geodynamics Lab, 60 Larchmont Rd, Elmira, NY 14905
AB: A better understanding of the vertical crustal deformation throughout the Pacific Northwest of the United States will help model coupling along the plate boundary and eventually help us better assess the earthquake potential in the region. In this study, I examine historical leveling data from Cascadia and calculate uplift rates throughout the region. Vertical deformation rates are calculated from historical differential leveling. I calculate rates by taking the difference between elevations at common benchmarks and dividing by the time between surveys. I remove outliers based on a median absolute deviation technique. The uplift rates are adjusted using a least squares procedure based on a bivariate cosine series basis function. Uplift rates calculated from tide gauges (Weldon, personal communication) were included in the adjustment and held fixed, thereby making sea-level a common datum. Once outliers are identified and the data adjusted to a common datum, I smooth the data using an iterative, robust, weighted, moving average technique. The results indicate landward tilting in several regions along the coast alternating with regions of little or no deformation. There were no regions with seaward tilting. In some regions the coastal uplift continues inland but landward tilting appears to dominate the deformation. The rate of landward tilting varies significantly along the coast with the fastest deformation occurring to the north. At about 45\deg N, there is little vertical deformation either at the coast or inland. The lack of vertical deformation across central Oregon may represent a transition in subduction behavior between northern and southern segments.
DE: 8110 Continental tectonics--general (0905)
DE: 8120 Dynamics of lithosphere and mantle--general
DE: 7205 Continental crust (1242)
SC: Seismology [S]
MN: 2004 AGU Fall Meeting