David Verdonck1
Several recent studies have suggested that the Cascadia Subduction zone may be locked in more than one location. When the subduction interface contains multiple locked sections the traditional elastic dislocation analogy breaks down. Other modeling methods such as finite element or boundary element methods may be required to accurately represent the interseismic deformation associated with this type of complex plate boundary. In an effort to develop a better analog for the interseismic subduction process, several models are compared. Results indicate that vertical deformation sensitive to the modeling technique while horizontal deformation is not. As a consequence of this result, a better understanding of the active vertical deformation is required.
Leveling is a time tested precise geodetic technique. Data from over 500 leveling lines passing through Oregon and Washington are archived by the United States National Geodetic Survey. Many locations have been surveyed multiple times over the past 80 years. Precise changes in relative elevation can be determined from analysis of data from repeated leveling lines. Data from leveling conducted along the Columbia River during the 1920s, 1940, 1960s, and 1980s are analyzed to determine relative uplift rates. Preliminary results indicate that in some regions the relative rate of vertical crustal deformation varies over time.
1SUNY Geneseo, Geneseo, New York
dverdonck@stny.rr.com