Space Geodetic Measurements of Plate Boundary Deformation in the Western U.S. Cordillera

Abstract

We have combined space geodetic observations from a variety of sources including continuous Global Positioning System (GPS), campaign GPS, very long baseline interferometry (VLBI), satellite laser ranging (SLR), and DORIS with the objective of observing the large scale pattern of diffuse continental plate boundary deformation across the Pacific-North America plate boundary zone in the western U.S. Cordillera. We employed a distributed processing approach that makes efficient use of computer resources, while producing velocity estimates for all geodetic stations with one common reference frame. We investigated the errors in the resulting velocity estimates by comparing them among different space geodetic techniques at collocated stations, assessing the fit of a rigid North America plate model to the space geodetic velocity estimates, and assessing the sensitivity of the North America plate fixed reference frame realization to the sites that were selected to define it. We found that a value of about 1 mrn/yr is representative of the overall level of uncertainty in the site velocities. The velocity results, as well as a reference frame analysis tool, are available via URL http://cfa-www. harvard.edu/space_geodesy/WUSC/. Updated velocity solutions will be made available through this web site as more data are assimilated. al., 1993]. Foremost among the problems to be addressed were (1) the uniformity of plate rates through geologic time, (2) the rigidity of the plates themselves, and (3) the kinematics of the diffuse zones of deformation separating some plates [Stein, 1993]. Indeed, the rapid development of modern space geodetic techniques over the last two decades in many ways testifies to the importance of such constraints on our understanding of the dynamics of Earth.By the mid-1980's the techniques of satellite laser ranging (SLR) and very long baseline interferometry (VLBI) had provided the first determinations of the contemporary motions of the plates [e.g. Christodoulis et al., 1985; Herring et 28 WESTERN U.S. PLATE BOUNDARY KINEMATICS FROM SPACE GEODESY al., 1986]. Subsequent comparisons of space geodetic measurements with models for plate motions such as NUVEL-1 [e.g., DeMets et al., 1990] demonstrated remarkable steadiness in the relative motions among many plates over time scales of millions of years [e.g., Clark et al., 1987; Smith et al., 1990; Argus and Gordon, 1990]. As the precision of the velocity estimates increased Over time, as more observations were made, and as error sources were discovered and mitigated, space geodetic investigations into the rigidity of the plate interiors, likewise, provided confirmation that intraplate deformation is indeed quite small relative to interplate motions [Argus and Gordon, 1996; Gordon, 1998]. By 1990 the then new technique of radio interferometry using the Global Positioning System (GPS) was undergoing rapid development and promised the possibility of inexpensive and easy to obtain measurements [Segall and Davis, 1997]. The kinematics of plate boundary deformatio...

Oceanic Isostasy: Seafloor Spreading and Rift Localization

“…Even 'narrow' single-valley extensional boundaries like the Main Ethiopian Rift (Corti, 2009) and Rio Grande Rift (Hudson and Grauch, 2013) are several tens of kilometers wide and 3:1 being a high length to width aspect ratio for individual basins. Continental strike slip boundaries like the San Andreas can be 100km or more wide (Bennett et al, 2002;Thatcher, 1995). In contrast, oceans tend to more closely adhere to the plate tectonic assumptions of rigid interiors and narrowly confined boundaries.…”

Oceanic Isostasy: Seafloor Spreading and Rift Localization

“…Even 'narrow' single-valley extensional boundaries like the Main Ethiopian Rift (Corti, 2009) and Rio Grande Rift (Hudson and Grauch, 2013) are several tens of kilometers wide and 3:1 being a high length to width aspect ratio for individual basins. Continental strike slip boundaries like the San Andreas can be 100km or more wide (Bennett et al, 2002;Thatcher, 1995). In contrast, oceans tend to more closely adhere to the plate tectonic assumptions of rigid interiors and narrowly confined boundaries.…”

Evaluation of the Evolving Stress Field of the Yellowstone Volcanic Plateau From 1988 to 2010 From Earthquake First Motions Inversion

“…GPS data from about 160 stations, supported by the UNAVCO, a non-profit university-governed consortium that facilitates geoscience research and education using geodesy, were acquired in many surveys throughout the years. GPS velocities were determined by calculating changes in station coordinates over time and were constrained to a North America fixed reference frame (Bennett et al, 2001), where it is assumed that no deformation happens in the U.S.…”